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I have this 1996 Chevy K2500, a 5.7L engine, automatic trans and 4WD. The issue is that the amber antilock brake light is on in the dash. There is multiple codes in the ABS Module for wheel speed sensor signal missing at all wheels, erratic wheel speed on all wheels, relay circuit shorted, and a watchdog code. When I try to erase codes, they simply do not disappear. I have tried replacing the module with the same results. Same codes and same inability to erase codes. I have good solid power and good solid grounds to the module. And as per MOD diagnostic process, it says replace module. However, that doesnt fix it. What am I missing?

The ebcm? What are the codes? Have you LOAD tested the wiring to the ebcm? Did you program the tire size? Id want to know the ebcm is bad before replacing that way if I got a defective part we would know that.

The codes are C0035 - Rear Speed Sensor Open or Grounded
C0022 - RF Speed Sensor Signal Missing
C0023 - RF Speed Sensor Erratic
C0066 - Open Or Shorted Pump Motor Relay
C0073 - EBCM Memory Error
C0086 - Shorted ABS Indicator Light
C0025 - LF Speed Sensor Circuit Open
C0021 - RF Speed Sensor Circuit Open

As I mentioned, when I replaced the EBCM, I have the same problems, same codes and they cannot be cleared with my scan tool.

You replaced the EBCM with a *new* unit or used?

It was a used unit Ric. "new" and or reman is not available. We even sent the one we took off to a place that can check and rebuild them if need be. They said that there was nothing wrong with the one we sent to them.

I should mention that in viewing data, the wheel speed sensors all show something over 6 million mph. Identical numbers for all. It does seem that the other data is correct.

VIN please?

Also, I did see a TSB for a revised testing procedure for code 66. Did you see that?

Did you load test the wiring or just use a dvom? Did you test the wiring to the speed sensors? Have you tried a different scan tool?

ricmorin wrote:VIN please?

1GCGK24R6TE151509

ricmorin wrote:Also, I did see a TSB for a revised testing procedure for code 66. Did you see that?

I did not see a TSB that is applicable to this vehicle for DTC 66 although there is one that is for DTC 67, 68 that is for the S10.

Tim Martin wrote:

ricmorin wrote:Also, I did see a TSB for a revised testing procedure for code 66. Did you see that?

I did not see a TSB that is applicable to this vehicle for DTC 66 although there is one that is for DTC 67, 68 that is for the S10.

My mistake.

So you replaced the EBCM? yes? There are 2 components that make this assembly IIRC. The hydraulic part and the computer part. I'm wondering if the hydraulic part has a problem which in turn is causing these codes in the computer part. Theory is: something shorted in hydraulic part causing voltage pull-down which wigs-out the computer.

According to the wiring diagram, there is a third player called the vehicle control module. Looks to be an interface for the VSS to distribute signal. That's a suspect too.

As near as I can tell, the Vehicle Control Module and the Powertrain Control Module are one and the same unit in this application. Correct me if I am wrong. The location is in the left front corner of the engine compartment.

Tim Martin wrote:As near as I can tell, the Vehicle Control Module and the Powertrain Control Module are one and the same unit in this application. Correct me if I am wrong. The location is in the left front corner of the engine compartment.

I didn't investigate that deeply, just an observation. It's certainly possible. Gotta love OEM's and naming conventions. If it was the PCM, just call it that.

What was the fix for this?

brianp87 wrote:What was the fix for this?

Have not brought this challenge back into the shop again. Will post the fix

Any update?