P38 ABS Sensor Voltage Irregularity

[StangGT5]

The ABS/TC lights have been on in my 2000 Range Rover 4.6 HSE since I bought it, and they are not going without a fight.

My Hawkeye shows current and historical codes 4125 and 4065 for "Sensor Left-Hand Rear short to another sensor." I cleared them, but the current code stays. In live data, the other three wheel sensors read a steady voltage between 2.35V and 2.37V sitting still. The LR sensor would sit at 0.00V, then quickly fluctuate, then back to 0.00V and repeat.

I replaced the sensor with an aftermarket sensor from AB. The new sensor showed voltage, but it frequently fluctuated in the 2.06-2.45V range. I pulled the sensor and found the tone ring was wet. Upon removing the bolts for the hub, water began draining from the cavity the tone ring sits in. I pulled the axle, cleaned the tone ring and its housing, and reinstalled.

The LR sensor voltage now remains steady for longer, but it eventually begins fluctuating. It will start out at 2.29-2.35V like the other sensors, then move between 2.06-2.45V. I tried swapping back and forth with the factory Wabco sensor and the aftermarket sensor, but there is no significant difference in voltage values or fluctuation. They both start out steady when monitoring live data, but after about 10secs they show minor fluctuations.

Any ideas where to start next? I have a 2002 parts 4.6 HSE truck that I THINK has a good ABS computer.

 

[simondewing]

First off clean the pins in the sensor plug or replace it.
If that does not work try measuring resistance of from the sensor plug back to the SLABS ecu and wiggling the connector/wire , possibly a broken wire somewhere.
In my experience 90% of ABS sensor faults have been the sensor plugs.
Got so sick of these I used sensors with extended wires and hard wired back to the SLABS ECU on one of our 2 discos

 

[discostew]

I think your going to have to break out a meter and a schematic.

 

[StangGT5]

Thanks for the help guys. I already cleaned the sensors and tried wiggling the wires with my Hawkeye plugged. Not to sound like a calculus exam, but I noticed no change in the way the voltage was changing.

I confirmed my parts truck has a good ABS computer, so I am going to swap them out before I go wire hunting.

 

[discostew]

Seems like it would be easier to get a meter and figure out where your loosing that voltage. Do you have a schematic for the truck?

 

[StangGT5]

I have the Rave downloaded, but I am not terribly good at chasing shorts. The P38's ABS computer is right behind the glove box, so it is much easier to swap than the Discovery's unit. Looking at the gaggle of wires coming out of it, I decided to swap them and see where that got me first.

It turned out the ABS computer was the culprit.