Troubleshooting ABS light and codes

[bheston]

I just bought a 2005 Uplander, when I bought it the brake and ABS lights were both on. I quickly found a broken wire on the left front ABS sensor and repaired it. I have an OTC Genesis scan tool and I cleared all codes. As soon as I started driving again the ABS light came on. The brake light stayed off. I am getting these two codes now:
C0040 - Right front wheel speed circuit malfunction
C0041 - Right front wheel speed circuit range/performance

I have inspected the wiring and don't see any physical problems at the right front wheel. I can see ABS speed data with the Genesis tool, and I always register a speed on the right front wheel equal to the speed of the other wheels when moving. I have cleared the codes a couple times and one of these two codes keep coming back soon after I start moving.

What can I look for?
Do I just have an intermittent problem that I haven't caught watching the wheel speed in the ABS diagnostics?
I don't want to replace the wheel bearing/sensor if it isn't bad, any ideas how to troubleshoot this further?

TIA, this site is full of great information!

[maxwedge]

If the abs module is telling you it see the proper input for that sensor, then it is a mystery, there may be a momentary high resisatnce that sets the code, check for about 1000 ohms at the sensor connector at 70 degrees.

[j cAT]

Originally Posted by bheston

I just bought a 2005 Uplander, when I bought it the brake and ABS lights were both on. I quickly found a broken wire on the left front ABS sensor and repaired it. I have an OTC Genesis scan tool and I cleared all codes. As soon as I started driving again the ABS light came on. The brake light stayed off. I am getting these two codes now:
C0040 - Right front wheel speed circuit malfunction
C0041 - Right front wheel speed circuit range/performance

I have inspected the wiring and don't see any physical problems at the right front wheel. I can see ABS speed data with the Genesis tool, and I always register a speed on the right front wheel equal to the speed of the other wheels when moving. I have cleared the codes a couple times and one of these two codes keep coming back soon after I start moving.

What can I look for?


TIA, this site is full of great information!

your scanner may be less critical than the vehicle computer with the signal output. since you have codes indicating this right front sensor as the problem I would remove the sensor and clean any contamination.. if the rust is pushing the sensor out of position on the mounting surface file down to clean metal reinstall and test it out.

also check the connector , and wiring to / from sensor for defects.

with a volt meter rotate hub and compare voltage readings on each side..should be the same..

resistance check of both sides when moving the wires/ connections may reveal bad connections..but not help with the abiility to produce the voltage/signal required to properly input speed data to the pcm for proper control

[j cAT]

Where do you park all your vehicles ?

You have alot of problems there..

[bheston]

Originally Posted by j cAT

Where do you park all your vehicles ?

You have alot of problems there..

That is funny. I do have a lot of problems, but I can't claim all of them This one is mine and I just bought it, it was driven on gravel for a while which can be hard on vehicles. I park mine in a garage and try to take good care of them. I also work on vehicles for my parents, in-laws, friends, etc so I can come up with some strange ones from time to time. I appreciate your input j cAT, you usually have some great ideas to help me figure these out!

[bheston]

I am running out of ideas and things to check. I continue to get code C0040. I can clear the code and then drive and it won't come on until I press the brakes once, then I can feel my anti-locks kick in for a quick second and the light turns on.

I have inspected all wiring and even cut the old connector off the right front wheel sensor and installed a new one. I continue to read speed on the right front wheel through the diagnostic computer. If I thought the sensor was bad I would replace the wheel bearing, but I don't want to waste the money if the problem is somewhere else. Is there a chance I have an electronic module that could be bad?

[j cAT]

Originally Posted by bheston

I am running out of ideas and things to check. I continue to get code C0040. I can clear the code and then drive and it won't come on until I press the brakes once, then I can feel my anti-locks kick in for a quick second and the light turns on.

I have inspected all wiring and even cut the old connector off the right front wheel sensor and installed a new one. I continue to read speed on the right front wheel through the diagnostic computer. If I thought the sensor was bad I would replace the wheel bearing, but I don't want to waste the money if the problem is somewhere else. Is there a chance I have an electronic module that could be bad?

when rotating the hub what ac voltage did you get on the left /right side at the sensor connector ???????...
should be over 300MV AC....

[bheston]

I had forgotten to post the solution to this one. I tested the output from both front speed sensors and got about the same readings, so I looked harder at the wiring. I found the pinouts for the harness going into the EBCM near the master cylinder, and checked continuity from EBCM down to the speed sensor. I found continuity only on one wire. I had checked the wiring from the sensor up a couple feet until the wires went into a larger harness, so I don't know where the break was. Chevrolet has a repair kit for this vehicle because this harness was known to fail, but the repair kit is $116 and only includes the connection at the speed sensor and some wire, you have to cut and splice the wire into the main harness. I chose to cut the wire near the speed sensor and near the EBCM and solder a new set of wires in, which solved my problem.

Thanks again for all the help troubleshooting this one.

[maxwedge]

Nicely done!