ABS Pump Runs Constantly, '01 Silverado

[Rhymingmechanic]

2WD, half-ton, 59,000 miles

So I started the truck the other day, and the ABS pump started running and wouldn't quit. Brakes still worked with the pump going--I drove a couple car lengths to another parking spot and pulled the fuse. With the fuse in, the pump will even run when the key is off. I had Autozone check for codes, but their reader doesn't do ABS.

Has anybody else had this problem? I'd like to know what to expect before I take it in. Also, can a good independent shop diagnose and repair this kind of thing, or do I need to go get assaulted by the Chevy dealer?

 

[JTK]

Same thing would happen on ~1998-2001 isusu rodeos (which have mostly GM/delphi parts). They had a recall on it & would basically replace the whole ABS unit (motor/hydrauic block doohicky). Higher end OBDII code readers can read ABS codes, or on some (like the rodeos), there are two pins you can short on the OBDII port and count the *flashes* of the ABS light to decode.

Joel

 

[Matt_S]

There was indeed a recall for unwanted low speed ABS activation on these trucks. The mounting surface of the ABS sensor would become corroded, causing the computer to activate the ABS when it shouldn't. The warranty work involves removing the sensor, plugging the hole so debris doesn't fall in, brushing off the rust, then treating the surface with a rust-penetrating oil and finally using grease when re-installing the sensor. Check to see if this recall has been done. If not, it could solve your problem and you might not have to pay for it, although the recall was technically limited to rust belt states.

 

[norseman]

Send the ABS off to these guys. They will fix it for you at a great price http://www.modulemaster.com/

 

[punisher]

Not quite, ABS activation is different than a pump running continuously.

Track down your ABS pump relay. It might be stuck closed or the primary side is continuously grounded somehow (bad wire or defective module).

 

[Rhymingmechanic]

I think it is the ABS Module. The exact problem is mentioned on some model-specific forums, as is norseman's link.

List price for a new module is over $800. GM Parts Direct gets about $450. Modulemaster says they will repair the original unit for about $150, so I'm considering that when I have time to pull the part. Apparently, the power switch in the module is not robust enough and burns out.

An independent shop I've used can't read ABS codes, and Chevy charges $101. I've done a little research, and it seems like most consumer scan tools don't read ABS. Can anybody recommend a reasonably-priced scanner that reads ABS and powertrain codes, shows data like knock retard and trans temp, and is CAN-ready for future cars?

 

[Jim 5]

I have this one:

http://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=6915

I have been very pleased with it so far. I've used it on my BMW, my Chev truck, my wife's Acura, my Triumph motorcycle (just yesterday to clear a code and get rid of that CEL that the dealer would have charged me $150 to remove), and my friend's Audi.

I haven't been stumped yet. It is CAN OBD II ready. I'm not sure if it would be able to read ABS systems, although I was really pleased that it was also compatible with my motorcycle's ISO 9141 format. I think it will pay for itself if it hasn't already...not just in money but in saved time not spent going to the dealership and back.

 

[Matt_S]

Jim 5's scanner doesn't appear to read Chassis codes, only Powertrain codes. It's an impressive scanner, though. Check this web page. Please double check with the manufacturer about your specific vehicle, but I'm pretty sure this one will do the ABS and air bag stuff as well. The software runs on a PC, though, so a laptop would be very helpful unless you want to drag your PC out to the car to do readings.