2nd Gen Non-Engine/Transmission ABS Oddities

[pjc]

1998 12v, 4x4, auto, sbqc 230k miles, RWAL.



Here are the symptoms:

1. Start truck. No ABS or Brake light on (normal).
   
2. Drive at speeds up to 45 MPH.
   
3. When braking fairly hard the pedal feels like the ABS system is modulating the pedal.
   
   
   
4. Accelerate to 45+ MPH and ABS and Brake light come on.
   
5. When braking pedal is firm at all times.
   
   
   
6. Stop truck and restart and ABS and Brakes lights are out and can re-create whole sequence.
   

What do you all think?



Dirty connector or bad speed sensor?

 

[DavidC]

My 99 was doing that and found that if I removed the plug from the rv plug at the hitch the problem went away. I cleaned the cavities on both sides of the plug with contact cleaner and filled the cavity of the plug with di-electric grease. Since doing this there has not been a problem.



Dave

 

[pjc]

The Trailer plug? WOW! That seems distant but, I'l sure check it as well today. I also use CAIG DeOxit on all electrical contacts. It is awesome.

 

[DavidC]

Yeah, I know it sounds stupid but I was all over the truck trying to figure out why it would only happen around 45mph. Last resort was to unplug the truck wiring harness from the trailer plug and take it for a ride. Bingo, no more problem. There is also a speed sensor in the trans for 2 wheel drive vehicles. For the auto it is on the drivers side just above the trans mount crossmember. Do not know if it would cause a problem with ABS or not but an ohmmeter across the two terminals should read somewhere near 600. If it was the rear axle sensor it would also make your speedo intermittent. The 4x4trans speed sensor I believe is at the transfer case.



Dave

 

[pjc]

I checked all Speed Sensor and trailer Plug wiring and cleaned all connectors and the problem persists. Does anyone have the part number for the rear, diff speed sensor?

 

[DavidC]

Did you put a ohmmeter across the rear sensor?. Should read around 1800. If it does your problem is elsewhere.



Dave

 

[pjc]

1845 Ohms with the truck static. Time to try and read the codes I guess.

 

[SSolderitch]

got the red brake light also?