ABS Issue

[Camo Ranger]

Hey everyone,

99, 3.0 L, 4X4

I've been searching through past threads about this issue and it seems that many have experienced the same problem but no one has posted a definite fix.

My problem is this that when I go to stop (<5mph), my ABS kicks on right before you would expect the truck to stop, causing the truck to go a few feet further than it would normally. Definitely not warped rotors, as this issue has persisted even with the new pads and rotors that I put on less than 1,000 miles ago. Also, usually the ABS light will turn on when this happens and the truck pulls to the left slightly.

To make matters more interesting, randomly my speedometer will start jumping from 0-80mph, the abs light will kick on, and the truck will "buck" almost like the brakes are engaged when the speedo hits 0mph. I tried replacing the sensor in the rear differential and cleaned the connection there, but it didn't help.

I tried scanning for codes and came up with P0503 "Vehicle Speed Sensor (VSS) Circuit Intermittent".

I'm not really sure where to go from here. I would appreciate and suggestions on what to check/replace next. Oh, and the truck does have 4WABS.

Thanks,
Dan

 

[Heavyfire14]

maybe disconnet the battery (neg. cable first then pos.) wait 5 mins the connect it back up. this will reset the computer. if this doesnt work then idk?

 

[Camo Ranger]

Thanks Heavyfire14, but I've already tried that. Replaced the alternator about a month or so ago, so the computer would have reset then when I had the battery disconnected. This issue has been going on since this past spring and has steadily been getting worse/more frequent. Thanks anyway.

 

[Heavyfire14]

sorry mann. good luck.

 

[powerranger262]

Vehicle speed sensor on top of the rear axle. I will see if I have a pic of it.

 

[Camo Ranger]

Thanks powerranger262, but I've already replaced the VSS. May try replacing it again seeing how its like an $8 part.

Does anyone think that maybe a short somewhere in the wires running forward from the VSS could cause my symptoms? That's one thing that I haven't done is to trace wires out.

 

[cr_the_machinist]

My 99 had the same problem. Turned out one of the from wheel speed sensors had gone bad. ABS would engage on dry pavement, especially during turns while braking to a stop. Get the multimeter out and take a ohm reading on both sensors on the steering knuckles. If you get an extremely high ohm reading, theres a short in the sensor (or one circuit if no reading obtainable). Has not happened again since I performed that work, well only when the ABS actually needed to kick in (which is a good thing in my book haha).

Hope that helps.

 

[Camo Ranger]

Thanks, I'll look into that and let you know what I find.

 

[Earl43P]

Send me a PM with your e-mail address and I will send you schematics from the 2000 EVTM.

Your braking symptom sounds like a bad right front ABS sensor (left brake working properly, right is getting pulsed by the ABS, so it pulls to the left), so do that resistance check and compare it to the left side.

The rear axle sensor does feed the speedometer, but its signal is first processed by the 4wABS module, then to the speedo. That rear axle VSS signal goes through the big square connector under the driver seat, exterior of the cab. Clean the corrosion out of that connector and pack it with new dielectric grease. The two wires are LG/BK (Light Green with a Black stripe) and RD/PK.

Connect/disconnect that connector repeatedly to wipe the contacts clean, if you do nothing else.