Mechanic: The Sad Cruze · 2:35am Aug 8th, 2018
Locate your favorite beverage, kids, ‘cause it’s time for another mechanicing blog post!
Way back in the day before traning in various fields got more intense, people would be given one problem at a time to solve and thus think that they were prepared. In my experience, things don’t work like that in real life, and not being able to successfully deal with multiple failures in an efficient method can be expensive, or worse.
Supposedly, the guys in the control center at Three Mile Island had trained what to do when one thing went wrong with the reactor, but not what to do when several things went wrong at the same time, and when some of the instruments were lying to them.
Likewise, I could pull any number of NTSB reports where lots of things went wrong with an airplane. Here’s an example: Reeve Aleutian Airways flight 8. The propeller came off the number four engine, which is of course bad. In the process of departing the aircraft, it also went through the fuselage, jamming all the flight controls except the autopilot.
Ultimately, with good teamwork and cojones the size of cantaloupes, the crew successfully landed the airplane at Anchorage, after first executing a missed approach (scary when you have a whole functioning aircraft, to say nothing of one that’s had a propeller go through it) and then opening the fire bottles on all the engines that were still running for their second landing.
Did I say cantaloupes? I meant watermelons.
Anyway, the point is that a lot of times when we’re diagnosing a car, there’s more than one thing wrong. Especially since a lot of people ignore the check engine light until the car won’t run any more.
I once worked on a Cadillac that had a coil failure like that Mercury I blogged about a while back. It also took out the PCM. Wouldn’t have happened if they’d changed the spark plugs sooner.
Of course, they didn’t bring it in then, either, not until the misfire caused it to slag a converter and plug the exhaust, which added about another thousand to the eventual repair bill.
These days, cars are pretty good at monitoring their sensors. I mentioned in a previous blog post how there are now symptom codes and secondary indicators and so forth. That’s actually going to be a bit relevant here.
The vehicle in question was a Chevy Cruze with a 1.4L turbocharged gas engine. It ran kind of okay (compared to some I’ve pulled into the shop [or attempted to]).
I hooked up the scan tool, and this is what I got.
POWERTRAIN CONTROL MODULE (PCM):
P0106-00 MAP performance
P0131-00 HO2S circuit low voltage 1/1
P013B-00 HO2S slow response lean to rich 1/2
P015B-00 HO2S slow response lean to rich 1/1
P0171-00 Bank 1 lean
P0506-00 Idle low
P0507-00 Idle high
P1101-00 Intake Air Flow System Performance
P2270-00 HO2S stuck lean 1/2ANTILOCK BRAKES (ABS):
U0100-71BODY CONTROL MODULE (BCM):
B3883-01
B3883-04POWER STEERING CONTROL MODULE (PSCM):
C056E-45
Let all those codes sink in for a moment. This car is not happy.
In fact, inasmuch as a car’s onboard computers can feel distress, this computer is feeling it. Note above that there’s both a code for idle high and idle low. It can’t be both, can it? Or can it?
The car knows that something’s gone wrong, but it’s not clever enough to figure out exactly what that is.
As an aside, before we get back to the engine, let’s take a minute to discuss the codes we’ve got before us. Back in Ye Olde Times, a PCM might have two-digit codes, and that was it. For years, a code 12 on a GM meant that the cam sensor was broken . . . or the engine wasn’t running (hopefully the tech would be able to determine the difference).
We’ve got here from the PCM P-codes, as expected. P stands for powertrain, the stuff that makes the car go.
The Antilock Brakes have a U-code. That’s a communications code; it means that some module isn’t talking to another. I didn’t write down what it was, because it wasn’t relevant. Usually if there isn’t a hard fault, you ignore communications codes. [You also never know what module talks to what other module; a Ford I worked on today had a code for the Airbag module not talking to the Sync (Infotainment; what you plug your iPhone into) module. Why does the Airbag care what the Sync module is doing?]
Now, you’ll note that the BCM has two B-codes. B, unsurprisingly, means Body. And you’ll also note that the first four digits are the same--that’s because it’s the same system that’s failed. The suffixes tell you the tale. The first one, -01, is license plate lamp high resistance; the second, -04, is license plate lamp circuit open. I can tell without even going to the back of the car that one or more of the license plate lights don’t work. How cool is that!
And finally, the Power Steering Control Module. That’s got a C prefix for Chassis. It’s also a beautiful example of how they’re using hex in codes these days. That’s actually a programming code, it turns out; the Power Steering Control Module is apparently not programmed correctly.
Well, that was fun.
Now back to the powertrain--that’s where we’re going to be focusing our efforts.
Cars have one or two cylinder banks, typically. An inline engine has one, a V-engine or opposed piston engine has two. A rotary engine, I have no idea how they label them. Any Mazda rotary fans, I’d be interested to know.
This car is an inline four, so wherever it says bank 1, that’s the only bank. We don’t have to worry about bank 2. In some ways, that’s a relief; then again, diagnostically, if things are wrong with only one side of the engine and not the other, that can be helpful when diagnosing it.
The easiest way to go through a long list like this is to divide and conquer. Which things might be related? You’ll notice that there are a bunch of codes for oxygen sensors (HO2S [Heated Oxygen Sensor]); could one of them have failed in multiple ways, like the license plate bulbs did? We don’t know how long the check engine light has been on--those codes might have all set as the oxygen sensor was failing.
What about those two idle codes? Too high and too low also suggests that whatever controls the idle is having a bad time. It’s got one job to do, and it seems like it can’t do it.
Once again, we don’t know which code set first here. The only thing that we do know is that they can’t have set simultaneously unless this is some kind of Schrodinger’s engine.
The intake air flow performance might be related to that, too. On a lot of cars, idle speed is set by how much air is allowed into the engine with a closed throttle plate.
I should tell you here before you think that I’m leading you astray that the car did have a bad idle. It wandered up and down and couldn’t cope very well with extra load, like the A/C compressor kicking on. That’s normal for something like my 40-year old Chevy with a one-barrel carburetor, but not so much for a modern car. Especially since it knows it’s about to turn on the A/C and can adjust the idle speed to suit before it even does it.
There are a lot of things that GM does wrong, but one thing that they typically do right is have both a MAF sensor and a MAP sensor. The MAF measures manifold air flow--how much air goes by that sensor and into the engine. The MAP measures pressure (or vacuum) in the intake, and can run the engine if the MAF stops working. In fact, GM cars typically only had a MAP up into the 90s, when they went for more accuracy, keeping the MAP for barometric pressure and for backup fuel strategy*.
[Ford went with just the MAF and heaven help you when it fails. Chryslers still mostly just use a MAP because Chrysler is too busy going bankrupt and getting in bed with AMC Renault Mitsubishi Daimler Fiat.]
Anyway, weird that only one of them’s affected.
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*In case you were curious, the two operation strategies are speed/density (with a MAP) and mass airflow (with a MAF)
Could it be that the MAP sensor went bad?
Engines are basically just air pumps, and they need to know how much air comes in. Not only in volume, but they also need to know density. A car that’s on top of Mt. Everest is going to experience very different operating conditions that one that’s smack in the middle of Death Valley. So one of the things that the MAP does is determine what barometric pressure is, each and every time you turn the car on. If it’s wrong, than all the other calculations that the engine makes will also be wrong.
A really easy example for anyone who knows anything about math--even me--is if someone gives you all the formulas for circles and cylinders and cones. Area, volume, the whole ball of wax.
And then they tell you that pi equals three exactly.
No matter how well you perform those calculations, your end result will be wrong. Sometimes by a little, sometimes by a lot, but it’s always gonna be wrong.
Using that analogy, it now seems likely that there’s a problem at the front of the engine (at least, in terms of airflow), and that’s affecting everything downstream. If the wrong quantity of air comes in, the oxygen sensors--who know how much air there should have been, since the PCM uses that in its calculations--are going to read something that the PCM doesn’t expect. Something that, as far as the computer is concerned, is impossible, and so it’s going to start to set codes for the oxygen sensors, because it doesn’t know what else to do. It’s got a lookup table, and the table says, “If X, then Y, plus or minus 5%” And the computer says, “Hey, this guy’s giving me Z, what’s up with that?” Boom, code sets.
Before we get to the diagnosis, permit me one more aside.
There are three main types of engine codes that we generally concern ourselves with as mechanics.
The first is what’s called a circuit code. That basically means that there isn’t a complete circuit. It’s open, it’s shorted, something’s wrong with it. That license plate lamp code that the BCM set, that’s a circuit code. Electrons can’t get from A to B, so obviously whatever’s in the middle doesn’t work like it should.
The second is a rationality code. That’s where a sensor gives a reading that is either impossible or highly unlikely (and in some cases, those codes can be set when there’s actually nothing wrong with the car, but it usually takes some creativity that the designers never anticipated). A lot of sensors actually check for that before the car even starts, because you’ll have more than one that monitors more or less the same thing. An example I’ve given before is temperature sensors. If the car sits for an extended period of time (let’s say, overnight), every temperature sensor on the car ought to give a very similar reading. If one is way off base, it’s probably wrong. For example, if the intake air temperature sensor says it’s 60, and so does the outside air temperature sensor, and the transmission fluid temperature sensor, but the coolant temperature sensor thinks it’s forty below, the computer knows that it can’t trust what the coolant temperature sensor says.
The final type is a performance code. The thing works, but not like it’s supposed to. A result happens, but late. The idle can be controlled, but it’s too low or too high. The oxygen sensors are switching like they’re supposed to, but they’re taking too long. Some of them even say it flatly in the code description--to save you from having to scroll all the way up this ramble, it had a code for MAP performance and Intake Air Flow System performance.
The lean code is also a performance code--it can make the engine run but it’s outside the window of where it should have to adjust. Generally, the automakers allow fuel trims +/- 25% but I’ve seen them run past 60% (granted, that particular car was not very happy).
The most obvious explanation for all this car’s problems is that the airflow isn’t correct. Assuming that all the sensors are good (I don’t know that, but it’s a good place to start), I check the MAF.
In hindsight, it actually wasn’t as low as I thought. A general rule of thumb is that the engine takes in 1 gram/second at idle for every litre of engine displacement.
And I’m still used to older, larger engines, so the fact that it was around 1-2 g/s was quite alarming, and enough to confirm my diagnosis. It’s got a vacuum leak.*
Indeed, it did. Because the engine is turbocharged, it’s got a complicated PCV system on it, mostly built into the valve cover, and that had a rather substantial leak in it. I could hear it sucking in outside air--air which never went by the MAF, and therefore never entered into any of the PCM’s calculations. I could stick my finger over it, the sucking stopped, and the idle smoothed out.
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*1-2 g/s is actually theoretically possible on this little 1.4L, so my alarm was somewhat misplaced, but as they say, even a blind squirrel finds a nut once and a while.
A new valve cover fixed her right up, and down the road went another happy customer.
I could leave y’all with just that one, but this next one is much quicker, and applies what we’ve learned in this blog post.
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This is the easy way to get at the oxygen sensors on one of these
There are times as a tech when you already know it’s going to be bad news for the customer, and this was one of those times.
The Jeep came in with a check engine light and it seemed to run okay. So I pulled codes, and this is what I got:
P0057
P0037
P0051
P0031
Now, you may have noticed a bit of symmetry to these. A council of wizards engineers came up with the code numbering system and they’re basically assigned in blocks (casting your mind back to the Cruze, you’ll remember that the idles too high and idles too low code were very similar numbers).
This one is a V-engine, so it’s got a bank 1 (the side that cylinder #1 is in) and a bank 2 (the other side*)
The codes are, in order,
Oxygen Heater Circuit 2/2
Oxygen Heater Circuit 1/2
Oxygen Heater Circuit 2/1
Oxygen Heater Circuit 1/1
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*Before you think that’s a stupid way of numbering things, rail cars have an A and a B end. The B end is the end with the brake wheel, the A end is the other end. So there’s a tradition of that kind of nomenclature.
Oxygen sensors don’t work unless they’re hot. Back in Ye Olde Times, the fact that they were in the exhaust served well enough to heat them up, and once they got warm, the engine went into fuel control.
In modern times, we care more about emissions and fuel economy, so waiting five minutes or ten minutes or literally forever if you’re in Anchorage in the winter time was not a good thing, so oxygen sensors got little toasters built right into them. Those turn on and get the sensors working right away, and they are generally quite quick.
Something’s got to turn them on, and that duty falls to the PCM, who decides based on all its inputs how much to run them. Since a toaster is basically a short in a wire, run ‘em for too long, and the driver on the PCM melts.
I cleared the codes and they came back basically instantly on the next key cycle. That’s always nice for diagnosis; that means it’s a hard fault.
While it’s possible that each sensor failed individually, it’s more likely that there’s a common cause, so the first thing to do is consult Ye Olde Wiring Diagrams and see what they all have in common.
There are four separate power wires, and four separate ground wires. So it can’t be a simple broken wire--it would have to be four broken wires. Not impossible, but unlikely, especially since there aren’t any other faults.
There is not a dedicated fuse for the oxygen sensor heaters, because Chrysler wanted to live dangerously. That means that they have exactly two components in common: Ground 104 (all the wires go there), and the PCM.
It wasn’t Ground 104.
My manager wouldn’t let me take the PCM out and pull the cover off, which is a shame. There’s nothing I like better than confirming a diagnosis by seeing the melted or exploded circuit inside the PCM. They usually look like this:
Yes, you get that image again. I googled it, and that was one of the top results. Apparently, nobody’s taking pictures of the insides of failed PCMs except me.
Stay tuned for further adventures in mechanicing! One of these days I’m actually going to blog about the bizarre electrical problem on the Sprinter, and when I’m in a ragey mood, I’ll tell you all about pulling the front cover off a 5.3L “just to see if the engine out of time.” Protip, there are tools--WHICH WE HAVE AT OUR SHOP--that can determine that without doing an eight-hour teardown. Spoiler, it wasn’t out of time.
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Obligatory batpony picture
I vaguely remember a story with an airplane that got a failure in the diagnostic system wich resulted in all the fuel being dropped in the ocean for safety. The pilot managed to keep the plane going with some wind power generator and landed succesfully in the Azores.
I also recall that at some point my father piloted a project for the government agency he work for, they implemented the "arbre des cause" (tree of causes) system. Basically you take the result and say what caused it, what caused that cause till you find the root problem.
"Any Mazda rotary fans..." I had a '76 (or so??) Mazda RX-4 with a rotary. Sucked gas like a straw because it really needed the (whatever rotarys have for seals) replaced. Step down on the gas hard, it would try to stall out, then accelerate like a racehorse, and the accumulated gasoline in the exhaust manifold would detonate with a loud "BANG!" We left a stop light once, my wife looked in the rear view mirror and said, "The guy behind us pulled over and is looking under his car to see what blew up." Serious and honest to God, we had the spark plug wires backwards on it for the first half of the time we owned it. We put them on the right way and I couldn't tell the difference. It always started, it always ran, it rusted like an old tin can and I wound up selling it for $100 to a friend because it needed... everything from brakes to struts.
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That sounds familiar. I think it was a Canadian flight... either a 737 or a 767 if I'm remembering correctly.
(There was an episode on it in this excellent docudrama series named either Mayday (original Canadian title and current U.S. title) or Air Crash Investigation (elsewhere in the world). Stylistically, the show's sort of a blend of CSI and a disaster documentary and has been nominated for various awards.)
Also, the "wind power generator" you're thinking of would be the RAT (Ram Air Turbine).
Multiple failures...
I am reminded of QANTAS flight 32 from Singapore. An Airbus A380 that had an engine explode after takeoff. It took out most of the wiring harnesses in the wing, hydraulic lines and fuel lines. They actually broke records for how many failures their ECAM system reported.
Airbus invented a new term for the dread pilots get when the system keeps reporting new things wrong with the plane; ECAM fatigue. The courtroom reviewing the incident demanded the alarms be shut off after about two minutes, the pilots on the flight had to suffer through them for nearly two hours.
They got the plane down safely, with no injuries reported. The book about the incident is a fascinating read. QF32 for those interested in tracking it down.
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It was a canadian fligth, from the Québécois transporter Air Transat I think.
As for the RAT, well, I work with bicycle, so I'm not all that familiar with the technicalities of a plane I afraid.
But thanks, always fun to learn new thing!
Well, most modern cars, yeah. I still see an older car from time to time (as I'm sure you do) wherein the PCM thinks everything is perfectly fine, it just happens to be in Antarctica. Ah, programmers. Can't believe it took them like 20 years to figure out that there should be a little check in the code for whether or not a temp sensor is reading, well, basically open.
Was it one of those fucking German style diaphragm thingies? Who'd've thought that a paper-thin piece of rubber would just fucking rip after being worked back and forth for a couple years? God, I change so many of those.
Eh, it was probably one of those Chrysler PCMs that's filled with jello, anyway.
Also I feel like you blogged about the Sprinter and the 5.3 already... unless you told me those in person and I'm having a brain fart.
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No worries. I just found calling it "The Rat" so memorable that I'd never forget it even if my brain weren't optimized for trivia.
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Now that one I definitely remember, because it was one of my two favourite Mayday episodes. (The other being British Airways Flight 9... but don't look that up if you're unfamiliar with it and might want to track down the corresponding episode. Following along with the mystery of what had gone wrong was a big part of what made it so memorable the first time through.)
All these fancy tools to pull codes with, and more often than not when something's wrong with my car I pull the codes with the ignition key and the check engine light, then look the numbers up in a table to see what they mean. (And if that doesn't help, *then* bother the friend with a proper code reader.)
Although what's really fun is the constant CEL because the ECU from the 2.7l that *used* to be in the car can't see some steering pump position sensor that the current 3.2l engine doesn't even have a harness connector for, let alone said sensor switch. Sometime I really need to look up what pins on the ECU that goes to so that I can jumper them to keep that fault code cleared... (There are, uh, "reasons" for that ECU/engine mismatch, though the main one involves the sentry keys that weren't offered with the 2.7l and that the car isn't wired for. Maybe if I knew what ECU pins to use to wire the key chip sensor coil directly to the ECU with (and then tape the matching key top to the sensor coil) rather than having to fool about with the column... But that's a tale for another day, I suspect.)
This is even more fun when you don't have error codes. Fortunately if you're doing something like that you typically have more tools and techniques available.
I actually have done this a decent amount. three is good enough for back of the envelope calculations. I've also done this in low level code where sometimes you need an integer or the cpu can't do decimals in hardware.
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It wasn't the Gimli Glider. That plane was under fueled.
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I know. The Gimli Glider was also covered in a different episode, but both were Canadian airlines. That said, I was wrong about the type of aircraft. The one that landed in the Azores was an Airbus A330-200.
Source: https://en.wikipedia.org/wiki/List_of_Mayday_episodes
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Before Mayday/Air Crash Investigations episodes and Seconds From Disaster episodes got copyright-purged from youtube (they're still mostly on dailymotion), I used to queue up a playlist while on the treadmill at the gym. The sheer number of things that can go wrong with planes and trains and stuff is mind-boggling and it's a wonder anyone is willing to get in one of those tin cans of death.
The most impressive thing about the Gimli Glider is that crazy SOB pulled a slip in a 767 to kill speed on final approach.
studyflight.com/wp-content/uploads/2017/08/slip4.jpg
I always love reading Detective Admiral Biscuit and the Case of the wronged Car
i.kym-cdn.com/photos/images/newsfeed/000/505/048/af5.gif
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You have all selected great examples of Aviation Under Pressure Done Right.
The Gimli incident was a classic case of the right people, in the right place, at the right time. The Captain was a hobby glider pilot who had the balls to do what logically needed to be done regardless of how insane it seemed (actually sideslipping a new 767) and the co-pilot was an ex Air Force pilot who used to fly out of Gimli so he knew it was there to be used.
QF32 was a case of having a few experienced blokes who had the right training and were able to sort the essential info from the reams of errors the computers were throwing at them, a bit like Admiral Biscuit and his Cruze... who cares if the taillight circuit is faulty if the engine won't run? They remembered the golden rule, 'Fly The Plane' because the rest is pointless if you forget to do that. The Captain was cut from the same mould as the Captain of BA Speedbird 9 in that he had that very calm and understated way of announcing things to the passengers and in the press briefings later.
BA Speedbird 9 was again calm and clear minds, and determination, combined with engines that survived initially being filled with volcanic ash which melted into glass and then being able to eject enough of the glass when it cracked as it cooled to allow them to restart... and to then survive going through that again a second time when the plane regained altitude and ended up in the ash cloud again. If I remember the Captain's announcement it was something like "Ladies and gentlemen, this is your captain speaking. We have had a small problem. All four engines have stopped. Of course, we are doing our damnedest to get them going again. I trust you are not in too much distress while we sort this out."
Reeve 8 was a crew who, as Admiral mentioned, rather than focussing on what they didn't have, focussed on what they did have and then worked out how to make that enough to land the plane and also having the cojones to do a missed approach rather than succumb to 'get-there-itis' at the last minute.
Like the other folks here, always happy to read another tale of Admiral Biscuit and his Adventures in the World of Automotive Quirks.
So was this actually a cracked valve cover or a component in the valve cover? If a cracked cover, do you get cracked valve covers that often? I've only ever seen one from either accident damage or incompetent fitting. Either way, I love how the computer has thrown 9 errors and only one P1101-00 Intake Air Flow System Performance is even vaguely descriptive of the final issue. Side note, did you get to diagnose and fix the power steering programming error?
Seems perfectly logical to me...
Why not? If it is scrap then why not do a post-mortem... or did the Jeep leave the shop with a faulty PCM still in situ?
I have seen a few failures like this snowball as the fault is actually one of the downstream units and, while swapping the module with the driver fixes it, the replaced module eventually dies again sometime after. A few years back I had a customer ask us to asssist in a situation where a radio system had had its master controller replaced four (yes, four times) previously in the last few months by their contracted maintenance company and it had just gone belly-up again. As I was onsite at the time for a different system which we maintained, they had asked me to look into it as the usual mob were going to be delayed and they wanted to get things moving again (remote mining site and downtime is big money there). Of course, armed with the info that this was now the fifth controller to go kablewie, like you, I did a post-mortem on the in place one and found evidence of major current overdraw on a one section of the mainboard and after a bit of wiring tracing later I found a sub module that had heat stressed wiring and signs of internal overheating. Make a new cable set, replace sub module with an on site spare, replace MOSFETs on mainboard and do some creative PCB track repairs (no spare main controller but there was another spare sub-unit that used the same model MOSFETs that I could raid) and, lo and behold, site is online again. Each time I am there the the radio tech likes to remind me that my 'bodge' repair is still going strong even though I told him at the time that they should still look at getting their contractors to replace the master in the near future as I could not make any guarantees on my hack and patch repairs. Strangely, they changed maintenance contractors just after that...
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If you actually look at the numbers, the odds are much higher that you'll die from something you don't give a second thought to, like a car accident.
That's the human brain's fixation on spectacular threats over mundane threats for you.
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As do I.
He is the mechanic we all wish we had.
Hey Biscuit! I have a 2015 Volvo S60. Have you ever worked on one of Volvo's Drive-E engines? If so, what do you think of them?
Does that dark light on your reactor control panel mean:
Or, maybe, they put the warning light on the back of the panel, and nobody sits on that side of the console on the night shift?
As riviting as all that technical computer jargon is, i think ill stick with my ye olde quadrajets and other assorted things of ancient, bygone eras... but i do like learning new things. Though, in hindsight, my mercedes buddy will still likely wipe the floor with me in terms of new knowledge.
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That’s important for pretty much everything that you have to diagnose, including sick people, because if you only treat the symptom you don’t actually fix anything.
My line of work, once we find the failed part in most cases we don’t investigate further, but sometimes it is important . . . as on the Jeep, drivers rarely melt on their own; something caused that, and if we don’t fix the root cause, pretty soon the new PCM is going to have the same problem the old one did.
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I blew the muffler off my Chevy truck in a similar manner. The echo was quite impressive.
I had an old S-10 like that. No matter what kind of mechanical repair I made, it didn’t get better. Parts fell off it that have never fallen off anything else I’ve owned, ever. Like the fuel pump (block-mounted), and the driver’s side door latch. Left a trail of oil wherever it went, too.
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Multiple failures...
That’s the kind of record you don’t want to set. Probably the ECAM could have just reported that the left wing was still on the airplane, but nothing on it worked (because IIRC, that was essentially the case).
That’s always the fine line with alarms and warning lights and suchlike. They need to be on long enough so that the operators know something’s gone wrong, but not so long that the operators can’t diagnose the machine due to distractions.
The episode of Mayday/Air Crash Investigation was really good, too.
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I’ve watched most of the episodes, at least when I can find them online.
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We both know it’s true.
Oh, yeah, every now and then. Not as much any more, since OBD-II cars are now more than 20 years old, and they’re mostly smart enough to ignore an open CTS. They should have done like they did with TPS, and had the base value not be zero, so the computer would know if it was less than say .5 volt it should be ignored.
That’s why Chrysler has biased their O2 sensors for years, so the computer knows if it’s open.
Yes, it was, and the worst part is that it wasn’t the original valve cover; we’d already replaced it (with a new GM unit) about sixteen months ago.
Given how the kid drives the car, maybe it’s not surprising that it failed again.
But it could have been jello with a scorched crater in it, which would have been cool.
I’m sure I told you in person about the 5.3--I haven’t blogged about that one specifically, I don’t think. Would have had to be in July, if I had. I’ve mentioned the Sprinter a time or two, but never actually done a blog post about it, even though I’ve got a video of the malfunction in action (which was really cool).
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That works very well on a lot of older cars (and in fact on many, like GM OBD-I, that’s how you were supposed to do it). Volvo used to have a diagnostic patchboard built into the car to be used in that manner. Most new cars won’t flash codes, or won’t flash all codes.
Depending on the car’s logic, you may or may not be able to jumper the pins to fool the PCM. Newer cars are smarter about that. I don’t know off the top of my head how Chrysler’s security system worked, so I don’t know how easy it is to fool. Older GMs, you just needed to put a resistor in the wire, and it’d think that every key was the right key. Ford’s got a little RFID pill that you could presumably tape to the halo (which you could mount anywhere) and it would be happy with that. You can even get the pills out of aftermarket keys and some OE keys.
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We’ve got more limited options sometimes, since there isn’t much documentation on the software end of things. Diagnosed a Honda a while back that couldn’t communicate with some modules but could with others; however, according to the wiring diagram, it shouldn’t have been able to. Grr.
Yeah, it’s probably plenty close enough for lots of things, but obviously not when you need an exact number.
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Hey, there’s nothing wrong with the “it works in a small aircraft and a fighter jet, so why wouldn’t it also work in a 767?” Probably the owner’s manual for the airplane says to never do that.
And speaking of “never do that,” what about FedEx flight 705? Some of the things that pilot did would make a fighter pilot cry, and he did it with a fully-loaded DC-10.
4916571
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derpicdn.net/img/view/2013/3/29/282201__safe_fluttershy_angry_animated_clothes_hoodie_horse+problems_ipad_source+filmmaker.gif
4916648
It’s a diaphragm on the valve cover that’s part of the PCV system.
i.ytimg.com/vi/SFzFMYu4blE/maxresdefault.jpg
This guy’s got the glued-on cover chipped off, so you can see the diaphragm.
The guy left without fixing it. If he does bring it back and we put a PCM in it, I’ll look inside if I can get the cover off (PCMs usually have core charges, and the dealer isn’t too happy when the cover’s been broken off--they won’t give you the core charge back).
The two main takeaways are that good documentation is important--if you keep having to change the same part*, there’s probably something causing the failure. Also, sometimes totally cobbled-together repairs last a long time. I stripped out a hole in the frame of my glasses, and fixed it with a little twist of copper wire, ‘cause that’s what I had lying around. I think that repair lasted for five or six years, until I finally got new glasses.
*There was a NTSB report on a ship fire, where it turned out that they’d had to replace one of the injector pipes for leaking something like seven times before the engine caught fire. The root cause was they didn’t put an anti-vibration clamp back on when they replaced the first pipe, and then all the others cracked due to excessive vibration.
4916705
Don’t ever let me do body work, though.
i.imgur.com/yo4Hop7.jpg
4916713
Never even heard of them until just now.
Volvos are pretty good cars, from what I know, but we don’t work on them. None of our customers own one.
4916845
I can’t remember the airline, but back in the 70s or early 80s, a widebody jet crashed in the Everglades because the landing gear indicator bulb had burned out, and the entire crew was busy diagnosing that instead of actually flying the airplane.
Most warning lights on cars have to prove out when the key’s turned on (the bulb lights up for a few seconds). That doesn’t totally eliminate the possibility of the bulb failing on the drive, but it does lessen the chance.
If it’s a really critical system on a car, a burned-out light bulb can disable it. Some GM products, the cruise control won’t work if there’s a brake light bulb out.
I’m actually happy that cars can now punish the driver for ignoring certain requirements.
But to your main point, having a control panel of any type badly designed is just asking for trouble in the future.
4916930
Heh, you’re welcome to your quadrajets. I’d rather have fuel injection and modern engine controls then that old mechanical stuff. Maybe if I was working on cars as a hobby, I’d enjoy the older stuff more.
It's as if the comment you left on my story came true. Or maybe this had already happened when you made that one. Still, I had no idea when I wrote that story, so I find the coincidence amusing nonetheless.
4916996
I thought I’d mentioned the different types of codes somewhere but couldn’t remember where. Thanks!
And no, both of these cars were from yesterday (Tuesday)--it was all fresh, new stuff.
Still waiting on the pony mechanic or maybe a pony comes to earth and works in a mechanics shop.
4917047
Did you say the pony mechanic?
Solo
Drive
Highway 502
Gotcha covered!
4916994
Yeah, i see where you are coming from. I enjoy tinkering on the old stuff, seems simpler to me. Though, the new gen stuff does have its place. Certainly more comfortable driving my 09 half ton chevy long distances then it it driving the ol '70 gmc 3/4 ton. haha
4916988
Dig the Frankenstein look on that car, is it it's Halloween costume?
4916970
yeah, that's pretty annoying, bad documentation sucks. Today I was working with a fan where the datasheet had wrong info. If you set up the circuit the way the datasheet says, it won't work.
... That's an interesting design.
It's 95% of the correct value. So not atrocious, but still not the norm. Especially with modern calculators.
4917101
It’s simpler in a different way. It’s all mechanical, so if you’re good with that, it’s easier. If you’re good with electronics, though, it’s unnecessarily complicated (such as a distributor with centrifugal advance and vacuum advance along with delay valves and thermal valves, like my old S-10 had). Plus, of course, mechanical systems aren’t very good at adapting to changing operating conditions, nor are they particularly good at self-diagnosis.
4917174
Heh, no, that was the repair I made for the rest of its life (as it turned out). Rather than spend a few bucks on a new front bumper after a deer hit. . . .
4917441
We also get either misleading or flat-out wrong documentation more often than we should. Even from the manufacturer (although that’s fortunately less common than from aftermarket sources).
The short version is that a lot of cars use multiple networks, which sometimes communicate on different pins on the diagnostic link, and other times the messages are translated by a gateway module. If there was a pass-through though (which there must have been), the wiring diagram didn’t show it.
There’s a lot of stuff I ballpark, but then I’m not a proper engineer, so I can get away with it.
4917534
Very true. Though i do believe there was a jaguar that had carbs that could adjust for differences in altitude. quite neat.
4916990
Hmm...
Will have to introduce you to Elizabeth when the next Bronycon rolls around.
4917539
I never get how people can let stuff like that out. i get that typos and mistakes happen, but i've seen some really bad documents. My favorite is a drawing (that I couldn't enlarge or download) that used neon blue and yellow.
I never really understood why vehicle networks are arranged the way they are. To me they seem really disorganized unplanned
honestly you'd be surprised at the amount of assumptions we make. They're different than the types you use, but we make a ton. Pi has a button on the calculator (and a lot of software has the same) so it's really easy just to use the maximum precision for that