Mechanic: Denali II: Denali Harder Ft the Cruze! · 1:50am Apr 10th, 2019
Not the sad Cruze you’re thinking of. That one’s dead, and it stayed dead.
We’re also gonna see that Denali again, and finally solve the mystery of where the Personal Audio Link Control Module went. Plus, we’ll have some fun asides, so
Man, y’all are on this!
Not all that long ago, got a Cruze towed in. No start.
So I mosey out to the parking lot, jump box in hand, just to see what’s what with this thing.
Naturally, it starts right away. On the one hand, that’s a plus, because I don’t have to push it in. On the other hand, I don’t know was was wrong with it. Could have been anything from a customer who tried to start it with the wrong key, one which would turn in the ignition but had the wrong security code (you laugh, but that happened to one of our customers), to a weak battery or maybe a loose battery cable. Might be a starter that’s on the cusp of failure, or heck, could even be a network problem.
Some of you--most of you--who read the last blog post are probably thinking that the low-speed network might have failed, and the cleverest of you might even be thinking that it was a Side Object Detection Module which caused the failure.
Those of you who are thinking that are absolutely correct, and me giving you this spoiler right away is going to save me a lot of explaining time.
I didn’t bother to save the codes this time for y’all. It’d be fair to say that they’re essentially the same as the ones on the Denali. Pretty much all the modules on the low speed network couldn’t be found when they were looked for, and there were the appropriate code in the module who did the looking.
I didn’t know this right away. After all, I’m coming to you after the fact; I didn’t have the benefit of the narrator telling me it was the same thing again.
But I did have the benefit of learning from the Denali, and not repeating the mistakes I’d made on that one.
So this car, I put on the hoist right away, and I also grabbed the GM scan tool for its wonderful all-module diagnostic list (you remember that one from last time). Here’s what I got:
And since I now knew that the Side Object Detection Modules could fail and take down the network, I started with a physical examination.
This time, I saw what I wanted to see. There was corrosion inside the connector for the Left Side Object Detection Module, and corrosion inside a connector can lead to numerous derangements of electrical equipment.*
That was enough to condemn the module, and since it had set codes for the other one, too, it was wise to replace it as a precaution. As you’ll remember from the Denali, the Right Side Object Detection Module talks to the left first before going on the network, and there was no way of isolating it from the failure on the other side of the car. Any tests we could make at that point would be inconclusive.
The wiring harness on the rear bumper would also have to be replaced, due to the corrosion.
_______________________________
*
Loose electrical connections or mechanical fastenings have caused numerous derangements of electrical equipment
--NTSB, Fire On Board the Small Passenger Vessel Port Imperial Manhattan, MAR-02/02
This could just be a blog post about how I learned from wasting a lot of time chasing my own tail--and that’s a lesson we all hopefully learn before doing it a second time--but there’s more to it than that.
Remember, we still don’t know where the Personal Audio Link Control Module went.
And as strange as it seems, the Cruze has the answer.
In America, we have options when we order cars. Generally, there’s a base model option, which is the cheapest. And then there are various add-on packages. Some of the options can be ordered individually, and others come as part of a trimline. To give an older example, my dad once bought a Chevy Venture Value Van. The choice you got was if you wanted it to be blue, white, or red. That was it.
On the other end of that was the Oldsmobile Silhouette Warner Brother’s Edition. Leather, alloy wheels, DVD player for the kids, rear heat, rear AC, etc. Equipment that was added on for that particular trimline.
And in the middle, there were plenty of vans with alloy wheels but not leather, or steel wheels but with rear heat. If you want to get an idea of how all this works, you can go to any manufacturer’s website and browse around.
The point is that some vehicles have lots of bells and whistles and some of them don’t.
Back in Ye Olden Days, if you wanted an option, it was a simple matter of adding a wire here and there, maybe a toggle switch, mount a spoiler to the trunk, and so on.
Nowadays, a lot of that stuff is controlled by computers, and the computers obviously have to know what the car’s got that they can control.
There are various ways of doing this. In some cases, specific modules have to be configured to know which equipment they have. For example, if a body control module is replaced, it might need to be told if the car has power windows or not. A FCIM (Mopar-speak for Forward Control Interface Module . . . a smart fuse box) might want to know if there are fog lights or not.
Some modules you can just toss on the network and they’ll do their own thing. Sometimes overhead consoles just pull data off the line and don’t do anything else. Others you’ve got to tell the appropriate computer that it’s there.
Of course, when it comes from the factory, the car knows what it’s got. It knows its as-built configuration. The Cruze knew, for example, that it had Side Object Detection Modules, which distinguished it from all the Cruzes that don’t.
Someday, I might get into RPO codes, but today is not that day.
Cast your mind aside from the world of GM for a moment, and picture a Ford. A white Ford F250 pickup truck, one of the last of the squarebodies. It’s got a network of sorts, but it’s a dumb network, all things considered. Only a few modules, really. Three or four, or maybe if it’s really well-equipped, it might have six or seven. Like, we’re talking a King Ranch, but before those were actually a thing.
The Ford scan tool also has a network diagnostic function. In all honestly, I’d imagine that every decent OE scan tool does these days.
Just like GM, it polls all the modules, and sees who’s talking, who’s got codes, and so forth.
But Ford went one step further.
They didn’t make their interface prettier; in fact, it’s very much late 90s Internet, albeit without dancing hamsters. But one thing it does have is two discrete sections. One of them is just modules.
PCM. ABS. IPC. GEM.
And then it’s got a second section, optional modules. PATS, PAM, etc. The modules that the truck might have been equipped with, but it might not have. If one of those modules doesn’t communicate, well, maybe the truck just doesn’t have that module. The tech should find out before attempting to diagnose it.
I believe--to cover the also-ran American automaker--that Daimler Fiat Chrysler has accurate build info when you hook up to any given car, and it greys out the modules that that car doesn’t have, and uses a different color to indicate modules that ought to be there but which it can’t communicate with. Never used it, so I don’t know for sure.
As some of you might have guessed, GM didn’t think of this.
Most of the vehicle data is automatically populated when the GM tool is hooked up to a car. It pulls the VIN, then it uses the interwebz to talk to a centrally-located GM data center, which hopefully knows how that particular vehicle was configured from the factory. It knows what engine the car has, what transmission, etc. Most of the major options, it knows.
The Cruze was not communicating with its Steering Lock Control Module.
The central GM computer knew that the Cruze did not have a Steering Lock Control Module. It said so right on the limited build section for the car (which I really should have taken a picture of, but I didn’t).
While I didn’t go searching for it, I would imagine that the Cruze also did not have a Trailer Interface Control Module. I’d expect that only ones equipped from the factory with trailer hitches do.
Which of course explains the lack of communication. A module that doesn’t exist on that particular car can’t very well communicate, now can it?
This lead me to the epiphany that the Denali’s Personal Audio Link Control Module was also not equipped. That was why it didn’t show up on any wiring diagrams for the vehicle. Could be that no Denalis have them, and that’s only on Buick Enclaves, which they share a platform with.
It’s also entirely possible that if I went back through all the various codes that the modules had set on the Denali, there would be none for the Personal Audio Link Control Module, since all of those modules knew it wasn’t there, so they’d have no reason to try and talk with it.
Certainly, while the Cruze’s scan tool data showed a missing Trailer and Steering Lock module, none of the computers reported that, since they knew to not look for it.
Before I forget, here’s a picture of the rear bumper cover, off the vehicle. The black boxes on the left and right are the Side Object Detection Modules, and the four sensors across the middle are the park aid sensors.
This, right here, would be a good place to end the blog. I learned a very important friendship lesson, and while it might have taken me a day to bumble into a solution for the Denali, I got it figured out on the Cruze in less than an hour.
But we’re not stopping yet!
Not overly long after the Cruze went on its happy way, the Denali got towed back in.
For a no start.
Again.
My manager was off that day. We only had my manger’s kid and our new mechanic. [Who informed me today that in further blog posts, he wants to be called Earwig.]
“I got an idea,” I said. “I think I know what’s wrong with the Denali. I just gotta get up under her rear bumper and give her a little tickle.”
Neither the manager’s kid nor Earwig had the slightest idea what I was going on about, of course.
I slid under it out in the parking lot. It was raining, which was unfortunate, and of course all the mud and possibly also horse leavings that I’d washed off of it were back again. And it still wasn’t overly comfortable to work around the tight space between the muffler and bumper cover, but I got it, and lo and behold, she fired right up. The Left Side Object Detection Module had also failed.
We verified that when it was in the shop; with a little bit more working room, I was able to plug it in and unplug it and watch it take down the network practically every time it went online.
The customer really needed it back, so I left the module unplugged--to save the rest of the network--and let her take it for the weekend, and it didn’t malfunction at all. A couple days later, I put a new one in, and the vehicle was happy again.
So in short, my diagnosis time went from five or six hours, to about one hour, to maybe five minutes lying on my back in the parking lot.
This is what blue car theory is all about.
Sure, it isn’t always right, but instead of following the flowcharts that GM provides for intermittent no-starts, I went right to something that I’ve learned is a probable cause. Had I been wrong, I then would have gone through the normal diagnostic procedure . . . but I’d learned that the Side Object Detection Modules weren’t as waterproof as GM hoped, and when they got corrosion inside, they could wreak havoc on the network.
Just ‘cause y’all are interested, we pried one of them apart. They’re not meant to come apart, but they’re only plastic, and when you’re not intending to put something back together again, it’s a lot easier to disassemble it. Plus, we had four of them, so if we messed up taking one apart, we’d learn for the next one.
Unsurprisingly, things didn’t look too good inside.
As Adam Savage would say, “Well, there’s your problem.”
I wonder if the $0.05 per module cost savings on a crappy gasket will surpass the warranty outlay. 🤔
"Most of the vehicle data is automatically populated when the GM tool is hooked up to a car. It pulls the VIN, then it uses the interwebz to talk to a centrally-located GM data center, which hopefully knows how that particular vehicle was configured from the factory. It knows what engine the car has, what transmission..."
Hopefully also "...if it has been reported stolen so it can notify the police along with the address of the shop..."
HP has a function like that on (ahem) certain of our computer hardware. If it connects to the internet, it calls home. If it is marked in HP's database as stolen, interesting things start to happen, certain Federal agencies get notified, calls happen, etc... (Yes, even if the drive has been totally wiped and reloaded with something else)
5041892
Or they could have just potted the stupid thing (covered it in resin), not bothered with the back cover and it would never have moisture problems.
Happy vehiculars, yay!
It ain't as bad as the 1970s. That decade, Detroit recalled more cars than it sold.
So did VW (but a lot of it was upgrading stuff)
For example, in the 1950s, they didn't have a gas gage.
Recommended kluge to fix it. Drop a handful of extra large marbles into the tank
You hear them rattling around, buy more gas.
They also left out the windshield wiper motor. The wipers ran off the compressed air in the spare tire
They don't build them like that anymore -thank God
Lately we've been dealing with a VW Passat with a wet transmission computer. Exceedingly common problem on those cars, as they have a very nasty habit of collecting leaves in the battery area / wiper tub, and that area fills with rain water until it overflows into the fresh air intake and floods the passenger's floor pan... which is where the brilliant German engineers thought to put the trans computer, under the carpet. Good thing to remember if you ever happen upon a Passat or A6 with trans problems. I had one many years ago in the middle of winter and I opened the computer and the circuit board had become a large ice cube. We sold that car to a friend, he's still got it.
This one was a bit of a challenge because it had a very minor transmission code, operated normally otherwise, and was in the shop for unrelated problems. In fact, the FIRST thing I did to this care before I even knew it had a trans problem, was to take out the battery, and make sure the tub was clear of leaves, and to remove those stupid rubber grommet water-drain type things, that let water drain out, but trap leaves. Funny enough, those rubber things were gone already, and the area was totally clean. Hmmm...
5041892 The thing about gaskets on electronics, is that they tend to fail anyway. Water finds its way in, one way or another. The best thing to do is either to pot the whole PCB, or to design the case to shed water. For example, the computer's box could be a box that is one solid plastic box, with no bottom. And the PCB would slide up into the bottom, with any connectors also at the bottom. Gravity would keep water out of it forever... unless it was in a flood, but in that case, you'd have bigger problems than a wet computer.
At first I thought you'd taken a picture of like a discount grocery store attempt at making a circuit board layer cake, but the cake decorator was drunk, hungover, or possibly high while trying to make it.
...then I realised that was all corrosion and I had a moment. Mother of god, that's... a problem.
5041959
I can't tell if you're your joking or not.
Please tell me you're joking.
5041985
https://www.goliath.com/auto/the-10-most-infamous-car-recalls-in-history/
https://www.anythingaboutcars.com/1970s-cars.html
If you're talking about the VW stuff, that's stuff that I recall from my youth, 50+ years ago
When owning a VW Beetle was considered weird
However bad they are today, they were worse 40-50 years ago
I died a little inside when I saw that corroded circuit board. Good stuff.
Compare that with my local holden car dealership's work around replacing my death-inducing airbag problem:
1. Buy car.
2. Realise that car might have a death-inducing airbag (airbag goes off, kills person with kindness. and metal shrapnel)
3. Talk to people when I take it in - they up-front told me that my airbag was like that, but so was the past x years worth of cars, and they'll replace it asap when they can
4. Send me a letter with lots of "your airbag could kill you with kindness. also lots of metal. this is bad. let us replace it for you asap" text
5. I call them, they order the part and let me know they'll call in the next two weeks
6. Call a week later to tell me my car is booked in the next day
7. Car goes in. Airbag will no longer kill me with metal shrapnel, or kindness.
That circuit board looks like it was fed to salted roads for a few winters.
Had a PAIR of interesting recalls when I worked for Toyota. Camry steering wheel retaining nut torque. The steering wheels on some Camrys would actually feel a wiggly kind of loose. As in: The retaining nut had nearly backed off. Yeah. Forget the 35 ft-lbs. Break out the biggest 1/2 inch ratchet/breaker bar you've got, unplug the horn, remove the airbag module, tighten the everloving **** out of the steering wheel nut, reassemble, done.
TWO separate recalls. The second one added more cars (more years) and increased the torque value.
If there was ever a case for potting a board, this is it. Seriously, that board being placed in a plastic box right behind the rear wheels is just plain sad. At least it will make a nice show piece for when the customer asks "So what was the problem?"
5042037
You ever service a smoker's PC?
5041892
Since I don’t work at a dealership, I can’t say, but I bet they tend to last through the warranty period. I’d bet that that’s the kind of thing that is only covered by the 3/36 warranty, and after that, the customer pays.
5041895
I don’t know if they’re doing that yet.
They could, and they could also remotely disable it (for GM with OnStar), but I don’t know if they do. That’s a can of worms right there, and I don’t know if the automakers really want to get involved with that unless they’re legally required to do so.
Huh, that’s interesting to know. And I thought my manager was being paranoid with the computer telling the government what it was doing. (granted, the way he thought it worked was pure tinfoil hat stuff)
5041927
I don’t know if they could have potted it, honestly. Not an electronics designer, mind, but it sends and receives a signal (sonar/radar) and I think that the traces at either end of the board are the antennas, and I don’t know if they’d work if they were covered in potting compound.
5041943
Well, happy now. Hopefully they stay happy.
5041959
Recent times haven’t all been great for automakers, either. Early 2000s, Ford had a massive recall on Explorers, and also on practically every Ford with a brake switch on the master cylinder. GM had the ignition switch recall, Jeep had the fuel tank recall, VW had the diesel emissions issues, and Toyota had a recall on Tacoma frames. I just recently got to do some front end work on a Tacoma that had just been re-framed.
5041962
They’re not alone in that; my Regal lost its airbag computer due to interior flooding (minor, but enough to drown the SDM), and I recently found out that Outback PCMs are on the firewall just below the blower motor. And I did a blower motor on a Ford Edge (IIRC) somewhat recently that had clearly been ingesting water but the customer apparently wasn’t interested in finding out why (or else my manager didn’t bother to tell them, which is the more likely possibility).
None of our customers currently own either of those things, and that makes me happy.
In some ways, that would help with keeping the computer cool. In all other ways, that’s a problem.
We once froze a Chrysler PCM for diagnosis . . . basically, proving that the drivers went bad when the computer got hot.
There are a few drains that never worked as intended. The screens in vortec distributers as I recall tended to let moisture in but not back out and some techs avoided comebacks by just knocking them out of the distributor. There are also always problems with putting important wires under the battery, since if the battery leaks, the wires usually don’t like that. Also putting things under windshield washer bottles--I’ve seen that cause problems before.
One of the coolest failures I ever saw of a PCM was on an Express van, where the PCM was under the master cylinder. Said master cylinder had been leaking, and had eaten through the PCM case.
Then the radiator started to leak, and it filled the PCM with coolant. Surprisingly, the PCM still worked well enough for the van to run, but it wasn’t very happy about it.
Back in the late 60s, my grandpa worked for Fisher Body. He was working on the Nova (of the era where the stamped frame rails would rust out from the inside and cause the cradle to fall out when the car was lifted) and pointed out that they needed to include drain holes to let the water out.
He got outvoted, since they were going to design those frame rails “so water couldn’t get it.” But of course water could get in; water always gets in.
5041976
Interestingly, the person or people who designed this module might have been drunk, hungover, or high while designing it.
Amusingly enough, it’s not the worst computer I’ve seen inside of. I really need to take more pictures of that type of thing.
I really wish I’d gotten a picture of the Nissan computer that had a driver failure so bad you could see the burn mark on the outside of the case. Made diagnosis easy, though.
5041994
To be fair to the side saddle fuel tank, it was an improvement over having the fuel tank inside the cab, behind the seat, as the prior generation of truck had had.
They also had a field warning that radiator fan blades could fly off, and given the condition of the one I owned, I figured basically anything could fly off at any moment.
They did offer $500 additional trade-in value per truck, but I never owned enough of those trucks at any one time to leverage it into a free car.
5042037
What always amazes me about that kind of thing is if the customer was correct about when the vehicle failed, that circuit board was working properly up to about a week before we replaced it.
Ford’s fuel pump driver modules are like that, too. A F-150 gets towed in for a no start, and the FPDM looks like this:
ford-trucks.com/forums/attachment.php?attachmentid=147275&stc=1&d=1463187048
And it was still working properly the day before, although it surely didn’t look much better.
5042040
I should probably check if any of my current fleet has those airbags. I don’t think they do, but I’m not sure. And I would be pretty bummed if my airbag sent shrapnel in my face instead of a nice soft pillow of air.
5042056
Or else being covered in mud and possibly horse manure isn’t good for them.
I’d think that the mud (and manure) might have helped to keep some of the salt off, honestly. Hard to say, though.
That’s one of those things where a bit of red locktite might not be a bad idea, too. One of those places were I often use it--most customers do get upset when the steering wheel comes off in their hands.
You gotta love it when the automaker hasn’t yet figured out the full extent of the problem. GM’s TSBs on the intake gaskets were like that--I did a bunch, but always had to look up the instructions, ‘cause every few weeks they’d change torque values, whether you were supposed to use new bolts or not, whether you needed to put sealant on the threads or loctite or nothing. . . .
5042084
I don’t know if they could pot it. It broadcasts and receives, and I think that the traces on the left and right are the antennas. That’s also why it’s got to be behind the bumper cover; it wouldn’t work if it was behind a metal panel.
Yeah, and that’s one reason I like taking things like that apart when possible. Even if a customer doesn’t completely understand how it functions, they can understand that it shouldn’t have fuzzies growing all over it.
5042451
Toyota also had Massive issues with V6 head gaskets on 2 different models of truck engines. By the time I left Toyota, I was heartily sick of V6 head gasket jobs.
5042532
Yeah, that’s the one thing that sucks with working at a dealer.
When I was at a Chevy dealership, we had a really crappy team salesman, so we wound up with a bunch of recalls and warranty work, and that really sucked.
5042444
So working as intended then. Gotta love car companies.
5042465
Why did I click that link.
Why did I click that link.
WHY DID I CLICK THAT LINK?!
5042585
Pretty much.
On the plus side, it keeps me employed, so there’s that.
5042627
So you could have a little reminder of why you don’t fasten aluminum directly to steel in an environment where there might be salty water present?
Poor Ford, forgetting galvanic corrosion was a thing. GM still remembers, after having rear bumpers fall off lots of their cars.
5042040
5042466
I actually got REALLY lucky with those airbags.
I was in a low speed crash (My own fault) and when the airbag deployed, while I don't think a true rupture occurred (Although I maybe wrong, see below) I didn't escape entirely unscathed.
My arms now feature scar tissue from the chemical burns of the airbag. My left arm also ended up with minor lacerations, but I can't tell if that was from the airbag or perhaps something else.
The odd thing is, as I learned latter, Airbag vents are meant to be at the top of the wheel in modern cars.This was a mid-2000s car so surely the vents should have been up the top. And yet these vents were at the sides.
Hard to know if my injuries were caused by the airbag because according to a brief google 1.5% of people get chemical burns from an airbag deployment so it could be just bad (or good, as again, the bag didn't rupture) luck.
But yeah....less then a week later, the Australian Government began its recall. And the Holden Motor Company keeps asking for us to recall the car, despite the fact it has been written off, and the air bag already deployed.
5044215
Indeed, that sounds like you were very lucky. I know a guy at work who was in the process of beeping his horn at a car when he hit said car (or said car hit him, it's not clear what happened). He ended up with a broken wrist and minor head injuries from the airbag going off.
Much better than the alternatives though, I guess.
5044215
The thing a lot of people don’t know about some of the safety equipment on a car is that it might injure you, but it still prevents greater injury (at least overall; obviously, specific circumstances might vary). It has to work fast, there’s a lot of g-force it has to deal with in a limited amount of space, and it’s not going to be comfortable. That’s just the nature of it, unfortunately. Unless the automakers can get people to wear four- or five-point harnesses, crash helmets, HANS devices, and put up with a roll cage in the car, they do the best they can with what they have. Maybe some day I should do some more reading on that topic and give some actual numbers . . . it’s actually quite a fascinating subject, although since I’m on the repair side of things, I don’t know all the engineering behind it all.
The airbag hits hard and it’s hot. Minor burns probably aren’t unusual. If your car was less than a decade old, it probably had seatbelt pre-tensioners, too, so it might have yanked you back in the seat before the airbag blew . . . I don’t know for sure what the specific triggering events for those are, honestly.
They do try their best to keep things from flying around the cabin that might injure you--obviously, they can’t control what you put in the car, but they do tether down pillar covers and center trays and whatnot so the airbags don’t launch them. And how you’re holding the steering wheel might make a difference in what injuries you might get.
It’s not a perfect system . . . but in all honesty, I’d rather walk away from a car crash with minor injuries rather than be carried away in an ambulance with major ones.
5044348
I got to get one of the alternatives in this:
cdn.discordapp.com/attachments/255810000650371073/567523082600841218/172242_1709950823186_1014698_o.jpg
Notice how the cab is nearly intact, and if I had been wearing a seat belt, I would have walked out without a scratch.
I wasn’t, ‘cause I was dumb, and it’s lucky I have a very thick skull and got away with no lasting injuries from this wreck.
5044995
Oh I denied none of those things. Its quite possible that none of my minor injuries were caused by the fact it was a faulty Takata airbag but instead just because it was an airbag.
As I said, 1.5% people who are in a car accident end up with minor burns, either from the vents or the temperature involved. Given that Takata airbag's have killed people, 'minor chemical burns' is the fundamental definition of good fucking luck.
5045001
Ouch, that crash looks nasty as all hell.
5045067
You did seem reasonable in the comment
, but I figured that was a good place to put out some of the tech stuff for readers that come along later. In all honesty, I’m amazed that the safety stuff generally works, especially when you consider the environment it’s in. My 2002 minivan’s airbag will probably work as intended if I crash it [not that I have any intention of trying], and that thing’s 17 years old, has a quarter million miles on it, and I doubt the airbags have ever been maintained in any way whatsoever.
And you’re completely right, I’ll take seat-belt bruises or chemical burns over serious injury or death any day of the week, and I’m glad that your airbag worked at least well enough to not give you a shrapnel burst instead of a somewhat cushioning pillow.
It probably wasn’t the worst, all things considered, but I did get to ride to the hospital on a backboard and got a MRI so they could make sure I didn’t have a subdural hemotoma (I didn’t). Luckily, that’s the worst crash I’ve been in thus far, and I hope that stays the case.