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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3320
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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2005 Chevrolet c8500 with a c7 cat. ABS light is on with no

Customer Question

2005 Chevrolet c8500 with a c7 cat. ABS light is on with no active codes, have replaced dash, and abs ecu. it is a bendix ec30 unit. Bendix is telling me that there is nothing wrong with the abs system, something on the truck side is causing the light
to illuminate
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 2 years ago.

My name is ***** ***** I will assist you.

Are you using a scanner to access the vehicle to pull code on both the OBD and the J plugs? If so, which scanners are you using? I ask because a lot of time I am only able to pull codes up with the Tech 2 Tool scanner or the JPro.

Have you done the other checks on the vehicle like checking for power and such? I'm presuming you have air brakes since this is a EC30 unit. Have you checked the wheel sensors to verify they are all pushed in?

If this is on the vehicle side, most likely the chassis module can;t see the ABS module which is what is giving the dash light. The scan tool on the chassis will be needed to see what code it has to then see if the harness needs to be chased or if there is some other issue going on. This will not be an easy task to work with. If the ABS module is getting power and isn;t coding, then that system will be working properly. It will then be in the chassis module where the code is because it can't see the ABS module. Worst case scenario is to disable the light behind the dash until the chassis module can be repaired or scanned to determine the error.

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Customer: replied 2 years ago.
I have jpro, acom bendix, and cat programs to communicate. Cannot use tech 2 since it has a 12 pin deutch connector. Has no codes in any of the modules, abs system works fine, if I unplug a sensor then it throws a code, and also shows that the light should b triggered on according to my scanner. When I plug the whl spd sensor back in the code clears and it commands the abs light off, but the light stays on on the dash. Could you possibly get me the pin out diagram for the actual dash/instrument cluster?
Expert:  Jeremy replied 2 years ago.

I'm still working a road call, but as soon as I get in from it, I'll post one. I should have one. I apologize for the delay. I didn't wxpect this wreck to take so long.

Customer: replied 1 year ago.
Were you able to get that pin out for me?
Expert:  Jeremy replied 1 year ago.

I sent this 3 times now and the other times it didn't show on my end. I'm trying this again as a bulk instead of splitting page by page. Hopefully it works this time.

Expert:  Jeremy replied 1 year ago.

Yep, looks like it finally wen through this time. This setup just kicked off on our end so we are still working out a few kinks with sending files, but now I figured out what I ned to do.

This is the full pinout for the full cluster that I was able to pull off of GMC. I hope this works for you.

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