Tesseract

Hey all!

I have spent a great deal of time here. I have installed, upgraded and fixed so many things and issues by reading these forums. I generally don't need to post my own threads, but now I'm a bit perplexed.

Like many, I used to have an intermittent ABS/TCS C1214 code that would come and go. This made complete sense when I had removed and cracked open the EBCM to discover a cold solder joint. And I mean it was glaringly bad. I did a simple solder fix to only that one pin and reassembled everything.

The car fired right up and worked perfectly. I tested the car and yanked the steering wheel to ensure Active Handling kicked in and all was well for multiple drives.

Then the car sat for a while. Probably around 2-3 months. The battery failed and I managed to jump the car and take it for a spin. This is where things get weird...

The ABS/TCS dash lights came on. But to my surprise it wasn't the C1214 code, but:

PCM P1571
TCS NO COMM.
SDM U1040

And as I drove the car for about 5 minutes, suddenly the ABS/TCS light went off and it was fine. I stopped at a gas station concerned and turned off the car. Upon turning the car on again, the ABS/TCS light came back on and has been that way ever since. (Same above codes)

Concerned it was the battery, I went and bought a brand new battery tonight and installed it. Still the same problem with the same codes above.

I inspected all the fuses and they are perfect. And I also pulled the EBCM connectors and reseated them. They don't appear to be corroded or have any visual problems. And the ground points all appear to be snug and not corroded or too dirty.

I'm just really perplexed right now. I had this problem completely fixed and now it's worse than the C1214 code all of a sudden. Can anybody shed some light on this? What steps should I take at this point? Is the EBCM toast? And is it common for them to die like this? Or is it a higher likelihood that it's something else?

Oh and the EBCM has two connectors. The large one with the big gray swivel lock and then a smaller one near the bottom. What is the difference between these two cables?

I would appreciate any knowledge and feedback on this! Thanks in advance guys!

dadaroo

What year is your car?

PS: Here is a link to someone with a similar issue as yours. I don't have time now to digest what they say but look at it and I will later. I just found this by searching Google on your SDM U1040 code.

https://www.corvetteforum.com/c5-tec...questions.html

Tesseract

Hey dadaroo,

Sorry, the car is 2003.

I found and read a lot of those threads, and from what I could find it was usually a connector problem. But in my case, everything was working fine until all of a sudden, it went NO COMM.

What's especially weird is how one time, while it was NO COMM it fixed itself while I was driving. And that was the last it ever worked. So I am hoping those are some clues to somebody who might have experienced this and has an idea what's going on.

Thanks for the help!

Tesseract

The guy in that thread really did have a similar problem to mine. I find it really odd this happened after sitting for a while and the last thing I did was fix the C1214 code in the EBCM.

I could check the ignition switch, but I'm curious why the NO COMM issue would have gone away WHILE driving if it was the ignition switch?

Bill Curlee

I’m confused. You stated that you have a 1214 DTC "AGAIN" Is that true????

If so, you still have an internal power issues with the relay inside the module or the power circuit in the module OR the circuit isn’t getting the correct power.

The NO Comms issue can be caused by a LOW VOLTAGE in the power fuses for the module OR a ground issue.

Use a DC Volt meter and actually MEASURE the voltage that is being supplied to all the fuses and the voltage that is actually getting to the main connector on the EBTCM. While you have that connect or disconnected, measure the RESISTANCE on all the ground wires in the main connector tpo battery ground (on the battery and at the chassis)

Hope this helps.

Bill

Tesseract

Hey Bill!

I just got done reading all of your threads, helping others with electrical issues, along with your schematics and ignition switch information. Thank you for all the contributions you have made on these forums!

Nope. Not true. This problem all started last year with intermittent 1214 codes. I removed the EBCM myself and opened it up and discovered one severe cold solder joint. (And by that I mean, it barely had solder at ALL)

Now keep in mind, I had also bought the relay and I still have it. But I DID NOT solder in the relay. Because when I soldered the cold joint and tested it on the car, it solved the 1214 problem. "Don't fix what ain't broke" right? So I bolted the EBCM back on and got everything all put back together and the car worked perfectly. I cleared the codes, and literally had no other codes or problems.

Then the car sat for a few months. Battery died. Started the car with a slow charger, and BAM, the car immediately started with these codes:

PCM P1571
TCS NO COMM.
SDM U1040

If I clear the PCM and the SDM, they stay cleared. But if I cycle to TCS and try to reset it, it blinks and comes on with NO COMM and that's when the PCM and SDM flash THEIR codes. So it definitely seems TCS related.

I haven't started the process of running my DMM across fuses yet. So after work tonight, I will have to take a look at some of this and go through some of your older posts.

Thanks for bringing out the big guns and replying Bill! If you can think of anything with the information I have provided, please feel free to post!

Tesseract

Bill,

I found a post I made, back in August when I fixed the 1214 code with a picture. Click here to check it out.

That was in August. The car sat until about November when I first encountered the NO COMM issue. Believe me, the 1214 code would be a blessing compared to this NO COMM crap.

Thanks!

Bill Curlee

OK.... Now, Im clear on the DTCs.. Check the voltages on the fuses and from the Main Connector for the EBTCM and the continuinty on the grounds from the EBTCM connector.

IF,,,,,,,,,,,,,,,,,,,,,,, The voltages and grounds are GOOD,,,, The module may be bad...

There are other checks that you need to do// You can do a continuity test from the Module Serial data wire to the STAR connector in the passengers foot well to the LEFT of the BCM.

BC

Tesseract

Ok, voltage across the brand new battery is 12.40 volts.
And voltage at each and every fuse is 12.36 volts.

I want to check the voltage and GND continuity at the EBCM connector but there are two. The large one with the gray locking bar and then a small one connected at the bottom of the EBCM. Which cable is it and which pins?

Bill Curlee

LOL

The small one on the BOTTOM of the module is just power to the ANTI LOCK Pump Motor.. No Issues there/

The MAIN connector on the INBOARD SIDE of the module is the one that you need to concentrate on!

Tesseract

Yeah I just figured that out lol. I found it on first and last pin of primary connector. And guess what?

Reading 12.6 volts.

This doesn't sound good. I'm ready to bet the EBCM fried.

dadaroo

No way I can add guidance to what Bill Curlee has and can provide. The only thing I now caution people on when dealing with suspect connectors is to make sure that all the individual pins are firmly seated and not loose. Recently resolved a years long issue with a BCM and IPC issue on one car because of loose pins causing problems. Had one loose pin at the BCM and 2 at the IPC. Hard to detect unless you inspect every one.

Tesseract

Definitely good advice. I work in Information Technology and can't tell you how weird it is that connectors or even cables suddenly stop working. In fact, just recently my wife's laptop spontaneously died and after a lot of troubleshooting, I narrowed it down to the SATA cable of all things.

So these issues haunt me and I have inspected the pins on the EBCM and the connector housing connecting to it. I just can't see anything wrong with it. I never had problems with it and the fact that the TCS went NO COMM on me while sitting in the garage is peculiar.

In fact, I actually emailed Brandon over at ABSFixer and I was surprised to find out that he has seen this issue many times when reviving a Corvette from a battery tender. He also said there simply is no fix for a NO COMM status. It sounds bizarre but I do find it extremely odd that so many stories on these forums and the web begin with "The battery died and after charging it..." The rest is history.

At this point, I'm just not sure what else to check. The voltages and the grounds are all perfect. Couldn't ask for better readouts. And this pains me, because a new EBCM costs $550 at least. That makes any grown man cry a little.

CamminC5

I had a similar issue. Fixed the EBCM (with Bill's help) it was fine for a while, then all of the sudden 1214 came back. I ended up replacing the module (got one from the guys at vettenuts.com, if not on the site call them) and no issues since. Good luck with the fix!