1999 Pontiac Grand Prix, 96,000 km's, 3.8

GALMAGIE

MEMBER
1999 PONTIAC GRAND PRIX

When I start the car in the mornings and start to drive away my ABS and LOW TRAC lights come on. I only got the car a few weeks ago and it's been doing this right from the start. When I got the car it needed new brakes all around.
If I stop the car and turn it off for a few seconds, then start to go again the light stay off. Any idea on what could be causing this problem.

Thanks

7 Replies

CLY

MECHANIC
308 POSTS

Have the car scaned for codes at a local parts store and let us know what codes they pull from the computer. That is kinda strange that it only happens when it sits overnight. Does it sit outside? Maybe something to do with moisture geting into a connector?

Cly

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Friday, August 3rd, 2007 AT 6:15 PM

SERVICE WRITER

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What is happening is that the computer is not seeing any live data when the car is off. You start the car and the computer and the sensors hang out and talk about not moving. The car starts moving, and 3 wheel sensors say "hey, I'm going 10 mph" and anothe one says" I'm not moving moving I'm still at 0 mph". The computer says "until you agree, I'm throwing a code and a light".
When you shut it off, they all say they are at ) miles an hour until you move again.
You'l probalby need a bearing/hub unit, but don't rule out a sensor.

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Friday, August 3rd, 2007 AT 8:35 PM

GALMAGIE

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4 POSTS

The car is parked in a an underground parking lot each night, so I don't think that moisture is a problem

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Saturday, August 4th, 2007 AT 9:35 AM

GALMAGIE

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4 POSTS

Thanks, I'll have a look at the bearing/hub unit, but I'll also check out the sensors

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Saturday, August 4th, 2007 AT 9:43 AM

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Start with pulling the codes. Critical to getting through this most effeiceintly.

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Saturday, August 4th, 2007 AT 11:50 AM

GALMAGIE

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I have had the codes's scanned and the fault code was for the ABS Traction C0051/C0050 Right Rear Speed Sensor.
So I guess that this sensor is easy to replace?
I had a loot at the sensor and when I unplugged it water came out of the plug end. The ABS and TRAC OFF light stays on all the time now.

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Saturday, August 18th, 2007 AT 11:21 PM

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No, don't condemn the sensor yet. Get some electrical cleaner and spray both the connector and the sensor plug. Let it dry. Get a good look at the pins for corrossion. Spray it again and work it in and out to free up corrosion or what have you. Then spray them separatly and let the dry. Then spray some dielelectric grease in it and reconnect it. Then drive it and see if the light goes out.

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Sunday, August 19th, 2007 AT 7:08 AM