97 ABS issues

[gmctruck06]

Having brake issues with my 1997 Blazer. Replaced a wheel speed sensor a week ago and now the abs actuates on almost any road condition. No codes are present. Cleaned the sensor targets and still having problems.replaced the actuator. No dice. Any assistance would be greatly appreciated.

[shorod]

Did you use a scan tool that can access ABS codes, or the standard powertrain scan tool off the parts store's shelf?

-Rod

[gmctruck06]

I should have stated that there are no trouble lights lit at present. Had it in the shop to diagnose and read codes for the speed sensor.

[gmtech1]

Colorado Springs, nice place, used to live there. Did you have these problems before the hub was replaced? If it was a cheap, aftermarket hub, that may be the problem. Whats happening is that the ABS is sensing wheel slip (lock up) on low speed braking. With a capable scanner, you can monitor the the wheel speed and see which one is dropping out and causing the ABS to engage. Sometimes though, the speed drop is so fast that the scanner will not read it and you will need to watch the valve operation in the ABS data list to see which valve is activating first.

[j cAT]

Originally Posted by gmctruck06

Having brake issues with my 1997 Blazer. Replaced a wheel speed sensor a week ago and now the abs actuates on almost any road condition. No codes are present. Cleaned the sensor targets and still having problems.replaced the actuator. No dice. Any assistance would be greatly appreciated.

most likely the other sensor.

low speed ABS activation is most always a dirty or damaged sensor/wires/connector.

disconnect the sensor connector attach a volt meter AC VOLTS at low range to measure 1/2 volt. rotate the hub by hand at a good rate and see if you have more than .3volts ac. compare both sides. a new sensor properly set into place should read a full .5volts ac.


OVER .3VOLTS SHOULD WORK. UNDER THIS VALUE NO.

[gmctruck06]

I will try to disconnect and rotate by hand to see if that is the issue. I will post back results as soon as I can get this done. Thanks for the advice gmtech1 and j cAT

[gmctruck06]

Finally got to test both sensors this weekend. both sides showed .7 on the multimeter with the meter set to test low volts ac. Have cleaned both sides to be sure that dirt is not an issue.

[gmctruck06]

Have read other posts, seems like main issue is dirty sensor. Since these sensors are integrated into the dust shield, they can't be pushed away from the sensor ring, not sure where to go from here. May just have to take it back into the shop to see what they say I guess.

[j cAT]

Originally Posted by gmctruck06

Have read other posts, seems like main issue is dirty sensor. Since these sensors are integrated into the dust shield, they can't be pushed away from the sensor ring, not sure where to go from here. May just have to take it back into the shop to see what they say I guess.

so by cleaning the sensors and you got .7volts ac on both sensors with the hub being rotated , then ABS Light still came on ?

the sensors must be close to the encoder sensor ring. if too far the signal generated will be too weak.

make sure the sensor wires that go back into the carbody wiring are not damaged.

[gmctruck06]

Not getting any abs or brake light. Just get the abs pump to actuate at low speeds. Now, after a test drive recently, the abs pump actuates at about 30 mph without braking. Have double checked all wiring and all seems OK. Originally, before replacing driver side sensor everything worked fine. Replaced driver sensor because of a worn through wire.

[gmtech1]

Ahhh...it's a 2wd then? Take a close look at the tone rings (the notched ring that runs by the sensors) make sure they are not cracked through in any place and that the cogs are free from any debris. If they are cracked the can cause all kinds of problems.

[j cAT]

Originally Posted by gmctruck06

Not getting any abs or brake light. Just get the abs pump to actuate at low speeds. Now, after a test drive recently, the abs pump actuates at about 30 mph without braking. Have double checked all wiring and all seems OK. Originally, before replacing driver side sensor everything worked fine. Replaced driver sensor because of a worn through wire.

with the pump coming on at the higher speed and not in the braking mode the abs control module must be bad. see if you can get one from a scrap yard.

[gmctruck06]

The blazer is a four wheel drive model and the tone rings are good. Did clean the rings and sensors, found nothing out of the ordinary. Current abs control module is from a scrap yard since I "assumed" the original part might be defective.

[j cAT]

Originally Posted by gmctruck06

The blazer is a four wheel drive model and the tone rings are good. Did clean the rings and sensors, found nothing out of the ordinary. Current abs control module is from a scrap yard since I "assumed" the original part might be defective.

if the both ABS control modules have the same problem and the sensors signal is as you revealed then , the wiring/connectors must be the cause.

[shorod]

On two Malibus ('97 and '99) as well as a Venture minivan (don't know the year) I've experienced issues with the right front wheel speed sensor reading low when coming to a stop with ABS activation. Typically this was worst on rainy days. On the 1997 the owner actually wanted it fixed and I found a bad connection at the wheel speed sensor along with 18 inches of corroded wire between the sensor connector and where the wire met the subframe. It appeared that the sensor connector was not sealed very well so moisture and road salt was able to get in to the connector and corrode the copper wire. I had to cut back 18 inches to find wire that was good enough for me to solder to. It all went back together with adhesive-lined shrink sleeving and RTV where the wires entered the connector housing.

-Rod