Where is the electronics for the ABS on a 1996 ?

[scholzee]

I have a 1996 2dr Blazer 4x4, besides the ABS unit under the hood, is there another module with electronics for the ABS. I know you need a special code reader for ABS is it still hooked to the OBDll port to read the ABS codes ?

[ricksza]

The module under the hood is the only one for the ABS. It also connects to the PCM on the other fender. The only other componants are the speed sensors, one on each front hub and one in the transfer case.
Yes the ABS is tied into the Data Link Connector along with the PCM.

[scholzee]

Thanks I am trying to chase down an ABS problem. My ABS light will come on when the speedo gets above 8-10 mph. I tried a different transfer case sensor and that did not help. Both front wheel sensors are clean and no breaks in the wire. If I check with a multimeter at the connector by the upper a arm each sensor is putting out pulsing voltage when I spin the wheel. My sensors are riveted and I heard you need to buy the whole hub to replace them. My brakes actually stop great without it, and I plow with the truck so having them work maybe more of a pain while plowing, not sure how many $$ I want to invest to fix them.

[BlazerLT]

Originally Posted by scholzee

Thanks I am trying to chase down an ABS problem. My ABS light will come on when the speedo gets above 8-10 mph. I tried a different transfer case sensor and that did not help. Both front wheel sensors are clean and no breaks in the wire. If I check with a multimeter at the connector by the upper a arm each sensor is putting out pulsing voltage when I spin the wheel. My sensors are riveted and I heard you need to buy the whole hub to replace them. My brakes actually stop great without it, and I plow with the truck so having them work maybe more of a pain while plowing, not sure how many $$ I want to invest to fix them.

Clean your front hub speed sensors.

[ricksza]

The reason the light comes on around 8 mph is that the system does a self test at that speed. Like BlazerLT said, the problem could be metal shavings built up on the front wheel speed sensors. If that doesn't correct it, get the codes out of the system and I'll get the diagnostics for it.

[scholzee]

Its in the middle of my post but I did clean the sensors and exciter ring. They did not look to be dirty, but used a brush to clean the ring and carefully some brakeclean on the senor and ring followed by a good blast of compressed air to get rid of any particles. I do get pulsating voltage from each sensor but I do not know if its the correct amplitude. Does any one know the air gap on the sensor ? Can the local shops read codes or is it a dealer only thing ?

[ricksza]

The sensor should have a resistance reading of about 1k ohm. I would think that the outside shops should be able to read the ABS codes as long as they have the correct software.

Here's a Service Bulletin from GM that might help:

Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set.
Cause
The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface.
Correction
Measure AC voltage and clean wheel speed sensor mounting surfaces.
Raise the vehicle on a hoist.
Disconnect both the front wheel speed sensor harness connectors.
Place a DVM across the terminals of each sensor connector.
Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's.
If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor.
Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service.
Clean the speed sensor mounting surface on the hub to remove rust and corrosion.
Important
Make sure that the sensor sits flat on the hub. If the sensor flange is distorted, replace the sensor.
Apply a thin layer of bearing grease to the hub surface prior to sensor installation.
Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub.
Install the rotor, the caliper and the wheel.
Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's.

[scholzee]

Ricksza Thank you that is the kind of information I was looking for. Do you know what years that TSB covers ? It also states about low speed activation, I actually have no activation but will give it a try, if that does not work I will get the codes read. Thanks again !!

[ricksza]

It's bulletin #02-05-25-006A - (Nov 26, 2002) and it covers 1995-2003 Chevrolet Blazer, S10 and other models.