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SERVICE VEHICLE, ABS, TRAC OFF lights come on, no stored hard codes, clears each time vehicle is turned off

Tiny
JSWATERS99
  • MEMBER
  • 2004 PONTIAC GRAND AM
  • 42,725 MILES
The problem I'm having is that the service vehicle (not service engine), ABS, and Trac Off lights come on. There are no codes stored to the computer, with or without lights on. If I spin the tires, low trac light comes on as designed, then off when I throttle back. Tried several hard stops, abs pulses brake petal as designed. I can clear it in neutral while rolling, kill the car, start back up (while still moving) and it never comes back on again until I kill the car. The next time I drive it, they all come on again. There's no difference in handling, low mileage, very well taken care of. Sometimes will go all day and not turn on however, but usually when it does it's in Reverse, or directly after going from reverse to drive. If I start the vehicle in Neutral, and shift to "3", instead of "D", get up to speed and then put in "D", seems to not happen anymore. Again, no stored codes after trying all the above steps to trouble shoot it (per many others responses) Already took it to a dealer as well, no trouble codes/hard codes in computer. Dealer could not answer as everything checked out. I had the tires and brake pads replaced at 37K. (Original Goodyear 40,000 mile tires, so first tire replacement) At 41900, had the tires rotated and balanced. This problem started up a few days after the tires were rotated.

signed,
I have no idea
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Friday, October 14th, 2011 AT 7:04 PM

17 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 33,752 POSTS
GM has a real common problem with the front wheel bearings developing a little play. That play is perfectly normal, but with their built-in wheel speed sensors, that's enough to cause the signal to drop out intermittently. You can find that by watching the four wheel speed readings with the scanner, on a test drive. The scanner will likely also have a "record" feature. You press the record button when the problem occurs. Since the data travels through the scanner's memory, the recording actually begins a couple of seconds before you press the button. Later, you can play the recording back to watch what the computer is seeing.

If you look in the dealer's scrap metal bin, you'll see dozens of front wheel bearing assemblies. The signal dropout problem often starts with only 15,000 miles on the bearings.
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Friday, October 14th, 2011 AT 8:43 PM
Tiny
JSWATERS99
  • MEMBER
  • 10 POSTS
Caradiodoc,
I have a random question based on your reply (might even help a few other folks). Since the dealer inspected mine and said there was no readings "out of tolerance" levels, and with so few miles, no hard codes, etc. Would it be feasible or practical to re-torque the hubs? You know, like the break in on a vehicle often will tell you to see a dealer to have certain parts re-torqued after say 500 or 1500 miles. Second. Most of the time this happens, I'm not even moving. I can go in reverse, then hit drive. And DING DING DING, the lights go on. LOL I've seen some responses on these board forums that noted the same, and others it only happens as they gain speed. My case, simply stopping, hit the brake, lights come on, or hit drive and lights come on, but not actually moving. So hub or speed sensor I would think wouldn't duplicate this symptom, but I'm a "shade tree" mechanic. But the dealer couldn't tell me either. So hoping to find it on this forum. Again, many thanks!
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Friday, October 14th, 2011 AT 9:08 PM
Tiny
CARADIODOC
  • MECHANIC
  • 33,752 POSTS
If the problem occurs when the car is standing still, that rules out a signal dropout problem, cracked tone ring, (on other car brands), mismatched tire sizes, and things like that. That leaves electrical things that are monitored by the computer. One of the anomalies of GM cars is they can turn on warning lights without setting a fault code. That can be real frustrating and is where the scanner on a test drive comes into play.

If you want to try something that sounds silly, unplug the small connector on the side of the generator, then drive the car and see if the lights turn on. Since this design was first used in 1987, they put out a pile of huge voltage spikes that can destroy the internal diodes and voltage regulator, and they can interfere with computer sensor signals. If by some miracle that solves the lights turning on, be sure the wheel speed sensor wires are routed in their original locations, then try a new battery. As they age, they lose their ability to dampen and absorb those voltage spikes. That very often leads to repeat generator failure. Engine running problems are often solved too with nothing more than a new battery.
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Friday, October 14th, 2011 AT 9:50 PM
Tiny
JSWATERS99
  • MEMBER
  • 10 POSTS
Actually, I never thought of that. Low miles yes, but it is 7 years old, and the original A/C Delco battery. I will try that tomorrow and post the results. One other note (may not mean much), they didn't drive it while they did their diagnostic. It was on some roller thing in the bay, so the tires could free-spin/accelerate without the car actually moving (but couldn't duplicate the problem), I always wondered if the difference was simply pulling weight of the car, and not on free-spin. LOL. I'll try the alternator trick tomorrow. Again, thank you kindly!

V/r
Jim
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Friday, October 14th, 2011 AT 9:59 PM
Tiny
CARADIODOC
  • MECHANIC
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Did they have all four wheels turning and at the same speed? If they just ran the two front ones on a hoist, the traction control would constantly kick in.
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Friday, October 14th, 2011 AT 10:03 PM
Tiny
JSWATERS99
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Not a hoist. They drove up on it (front wheels only), still level to the ground.O__O <--tire went in between the two rollers. Not sure what they call it.
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Friday, October 14th, 2011 AT 10:17 PM
Tiny
CARADIODOC
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That sounds like a chassis dynomometer. We used to have one at school but they took it out because it never got used. The mechanic would have had to turn off the car's traction control to just run the front wheels. All they could do would be to watch the front wheel speed signals. They were probably expecting to see one of them drop out.
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Friday, October 14th, 2011 AT 10:28 PM
Tiny
JSWATERS99
  • MEMBER
  • 10 POSTS
Caradiodoc,
Tried unplugging the generator. Lights still came on. Went to Autozone and had the battery replaced. Lights didn't come on at that time. I drove it home "hoping" it was solved, but drove it about two hours later (to run to the beer store, LOL). As soon as I backed out and went from "R" to "D", ding ding ding, and lights all back on again. Checked for codes again while still running and warning lights on. Still no hard codes in the memory. So, gonna call it a day and have a beer. LOL

v/r
Jim
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Saturday, October 15th, 2011 AT 7:02 PM
Tiny
JSWATERS99
  • MEMBER
  • 10 POSTS
Oh, one more thing the wife noticed. On the way back from Autozone (that the lights didn't turn on) the car had already been driven 22 miles (there, and 22 back, so 44 miles). Could it correlate to the speed sensor, maybe it was warmed up, and after sitting a few hours and cooled off, lights returned? Would that make any difference?

V/r
Jim
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Saturday, October 15th, 2011 AT 7:05 PM
Tiny
CARADIODOC
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Temperature can make a difference if, for example, the coil of wire in a wheel speed sensor is expanding and pulling a wire off its connection. Corrosion between pins in an electrical connector will change resistance with changes in temperature. A mating terminal in a connector can be spread, (stretched), causing an intermittent contact.

I think I see a more likely possibility though. How are you checking for fault codes? If you're using an inexpensive store-bought code reader, those are for engine codes only. You need a scanner that can access the anti-lock brake computer to get those codes. ABS codes won't be stored in the engine computer.
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Saturday, October 15th, 2011 AT 8:08 PM
Tiny
JSWATERS99
  • MEMBER
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The dealer couldn't get the codes either. But the unit I have has a read code (not running), and a record (while running) and separate test for Milstats, safety devices, EGR/Emmissions, HO2, CO2, ABS, Hot temp, Misfire, and various other test. There's nothing to do with traction control though that I can find from the menu options.I guess I could take it back to a dealer next week and have them try again. Starting to get expensive though. LOL
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Saturday, October 15th, 2011 AT 8:19 PM
Tiny
CARADIODOC
  • MECHANIC
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Traction control is an add-on to the anti-lock brake system. You can't have it without having ABS. Any related codes will show up under the ABS menu.
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Saturday, October 15th, 2011 AT 8:28 PM
Tiny
JSWATERS99
  • MEMBER
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I dunno then. The brake pads were replaced about a year ago at 37,201. The pads were worn more than I would have expected a car with that low of mileage, but even then there were no error codes/lights that came on, but I could hear them so had it checked out. They turned the rotors, checked caliper & such, and replace the pads. Didn't seem to start with the lights until a week or so after I had the tires rotated and balanced. It started out every once in a while. And over the last few weeks had turned into a daily thing. Other than like today if I drive it over a long distance. Sad thing is we bought it new, 2 years later I retired. That said, it really doesn't leave the yard but maybe once or twice a week. I usually drive my truck (or at least drive it more often)

v/r
Jim
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Saturday, October 15th, 2011 AT 8:41 PM
Tiny
JSWATERS99
  • MEMBER
  • 10 POSTS
Caradiodoc,
I figured out or narrowed down the problem, and possibly why they could not duplicate it at the dealer. The wheels were straight. I've always associated it with going from "R" to "D". Today, ****s and giggles I tried another theory. Without changing in ANY gear at all, I simply turn the wheel right. Lights came on. Killed the car, started back up, lights cleared. Then I turned to the left (again, still in park) Ding, Ding Ding, lights on again. That said, kills the speed sensor issue. But introduces a possible new theory. I just can't figure what it would be. LOL BTW, do you guys work for the forum? I always see the donate button, so assuming, specially if I can figure this dang problem out. LOL

Thanks
v/r
Jim
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Tuesday, October 18th, 2011 AT 5:17 PM
Tiny
CARADIODOC
  • MECHANIC
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Turning the wheels will flex the rubbery wires going to the front sensors. Look for connectors that might have loose pins. If the connectors are inside the inner fenders where they really don't flex, unplug them and use an ohm meter right there to measure the continuity while a helper turns the steering wheel. A typical value would be somewhere in the area of 450 to 800 ohms. The exact value isn't critical. You're looking for one that goes open circuit intermittently.
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Tuesday, October 18th, 2011 AT 5:44 PM
Tiny
JSWATERS99
  • MEMBER
  • 10 POSTS
Caradiodoc,
I'll Try that here in the next few days. The weather is turning south, so to speak, here in South Cacalaky. I will certainly let you know the outcome. I bought the car in Pascagoula MS in 2004, then stationed in Atlantic Beach, NC for 3 years, now here in SC. All near the coast. I'm starting to wonder based on your response if it's the salt air/water (Prior Coast Guard, always stationed on the coast. So would make since it could be as simple as a corrosion problem).
V/r
Jim
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Tuesday, October 18th, 2011 AT 5:53 PM
Tiny
CARADIODOC
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I'm in WI, the road salt capital of the world, and we don't really run into electrical problems due to salt unless the weather-pack rubber seal in the connector is damaged or someone poked a hole in the insulation to take a reading, (never an acceptable method), and didn't reseal it. I HAVE run into corroded connector pins too on cars that are never driven in winter so I suspect water is the bigger issue, but salt isn't going to help.
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Wednesday, October 19th, 2011 AT 3:44 AM

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