ABS Light Comes on at Start-up

[Rivernut]

Lots of issues with my Vue lately! Anyway...2003 Vue AWD V6 98,000 miles. The ABS light has been turning on at start-up. If I shut the car off and re-start it, it sometimes corrects this. The warning light is not coming on while driving except for the first 10 seconds or so after start-up. The warning light is remaining on about half of the times after starting. There are no other warning lights. The car runs fine, and has no bearing noise that I can detect. Sears replaced all of the tires and performed a 4 wheel alignment the day before the first occurance. About a week prior to that I did a rear brake job that required some hammering to remove the drums. I also tow a boat and the rear wheels have been in the water recently submersing about half-way up the wheels, but it has always been used in this fashion. From what I have read here so far, it sounds like I might have a bad sensor, a bad bearing, a bad ground, or an alternator on its way out. What do you guys think? Is there something about performing an alignment that might have damaged something? What tests can I perform or what should I try to troubleshoot this? Thanks.

[enginebrake]

I doubt after driving the truck after a week it would be a problem at the rear sensors so based on the fact SEARS worked on it the day before, jack it up and inspect the plug, wiring and harnesses at the front wheel speed sensors, looking for anything that got pinched, disconnected or hammered. If you see anything that can not be reconnected like a broken sensor, or wire, take it back to Sears and file a complaint.

[Rivernut]

I checked / unplugged / replugged the four wheel sensor connectors. The wires leading to the sensors look fine. The battery is the original Delco with the green dot glowing, the voltage is 12.86 while off. I topped-off the break fluid even though it was okay. I pulled the ABS fuse and cleaned the connectors. The ABS light remains on from about 50% of the start-ups. Is there anything that is done durng a front / rear alignment that comes close to the wheel sensor wires? Is Sears off the hook yet? At what point am I forced to have a dealer troubleshoot it? Any ideas?

[Rivernut]

Now the ABS light stays on everytime the vue is started. There have been no other electrical issues, car seems to run fine. If it is a wheel sensor, is there a way I can troubleshoot it without buying four of them?

[fdryer]

In general, if there are four wheel sensors for your ABS and you hammered the rear drums to remove them I wonder if the hammering shocked one of the rear sensors silly enough to disable it. If you can measure the resistance of the sensors and compare one against another you might find the one that reads different from the others, including the front one's. I'm not sure if these sensors can be measured for resistance though. Perhaps somebody has their FSM's or Chilton's in hand to reference them for you from the wiring schematics.

[Rivernut]

I checked the resistance and there is none. It occured to me while I was checking the first one that the sensor is probably just a coil that receives a magetic pulse each time the wheel turns, so there should be no measurable resistance, and there wasn't. I would have to spin the wheel with a volt meter hooked up to see the pulses. It probably requires some threshold / peak voltage that I would not be able to capture on my volt meter. I have been waiting for the alternator to go bad, it hasn't or the wheel bearings to get loud, they haven't. I feel unmotivated to go to a dealer for an expensive scan and I don't want to randomly replace sensors & bearings hoping That I hit the offending part earlier rether than later in the money bleeding experiment. Come on you Saturn tech gods, toss me a cookie!

[fdryer]

All wheel sensors will read resistance with an ohmmeter, approximately 800-1700 ohms. If you are reading an open on one sensor, compared it with another sensor that reads resistance then the open sensor has failed or been damaged by physical mishandling. My FSM for the L-series describes the resistance values for these sensors and I presume they are generally the same sensors used on your Vue as well as S-series and all vehicles with ABS/traction control. I would measure all the sensors as you have several to compare one against another before hypothesizing. The ABS system performs a self check automatically when the ignition key is turned to the ON/RUN position simultaneously lighting up the ABS indicator. In a moment or two if it has determined that nothing is out of the ordinary then it extinguishes the ABS light. A lot goes on the moment the ignition key is turned to the ON/RUN position. the ABS is just one electrical/electronic subsystem along with the main EFI system that undergoes system self checking before and during start-up. This occurs every time the key is turned. So when you have a constant ABS indicator on its telling you something isn't right; most likely a wheel sensor or sensor wiring is compromised as they are the most vulnerable by physically being located at the wheel hubs. The sensor wiring also runs from the main ABS computer to the wheel hubs and are subject to shorts or cutting inadvertently by anyone unaware of small wiring that may be covered by road debris. An open/cut two-wire sensor harness will also disable the ABS and keep the ABS light on.

All the dealer service tech will do is use more sophisticated tools to arrive at one or more sensor(s) failures and/or wiring failures quicker than you or I since we don't have a Tech II $$$$$ scanner in our toolbox to point the way. Since a whole system scan is done you'll be paying for professional services using trained service technicians with skills to find and repair what most DIYers cannot do because of limitations. After all, you're going to someone that's paid to find and fix what's wrong, not for baseball scores.