ABS/Traction Control Light

[IAMCANADIAN]

My ABS light and my Traction Off light are coming on in my Grand Prix. It started yesterday and would stay on at start up and later on would come on a little while after I started driving. Then last night and once today (I only have driven this car twice today) it didn't come on at all and when I did panic stops, the ABS system worked. I have a 2003 Pontiac Grand Prix SE with the 3.1L V6 and ABS with Enhanced Traction System.

[Neanderthal]

What swear words have you tried so far?

[shadams]

You'll have to get it checked, the traction control is part of the abs system, basically works the same as the abs just at opposite times. If you accelerate hard and lose traction, the abs kicks in and applies the brakes to stop the spinning. Anyway, when the abs has a DTC set, it disables the trac system which is why the trac off light comes on. It could be anything from a wheel speed sensor to the EBCM, the module that controls the ABS and anything in between. I would say the most common would be a wheel speed sensor which unfortunately is part of the wheel hub. $$$$!

[IAMCANADIAN]

How much do you think this will cost? What I don't get is that the ETS system is engine based and doesn't use the brakes to control spinning so it's weird why both lights are on because it isn't the engine/brake based system that's on the GTP.

[W.A.F.U.]

How much do you think this will cost? What I don't get is that the ETS system is engine based and doesn't use the brakes to control spinning so it's weird why both lights are on because it isn't the engine/brake based system that's on the GTP.

Both systems rely on each wheel speed sensor reporting back to the pcm. If one sensor experiences an open circuit for even just a tenth of a second, the PCM turns both system off.

My Grand Am started to do this shortly after I bought it used. It would always be the right front sensor error. Bearing was fine so I filled the connector with dielectric grease. Drove the car for over a year after before getting rid of it and the light never did come back on.

[IAMCANADIAN]

I see. If it doesn't seem to get better I'll have to take it in I guess.

[shadams]

How much do you think this will cost? What I don't get is that the ETS system is engine based and doesn't use the brakes to control spinning so it's weird why both lights are on because it isn't the engine/brake based system that's on the GTP.

It uses both on both actually. Option NW9 is traction control and is the same on both cars. The only difference is that the GTP says TCS OFF instead of TRAC OFF, go figure. Anyway, here is how it works.


When drive wheel slip is noted while the brake is not applied, the EBCM will enter traction control mode.

First, the EBCM requests the PCM to reduce the amount of torque to the drive wheels via the requested torque signal circuit. The PCM reduces torque to the drive wheels by retarding spark timing and turning off fuel injectors. The PCM reports the amount torque delivered to the drive wheels via the delivered torque signal circuit.

If the engine torque reduction does not eliminate drive wheel slip, the EBCM will actively apply the drive wheel brakes. During traction control braking, hydraulic pressure in each drive wheel circuit is controlled to prevent the drive wheels from slipping.

[IAMCANADIAN]

Hmm interesting. I'm not looking forward to having to take the car in as I'm not loaded with money right now. Hopefully it won't be too bad.

[big swede]

Most likely it's just a wheel speed sensor but I have seen a bad wheel bearing cause the same thing because of vibration.

[IAMCANADIAN]

Hmm good to know.

[RickMN]

Before you take it in, try inspecting and cleaning the sensor terminals. My scanner showed bad signal at right front sensor on daughter in law's Alero. I disconnected and cleaned the sensor, ran meter checks back to ABS controller, and cleaner the master plug at controller. Applied very light coat of dielectric grease to sensor terminals. Light out for almost a year now.

[IAMCANADIAN]

Before you take it in, try inspecting and cleaning the sensor terminals. My scanner showed bad signal at right front sensor on daughter in law's Alero. I disconnected and cleaned the sensor, ran meter checks back to ABS controller, and cleaner the master plug at controller. Applied very light coat of dielectric grease to sensor terminals. Light out for almost a year now.

I have no clue where the sensors would be. If I hadn't just graduated I'd ask my auto mechanics teacher but unfortuately school's out. I think I'm just going to take it in next week if it keeps on coming on.

[Triple-X08]

wheel speed sensor.

all W cars have problems. had 3 grand prixs they have all had wheel speed sensors that fail.

get a multimeter, check your resistance of each sensor. should be around 1k ohms. if its like 1M ohm, then its junk, or if it reads OL its junk.

[IAMCANADIAN]

Great, thanks for the help. I'll take it in and get the sensors looked at.

[Triple-X08]

no problem