Wheel Bearing/Speed Sensor?

[redzmonte]

Im going to put it on the lift tonight and see if anthing is out of line but when i go over small bumps and touch the brakes no i feel the peddle vibrate and sometimes the Low Track light comes on indicating the abs is activating... now it has not done this untill yesterday but now it does it pretty religiously. My guess is wheelbearing with speed sensor (Looks as if they come as a single unit together unlike the W-bodies) is going bad. I don't get a ABS or a brake light or anything the abs reacts very easily. Any other possibilities i should be looking at? I know alot of guys run Timken brand, any experience with MOOG? i know moog products are usually good but not sure about their bearings

S

[smokinssei02]

Every now and then I have the same issue and every now and then (usually after I drive down a bumpy road) the service engine soon light comes on. Once it said Left Front WSS input = 0.. Most recently:

LR WSS input = 0
RR WSS input = 0
And something about some kind of dynamic proportioning system or something like that was offline... sort of concerned.

[redzmonte]

Had a tec scan it and both wheel speed sensors seem to be working correctly. There is apparently a bumpy road sensor or something. Anyone know what that is and how to replace it?

[redzmonte]

He said it may also be called a g sensor, it was measuring the G's caused by the bumps.... It went from Like 1-3 gs going down the road to like 99 when I hit a small/medium bump.

[Archon]

This is a description of that system.

The PCM uses the Class 2 serial data line to communicate with various other components and systems within the vehicle. The PCM ensures that communication remains established by monitoring the Class 2 serial data circuit for State Of Health (SOH) messages from the other devices using the circuit. If the PCM detects a loss of the SOH serial data message from the Electronic Brake And Traction Control Module (EBTCM) , the PCM stores DTC P1602.

The PCM also receives rough road information from the EBTCM on the Class 2 serial data circuit. The PCM uses the rough road information in order to enhance the misfire diagnostic by detecting any crankshaft speed variations caused by driving on rough roads. This allows false misfire information to be rejected. The EBTCM calculates the rough road information by monitoring the ABS wheel speed sensors. If a malfunction occurs which does not allow the EBTCM to transmit the correct rough road information to the PCM while a misfire DTC is requesting the MIL, DTC P1380 sets. If a loss of communications causes the PCM to not receive the rough road information while a misfire DTC is requesting the MIL, DTC P1381 sets.

Under certain conditions, the PCM has the ability to command the EBTCM to shut off the traction control via the Class 2 serial line. The following DTCs cause the traction control to be disabled, an ABS/TCS DTC to set, and the traction OFF lamp to illuminate:

DTC P0101 - Mass Air Flow System Performance
DTC P0102 - Mass Air Flow Sensor Circuit Low Frequency
DTC P0103 - Mass Air Flow Sensor Circuit High Frequency
DTC P0171 - Fuel Trim System Lean
DTC P0172 - Fuel Trim System Rich
DTC P0200 - 206 Injector Control Circuit
DTC P0300 - Engine Misfire Detected
DTC P0336 - 18x Reference Signal Circuit
DTC P0341 - Camshaft Position Sensor Performance
DTC P1374 - 3X Reference Circuit

The dynamic rear proportioning is also controlled by the EBCM.

Dynamic Rear Proportioning (DRP)
The Dynamic Rear Proportioning (DRP) is a control system that replaces the hydraulic proportioning function of the proportioning valve in the base brake system. The DRP control system is part of the operation software in the EBCM. The DRP uses active control with existing ABS in order to regulate the vehicle's rear brake pressure.
TO C1248 sets in order to indicate that the EBCM illuminated the red BRAKE warning indicator. The EBCM cannot perform DRP due to another fault in the ABS/TCS system. DTC C1248 will never set by itself.

[redzmonte]

Thank you for that information. which leads me into my next questions, do i look at the EBCM or is it just reacting to a bad reading somewhere? the scanner did say when the abs activated and the low trac light was on the DRP activated, which i would assume is normal when the abs is working.. I have no Codes, no "Brake" or "ABS" light come on when this all occurs, only a Low trac light and abs activation as if it were on gravel or ice and slipping.. (on bone dry pavement). now it happends when im on the brakes or off the brakes but mostly when i go over a small/meduim bump but has happend when turning left (not so much going right) on smooth ground... Got me confused... but i can easily recreate it.

S

[Archon]

If I had to guess, I would lean more toward one of the WSS not reading properly. It may be tough, but see if you can determine which wheel causes the symptom when it hits a bump. Another consideration is that the suspension can not keep up with the bumps. I've had some trip the service stability system when one of the rear wheels hit a bump due to weak shocks.

[redzmonte]

i am leaning toward the RF bearing... seems to be the most common tire to hit when the issue happens... the rear suspension is new and it seems to happen when the front bumps.. i have a bearing ready to go in, just need to get it on the lift and tear it apart i guess.

Thanks!
S

[redzmonte]

car is going in monday. scanned the WSS again and all 4 are reading fine.. no codes. my mechanic things its going to be a yaw sensor or steering angle sensor or some shiznit. will find out on monday i guess.

[redzmonte]

My mechanic said it looks like a bad yaw sensor.. Anyone have a problem like this? Wanna make sure before I spend te money for a new one (quite pricy) we are looking at the right part. I pmed hero already about a replacement. Anyone have one go bad?

[00Beast]

Yep, my 00 had both the yaw sensor and SWPS out. The yaw sensor is easy enough to replace, a couple bolts and a quick connector.

[redzmonte]

cool. i hope its not both. its strange that the sensor(s) are not causing a Code.... i guess they are broke but broke within spec's

[redzmonte]

New yaw sensor in... So far so good! I love a cheap fix!