After two months on the quickjacks, my 08 C6Z was all back together with it's new heads, cam, and intake. Start the car - dead TPMS. I was annoyed, but I know the sensors don't last forever. I was also getting a service traction control error as well. Didn't think much of it, since my alignment is a little off after having lowered the subframe.

While driving my car to the tuner, I now get a warning message saying the ABS needs to be serviced and now have an ABS light on the dash - lovely.

Pulled the codes and received C0040 for the right-front wheel speed sensor. I looked at the live stream data, and it reads 0mph, so I have to assume it's bad. Just replaced the hub yesterday, made sure to hit all connections with contact cleaner (including the EBCM connector), and STILL have the code. Now, I go back and check for continuity the from the sensor, through the aux harness, and into the main harness.....I have continuity, so no breaks in the wires. Now I'm annoyed! Before, I could start the car and no lights would pop up until the car was over a few mph. Now, it's on the moment I start it. Even if I clear it, it comes right back.

The only other thing I can think of is the Universe felt like kicking me in the nuts and decided to kill my EBCM? Is there anything else I should check before I spend the money on a replacement EBCM?

Any help/insight is appreciated. I'd really like to enjoy this car, but damn my wallet is getting thin!

 

GM switched from Delphi ABS to Bosch ABS in 2009. The speed sensors are incompatible. If you have a late hub in your early car, it won't work. What is the part number of the new hub?

 

Local dealers did not have FRONT hub in stock, so I went with an Autozone part:


I just looked up this exact part number and listed the car as a 2011, and it says it’s not compatible. This leads me to believe I have the correct part.

 

513139 should be the right part number for early ABS.

You checked continuity end-to-end. Did you check for a short circuit? Unplug both ends and make sure neither wire is shorted to the other wire or to ground.

 

I pulled the EBCM connector and checked continuity from there (used a paper clip as a jumper), to the end of the harness on the car. Then I checked continuity from one end of the aux harness (that plugs into the wheel spared sensor) to the other . I then checked from the end of the aux harness, back to the EBCM connector. Continuity each time.

Not sure how to check for a short. Any advice on how I should do that?

 

When unplugged you want to confirm there's essentially infinite resistance (no continuity) between either wire and ground, and between one wire and the other.

For good measure, switch your meter to voltage mode and check for voltage between either wire and ground. There shouldn't be any.

 

Inspect the wiring. You can often visually locate a short.

I once disturbed a rear sensor wire while doing some work. It eventually came in contact with the exhaust and shorted.

 

Okay, so here's what I've done tonight:

Checked for a short to ground - passed
Checked for short together - passed
Checked the new wheel speed sensor creates voltage when spinning at the EBCM connector - passed
Checked the OLD wheel speed sensor created voltage when spinning at the EBCM connector - passed
Checked for continuity throughout the entire path from the sensor to the EBCM connector - passed.

I also had the one bad TPMS sensor replaced, since I read a bad TPMS can cause some weird stuff to happen - same result.

At this point, it HAS to be the EBCM - right? Both new and old wheel speed sensors create voltage when spinning by hand as verified at the EBCM connector so that rules out the wiring and the wheel speed sensors...that only leaves the EBCM...or am I missing something?

EDIT: I also checked the ABS module fuses - they're good. I can also hear a "click" from the ABS module when I do a module reset, so I know there's communication happening, but still getting the C0040 code coming from the ABS module immediately after clearing.

 

Administrators. Why can't I delete this post?

 

UPDATE:

It was the EBCM!!!! I was able replace the EBCM without having to pull the ABS pump. Took a little less than an hour to get it done.