Hello everyone! This is my first post here and I must say thank you to all who have posted about their experiences in their repairs! Those posts have been very helpful but unfortunately haven't lead to me actually fixing my issue.

I have a 2008 2.4L LT with 218K miles. I bought it when it was just over a year old with something like 18K miles. It has been a great car compared to all others that I've had over the years!

Back in April, I replaced the lifters & rockers (they weren't too bad except for that one in the corner of the front left!), VVT solenoids, and the timing chain because I noticed it was stretched when I was in there. I'm saying this to illustrate that I can work on cars. 😆

Around late June or so, when temperatures rose to the 80's and 90's is when crazy things started happening to my gauges while driving! By crazy, I mean the speedometer, fuel, rpms all do intermittent readings and the mileage, coolant temp, and other things in the DIC don't work and the air conditioner wouldn't cool the air. I could pull over, turn the car off, then start it back up and it would be normal. In my technical mind, that tells me that something electrical is starting to fail because heat is very detrimental to electronics. Come August and September it starts to do it more often and then the transmission starts shifting really hard. I go to Advance to get the codes scanned and I get:
- P0700 (Transmission Control System MIL Request)
- P2544 (Torgue Management Request Input Signal A)
- U0073 (Control Module Communication Bus A Off)
- U0101 Lost Communication with TCM.
This Advance guy appeared to be knowledgeable and seems to think my TCM is bad and said, "although they typically don't go bad, I think the TCM is going bad." I do some "research" and order one from an online store. They programmed it according to my VIN. Replacing it didn't fix it. Same old song. It seems worse as each day passes and then, sometimes the car wouldn't even start and the security light started coming on! 🤬

I buy a cheap code scanner so I can keep monitoring these codes and I'm still getting the same ones. After I'd check something below, I'd clear the codes and see what would show up.

I know the U0073 code is the key and it means there is a problem with the GMLan data wires that allows the modules to communicate with each other.

Here are things that I've done and made sure of (based on common suggestions from other threads):
- Battery has been load tested and is good. 12.67 volts at rest. Alternator ~14.3v
- Grounds G103, G107, G109 in the engine area have been cleaned and I even re-terminated G103 as it was corroded pretty bad even at the crimping.
- With the battery disconnected, I've unhooked, inspected, and cleaned using electronic cleaner (that's safe for harnesses) the connectors of the TCM, ECM, EBCM and even replaced the Camshaft Position Sensor Connector because it sat right under the main harness and appeared to have been in a bad bind. (I ended up using two long zip ties to keep that main harness from falling back down onto it.)
- Checked the grounds under the driver's seat and under the dash.
- Cleaned the harness connectors under the dash.
- Cleaned the power steering motor connectors since the DIC displayed "power steering" when it got crazy.
- I've ended up replacing most of the fuses in the BCM even though they weren't blown, they appeared burnt, but is really a type of corrosion.
- Cleaned the 5 connectors of the BCM.
- Took apart the fuse box in the engine compartment and everything appeared fine. I didn't put dielectric grease on the terminals though. At the time I didn't think it would be wise to do, but then found a TSB on these forums that suggests doing it! I might still do this sometime but I seriously doubt it will fix the problem.
- I've had every recall (including the ignition switch) done except for the recent one about the latch on the dash compartment.
- I have 61 ohms resistance on pins 6 & 14 of the OBDII connector (battery disconnected.) ~120 suggests a failed component.
- I've also used my oscilloscope on pins 6 & 14 to ground to view the waveforms and both appear to be normal. When the gauges do their erratic dance, both the high and low waveforms appear crazy and I can't get a trigger on any of them because of how whacky they are.

I can't find the post, BUT someone suggested unplugging the ABS unit. Guess what... THAT FIXED MY GAUGES!!! Seriously! I took out the 3 fuses in the engine compartment for ABS and everything has been working perfectly normal--except for having the ABS, Brake and Traction Control lights on. No codes have been thrown for 3 days now!

I have discovered through trial and error that fuse 61 for the ABS is the culprit and I believe that powers the EBCM module. I can't find an actual schematic for the EBCM circuit for a 2008 2.4L and I have seen conflicting information that it appears the 2008 is somewhat different than other years? I don't know if that is true or not.

I've seen some youtube videos of people taking apart the EBCM unit on some Silverados and Corvettes and reflowing some solder joints that typically break. (I have good soldering skills.) I attempted this yesterday HOWEVER I can't get that little panel cover off! I used a razor blade to get in there but it just wasn't separating. I think there is a vast difference in how these are physically constructed and bonded than the other (and a bit older) GM modules in those videos. So I put it back on the car and left the three fuses out. I've thought about using a hot wire to melt through it as I could use epoxy to bond it back, but there's no guarantee that there are any broken solder joints!

Perhaps I should find someone that has or buy a scanner that can read the ABS/EBCM module to see exactly what is at fault. The problem would be that when the gauges are funky, I can't even connect with the plain OBDII scanner so will it even be able to scan the ABS unit while the gauges are messed up?

Upon discovery of this, I tested the wheel bearing hub assemblies by supporting the car on jack stands, removing the tires, replacing the lug nuts to secure the rotors and disconnected the hubs. I then hooked my voltmeter to the terminals and had my son slowly and steadily accelerate with it in drive. I got consistent readings on both hubs so I'm assuming those are good. I replaced both of them about 2 years ago when one failed.

Does this make sense to anyone? It doesn't make logical sense to me because why would the ABS/EBCM unit cause the codes I listed above in relation to the TCM? Also, why would "turning off" the ABS make everything work perfectly fine?

I never had ABS until this car so maybe I'll just put black tape over those lights and go retro. 😆🤣😂

Thanks for reading my book and am hopeful that someone else has had this same problem and fixed it. My gut tells me the EBCM is shot.

 

I believe it was hellshotrod who determined the EBCM ABS and gauges issues. Thanks for posting up the results of your tests and inspection.

https://www.chevyhhr.net/forums/prob...scanner-64706/

 

I just posted a long post about my problems, but your suggestion has confirmed the problem I was having is involved with the EBCM. Would you care to share the information about the shop that repairs them?
Thank you!

 

There are 3 fuses to the EBCM:
here is a pdf of the schematic:
ebcmschematic.pdf

 

Thanks. Yeah, I can have 44 and 57 in and everything is fine, but plug in 61 and it gets crazy.
The text in that pdf drawing is very pixelated and hard to read everything, but it appears 61 would be related to the wheel speed sensors as it is grouped with them.

I'm going to find someone with or buy a scanner to try to scan the ABS system.

 

JeromeC

Thank you for your detailed write up. I have a 2006, bought new, with 185,000 miles and I have been having same issues over the years of and on. Recently they are showing up more often. Like today I went out and unlocked the car with my key since my fob stopped working years ago and as usual the horn went off but as soon as I get in and put the key in and start it up, the horn (security measure) stops. Today though the gauges were doing their thing again, jumping all over, low fuel, lock showing and ABS blinking off and on and no power steering. I had my scanner with me but it was unable to establish communication so I couldn't get any codes.

After checking battery voltage, alternator output, and fuses under the hood they were all good, I shut the engine off with the gauges still doing their thing.

I got out, hit the lock button on the driver door and closed the doors. Waited a few minutes, unlocked the door again, to the sound of the security horn, got in, started it up and the gauges were fine. Everything was back to normal, except the check engine light was on.

I put the scanner in and got two codes: P0700 (Transmission Control System Malfunction) & U0073 (FSC Can Bus Communication Bus "A" off).

I don't know what to think, but I am like you. I replaced the front hubs last spring and new wheel speed sensors and for awhile no problems, but they are back now. In December 2021, I also had the first two codes plus a couple others. C0561 & C0550 (E Control Software Malfunction). I will go out tomorrow morning, start it up and see what happens. Also will try the fuse idea the next time it happens to see if that corrects things. Thanks for your post. I was surprised to see such a recent and detailed post.

 

You're welcome and good luck. Before starting tomorrow, pull fuses 44, 57 and 61 from the engine compartment and see what happens. I would be willing to bet that the gauges are fine afterward. You won't have ABS or traction control though. I've been driving it since this post without them and have not had any issues.
I've been busy and haven't had the time to try to take apart the ABS unit. I will though. I should have some time coming up soon. I'm willing to bet there is a broken solder joint on the board. I'll report back here when I get to it and if that was the issue or not. Let me know if pulling the fuses takes care of your gauges. I'm curious.

 

u have a bad abs brain , i have had a lot of 08,s with the same prob ,and 09,s , just need too pull it and send it out for repair i did find a shop that does it as most won't ,

the place is module master there in moscow idaho .. we have had great luck with them

 

Yeah, I'm sure it is a problem in the ABS unit since removing it solves the symptoms. Why not just post the shop's info so everyone can have access to it?

 

Like here, for the 2009 model year

https://modulemaster.com/pages/product-result