01 Grand Prix 3.8: Been getting the ABS light on constantly (also the traction light). From what I've read, a bad wheel sensor is usually the cause. Is there a way to diagnose it? There are no DTCs set according to my code reader, but is there some other type of code that can be read with a more specialized type of scanner? Or maybe use a multimeter? I'd rather not just start replacing parts, since replacing a sensor requires replacing the entire wheel hub, and none of the hubs are making noise yet (at 110K), not to mention that new ones aren't cheap.
how to diagnose ABS problem
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You probably need a more advanced code reader to access your ABS codes.
You could try your local auto parts stores. All the ones around me have scanners you can use for free. Some of them are sort of advanced and have some ABS capabilities.
You could try your local auto parts stores. All the ones around me have scanners you can use for free. Some of them are sort of advanced and have some ABS capabilities.
The value of the ABS sensor is "digital", a magnetic / capacitance sensor that detects the teeth on the ring so you cannot use a multimeter to check.
If anything the most you can do is look at the counter reading in ECU. Something like this you might want to go to a model specific forum and ask other members there.
If anything the most you can do is look at the counter reading in ECU. Something like this you might want to go to a model specific forum and ask other members there.
Set your e-brake.
Jack up one front tire.
Idle it in drive. Should get ~ 10 MPH on the speedo.
Listen for the ABS self check, and see if the lights come on.
Repeat with the other side.
If it doesn't do the check, and doesn't light the light, that sensor is no good.
Take note, traction control might want to lock the spinning wheel which will send a jolt of power to the on-ground wheel. I'd put a hefty chock in front of said wheel so you don't jump off the jack.
Hover over the service brake and stop the spinning tire firmly before you put it back in park.
Jack up one front tire.
Idle it in drive. Should get ~ 10 MPH on the speedo.
Listen for the ABS self check, and see if the lights come on.
Repeat with the other side.
If it doesn't do the check, and doesn't light the light, that sensor is no good.
Take note, traction control might want to lock the spinning wheel which will send a jolt of power to the on-ground wheel. I'd put a hefty chock in front of said wheel so you don't jump off the jack.
Hover over the service brake and stop the spinning tire firmly before you put it back in park.
Without a real scanner do it the poor mans way....
First, does the light come on IMMEDIATELY or after say 15Mph? At 15Moh the motor and pump are tested. You should hear a faint click or feel a tiny bit in your pedal(true for fords, but yours should be similar).
A light coming on immediately and staying on is likely a dead sensor or bad connection.
Disconnect abs sensors..
measure resistance for each sensor while you wiggle the wire. Should stay constant at around 2Kohms(check service manual).
Set the meter to AC voltage, Then spin the wheel, should get a signal of about 300-500MV at 1 rev/sec. (again general guidelines).
Finally(you can't always do this) inspect the tone rings for each sensor. Sometimes they are in the bearing and could be corroded or broken.
First, does the light come on IMMEDIATELY or after say 15Mph? At 15Moh the motor and pump are tested. You should hear a faint click or feel a tiny bit in your pedal(true for fords, but yours should be similar).
A light coming on immediately and staying on is likely a dead sensor or bad connection.
Disconnect abs sensors..
measure resistance for each sensor while you wiggle the wire. Should stay constant at around 2Kohms(check service manual).
Set the meter to AC voltage, Then spin the wheel, should get a signal of about 300-500MV at 1 rev/sec. (again general guidelines).
Finally(you can't always do this) inspect the tone rings for each sensor. Sometimes they are in the bearing and could be corroded or broken.
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^P.S If the light is on before you are in motion you can skip the A/C spin test. There is a hard static fault in the system.
Originally Posted By: PandaBear
The value of the ABS sensor is "digital", a magnetic / capacitance sensor that detects the teeth on the ring so you cannot use a multimeter to check.
If anything the most you can do is look at the counter reading in ECU. Something like this you might want to go to a model specific forum and ask other members there.
What? On this car checking for a dead sensor is the easiest thing to do. Just connect the ohm meter on the sensor wires, the one with 0 or much lower than the others is the bad one.
This is not an active WSS sensor.
http://www.aa1car.com/library/diagnosing_abs_wheels_speed_sensors.htm
http://www.brakeandfrontend.com/diagnosing-wheel-speed-sensors/
The value of the ABS sensor is "digital", a magnetic / capacitance sensor that detects the teeth on the ring so you cannot use a multimeter to check.
If anything the most you can do is look at the counter reading in ECU. Something like this you might want to go to a model specific forum and ask other members there.
What? On this car checking for a dead sensor is the easiest thing to do. Just connect the ohm meter on the sensor wires, the one with 0 or much lower than the others is the bad one.
This is not an active WSS sensor.
http://www.aa1car.com/library/diagnosing_abs_wheels_speed_sensors.htm
http://www.brakeandfrontend.com/diagnosing-wheel-speed-sensors/
Also if these have the traditional 2 prong weather tight connector, those tend to metal fatigue (into non-conducting) the conductors right where the wire pulls against the plastic shell.
If you can scare up some known good connectors, splicing those on could be cheaper than visiting a real mechanic.
If you can scare up some known good connectors, splicing those on could be cheaper than visiting a real mechanic.
Originally Posted By: eljefino
Also if these have the traditional 2 prong weather tight connector, those tend to metal fatigue (into non-conducting) the conductors right where the wire pulls against the plastic shell.
If you can scare up some known good connectors, splicing those on could be cheaper than visiting a real mechanic.
Yes, it is important to wiggle test wires.
Also if these have the traditional 2 prong weather tight connector, those tend to metal fatigue (into non-conducting) the conductors right where the wire pulls against the plastic shell.
If you can scare up some known good connectors, splicing those on could be cheaper than visiting a real mechanic.
Yes, it is important to wiggle test wires.
Thanks for all the suggestions.
The light does stay on from when the car is started.
Tried eljefino's jacking up the wheel test first since that was the easiest. The light stayed on for the test for both front wheels, so I guess that means it's probably one of the rears? I'm assuming they also have sensors. Will try the multimeter and wiggling the wires.
The light does stay on from when the car is started.
Tried eljefino's jacking up the wheel test first since that was the easiest. The light stayed on for the test for both front wheels, so I guess that means it's probably one of the rears? I'm assuming they also have sensors. Will try the multimeter and wiggling the wires.
Another thing to keep in mind is that layers of rust can form between the steering knuckle and ABS sensor. The air gap would be too wide to make the ABS function properly.
It is sometimes called "Rust Jacking" and if that is your problem, scrape away the rust and then reinstall the sensor.
It is sometimes called "Rust Jacking" and if that is your problem, scrape away the rust and then reinstall the sensor.
Originally Posted By: neo3
Thanks for all the suggestions.
The light does stay on from when the car is started.
Tried eljefino's jacking up the wheel test first since that was the easiest. The light stayed on for the test for both front wheels, so I guess that means it's probably one of the rears? I'm assuming they also have sensors. Will try the multimeter and wiggling the wires.
It could be smart enough to also read the speed from the transaxle differential gear.
Or I like the non-conducting connector idea more the more I think about it.
Thanks for all the suggestions.
The light does stay on from when the car is started.
Tried eljefino's jacking up the wheel test first since that was the easiest. The light stayed on for the test for both front wheels, so I guess that means it's probably one of the rears? I'm assuming they also have sensors. Will try the multimeter and wiggling the wires.
It could be smart enough to also read the speed from the transaxle differential gear.
Or I like the non-conducting connector idea more the more I think about it.
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