Hello,

I'm new to this forum, have tried others with no luck. I have a 2008 with a manual trans and have an issue with my ABS that goes back 3 years. When I start the car, the ABS light and Brake lights come on, and I have no traction control and no power steering. This is an intermittent issue, sometimes the lights will randomly go off and I have no issues. To make a long story short, I have gone through 3 used ABS modules at the recommendation of a local Corvette shop and local dealers and the problem still exists. Currently, when I start the car, the dash lights up, and I get two DTC's:

1. From the ECM: U0121 - Lost Communication with the EBCM
2. From the BCM: U2108 - Lost Communication with the EBCM

The popular answer is to say I have a bad ABS module, which is what the shops have told me. But after swapping out 3 different used EBCM's and still having the same issue, I don't think my problem is the ABS module. When the dash is lit up, and I try to scan the ABS module, I get a message stating my scanner cannot link to it, which makes sense considering the following.

Occasionally, I can start the car and the dash does not light up - everything works including the power steering. When this happens, my scanner will communicate with the ABS module, and I get these DTC's in the history:

1. C0870-00 - Control Module Voltage Reference Output Circuit
2. C0561-71 - System Disabled Information Stored - Invalid Data
3. U2100-00 - CAN Bus Communication

When I read these codes, it makes me think the ABS module is getting an incorrect voltage from another source, and thus is shutting itself down.

Does anybody have any thoughts or insight on this? I think the right person with access to the schematics (which I do not), and maybe a scope, could diagnose this problem but I have had no luck finding somebody in the metro Detroit area. If somebody knows exactly which circuit the C0870-00 DTC is referring to, I could at least try to find a schematic of that circuit and try to diagnose myself.

Thanks,
Scott

 

Have you tried checking the big blue fuses under the passenger floor board? A lot of people report those being loose and once they push down on them it solves the issue. If that doesn't work, I would check/clean all the grounds. Battery connections, especially the ground too. I've recently dealt with ABS/Active Handling bs. In fact my ECBM is at ABS Fixer right now getting repaired. I had C0121 code though, not what you have. I feel for you man, it's pretty frustrating.

 

Yes, I have checked the big blue connectors on the BCM, and the Vette shop here went through all the grounds. I originally had the C0121 code as well, and sent my original EBCM to ABS fixer. He made the repair, but the problem didn't go away (the C0121 was gone, but then all the other problems started). ABS Fixer said there was evidence of brake fluid on the circuit board - that was the start of all the EBCM replacements. It is very frustrating, and very expensive - I'm into this for thousands already. Good luck with yours, hope ABS fixer solves your issue, and thanks for the reply.

 

Haha, not exactly what I was expecting to hear!!!! We will find out here in a few days