ABS Module Testing

[Seattleslew]

Good Morning,

Im new to the site and this is my first post here. Ive found a ton of valuable info on the site but am still having some trouble finding the answer Im seeking. We bought an 02 X5 4.4 back in November and about a month ago had the ABS, DSC, and brake lights illuminate for no more than a day or so. They would then go off for a number of days and come back on only to turn off again. When pulling the codes with an OBDII scanner, it returned a code for the left rear wheel speed sensor. The third time this happened,each of these lights were accompanied by an inoperative speedometer.

At this point, I did a bit of research online and found an indy that had the proper diagnostic tools, good customer reviews, and 20+ years experience. I received a call a day after dropping the X5 off to them letting me know that it wasnt actually as simple as a wheel speed sensor and that the ABS module had a "short" in it so the unit needed to be replaced. The advisor went on to say that this would solve my problem once done. I recieved a call back shortly after expecting the vehicle to be ready but instead was informed that the problem had not been resolved and that the 2 rear wheel speed sensors needed replacing.

I say that to say this. The wheel speed sensors are what I figured to be the culprit to begin with so one would assume that the repair would start there, with the less expensive replacement. I understand that the OBDII scan tool is not as comprehensive and that these computer systems can sometimes be finnicky but t the same time have a funny feeling about the ABS module replacement. When picking up the vehicle i asked that the provide me the "shorted" ABS module and they did so with no problem. What I need to know is if its possible to test the old unit in the vehicle w/out having to get the new one reprogrammed again when I put it back in. Ive found the removal/replacement write ups on the site but dont want to jump into testing the old unit unless Im sure I can put the recently replaced one back in with no issues.

Any help by way of suggestion with this would be greatly appreciated.

[JCL]

I suggest you replace the two rear wheel speed sensors, or at least the left one that also drives the speedometer. That is more to rule them out than anything. It is simply the cheapest thing to do to eliminate them as a cause.

The comment that I picked up on was that sometime the speedometer went off with the light (indicating the LR sensor) and sometimes it didn't (indicating something else).

Another possibility is that there is a fault in the wiring harness between the sensor(s) and the ABS controller. That fault appears to be intermittent, and could be difficult to locate, but if it was found it could look like chafed or worn wires at some point along the harness.

It depends what tests were done in the original diagnosis, but the sensors would have been the first thing to check. If a test showed that it wasn't the sensor, I can imagine that the module would be targetted as the next option, partly due to the difficulty in finding a problem in the wiring harness. It is unfortunate if you paid for a module that you didn't need, but it may still have been cheaper than the labour cost for tracking a wiring fault. I would think that the shop would be participating in some form of policy settlement that gives you a financial break. Whereas they may have replaced something that wasn't faulty, sometimes that is cheaper than doing further diagnosis due to today's high hourly labour rates, particularly for troubleshooting. The fact that they readily gave you the old parts suggests that they aren't trying to hide anything, so talk to them about the next steps, and the costs of what you have done so far. Tell them that you are concerned with the rising cost of this repair, and want to know that you are both in it together. See how that goes.

I don't know the testing procedure for the module, but I wouldn't be swapping them in and out now. I think the cost of doing so, including coding, is more than the value of the module. It may be possible for the module to be bench tested by someone familiar with overhauling them.

[bastereo]

Sounds like its all done and pointless to try and bench test the thing. But like jcl said I would not try to swap them back and forth.

My guess is that you had two issues going in the abs system.
An internal fault code for the abs module and a wheel speed sensor.

Read your paperwork, it should have some answers and the trouble codes and trouble shooting they did.

[Turbo_Bimmer]

Seattleslew, you should try to find an indy with a GT1 to read the BMW codes.
It is possible that you will see errors related to CAN bus (communication bus between modules).

If a module goes bad, or there is corrosion / oxydation on the connector of one 'main' module, the CAN bus can be affected and problems like the one you have can happen.

In the meantime, you could try to disconnect the battery, and spray some contact cleaner in the DME, ABS/DSC, yaw sensor, and the steering angle sensor connectors. Spray and insert/remove many times to rub the oxydation, then make sure to remove all excess cleaner.

I had a similar problem in my E46. The DME connector had contact problems, and I had the tree light intermittently.
Not expensive to try, it may help.