Weird ABS problem that stumps dealer

What were the codes? If the codes are for the right front wheel and they've replaced the sensor and checked the harness, time to replace the tone ring, or most likely the whole hub if they're like mine.

 

Does the tone wheel run true?
Is the wheel bearing preload set correctly?
Does the sensor go out of adjustment?
Have they checked the scope pattern from both front sensors at the ECU?
Have they tried running a temporary twisted pair from the sensor to the ECU?

 

If there was an ABS problem, it wouldn't be setting off the traction control light at the same time. Especially a front wheel.

There's a common denominator of the two circuits somewhere, whether it's the ECU, a wire short or instrument panel.

Don't think all dealers are experts either. I been to some that were clueless of the problem and go to the next and they find it right away. Alot has to do with the technicians expertise.

I would try a different dealer.

 

first of all! what a code in MID 136 PID FMI format?

what brake ECU (Wabco ABS-E, E+, Knorr/Bendix, ore EBS with ESP)?

and a good advice - check bearing for play and tires for ballancing, size, wear. Rattle may cause ABS/EBS throw bad polering codes.

 

I usually don't see both the ABS and Traction Control light both come on with a sensor failure or modulator failure. I do see both come on with a traction control problem or communication problem. Having this phenomena happen at a certain distance interval is very interesting. I have never of it. The abs ECU is one of many electronic devices connected together through a communication data link. I have see several times where another component is faulty and causing some havoc for other devices. Bendix ABS ECU's are too sensitive to very minor electrical inconsistencies. Their fault trigging tolerances are too low and they set codes very easily. If your truck has a Qualcom or other satellite communication try to disconnect it. Also if your truck has a data display for engine information, or vehicle navigation, compass or anything like this they may share the same data link with the ABS ECU. Try to disconnect these devices one by one if you can. Also try to disconnect the alternator positive lead at the alternator and see if the problem says or goes away to determine if the problem is being cause by something else.

 

new Wabco ABS units (really made in Wrozlaw, PL) are not interferece sencetive, so bad alternator cant cause this kind of problem. But bad bearing can! If pole ring was tested and it is ok, may be... bearing play, kingpin play, disballanced tire....

MID 136 saves bad speed signal code if the signal is really bad.

This truck is relativelly new, so Wabco S+ sensors are used. Better magnet, better insolation! The only electrical problem I belive is bad extention wire. It is cheap thing. I use to change it with sensor.

 

Yah, we don't see too many Wabco systems around here anymore. I think Volvos use something different from that too. I wonder if something mechanical is the issue the fault is occurring only every 8 km? This may be how long it takes for the code to be triggered so faults don't get logged for minor glitches I guess.

 

do you know how to identify control unit?