The ABS light on our 2002 GC has been coming on and off lately. i checked and it has a code 20 stored. This is pump voltage issues. I found a post by Mastertech with some troubleshooting and I posted there about it, but maybe this stuff gets buried, so I'll post a new thread. HERE is the link to my other post.

I was able to watch the pump voltage on a graph while driving and stationary and the voltage would randomly jump to 3.2 volts. I also watched wheel speed sensors and they would randomly jump to 88 MPH. They would do this while driving or stationary, but only with the engine running. KOEO and everything would flatline at zero, but sitting there KOER and the speed sensors would randomly jump to 88 MPH.

Any thoughts or suggestions?

 

Every time I have gotten the Pump voltage code, it has been a corroded B+ wire to the ABS module. Usually in a horrible place to get to, like about 12-16" from the module connector.

 

Thanks, tiz. IIRC the ABS module is part of the Hydraulic Control Unit, correct? I think a battery removal is in order for this exploratory surgery.

 

They are bolted together but are separate pieces. Disconnect the module connector and check for power with a test lamp with a bulb in it, no meters or led stuff. It should light bright, if not find the bad spot.

 

Yeah. The fun part is it's intermittent. Always fun.

 

Try hosing it down, if it's just starting to get corroded, the wet makes it worse. Then when it dries it works fine.

 

And look for the spot where some tool used a probe to poke holes in the insulation.

"Hey. Here's an idea: this thing isn't breaking down enough, so I'll poke holes in the insulation so water will get in and corrode things real nicely. Then I can charge a bunch of 'diagnostic time' searching for the problem."

I can see someone doing that, but fortunately that kind of tool isn't around for long.

 

Well, sometimes this Pump Voltage issue on those van are cause by a corroded Power Distribution Center. Try yank on the connector under the PDC, see if it can make the problem happen.


Sometimes you can get away with cleaning the connector, or replace the Wiring Terminal in the connector. But sometimes you need a new PDC.