Earlier this summer, and in fact starting in the late spring, a bunch of warning lights popped up on my car out of nowhere. A quick scan with my bootleg copy of Rheingold ISTA showed me there was poor/erroneous signal coming from the right rear wheel speed sensor. I couldn’t clear the code, which led me to believe there was probably an open circuit somewhere, even though no trouble codes from the car explicitly said that.
I started by swapping the rear wheel speed sensors from left to right and vice versa, hoping that the problem would be a cheap and easy to fix sensor. Unfortunately, that was not the case. I wanted to check the tone ring for the sensor next, despite it being unlikely that a damaged tone ring would cause an unclearable code.
On this car, a 2008 BMW 535xi, the tone ring is built into the wheel bearing, and you can’t see it without taking the axle out of the bearing. I knew it would be some work to get everything apart enough to look at the tone ring, so I figured for $50 or so, I might as well replace the bearing while I was there. I watched a couple videos on removing the bearing from the car, but I think all of the featured cars were automatics, and mine is manual (fairly rare in an E60). You would think that wouldn’t have anything to do with the rear axle and wheel bearing. You’d be wrong. On the manual cars, the axle is an extremely tight fit into the hub of the bearing. Every other car I’ve worked on, the fit has been tight, but loose enough to push the axle in and out by hand if it’s new and lubed up. On the manual E60s, it’s so tight I had to buy a puller to rip the bearing out of the spindle. There’s probably a special tool to install the axle, but I don’t have one, so I slammed it into the concrete floor of my driveway a few times. This whole thing turned into a multi-week saga because of the weather, waiting for parts multiple times and my constantly fluctuating levels of motivation. My car was on jack stands in the driveway for about three weeks. And at the end of it, I didn’t fix anything. The lights were still on. If I knew how huge a pain this job would be I wouldn’t have done it. On the other hand, now that I’ve done it once, I could do it much quicker in the future.
Next, I decided I wasn’t interested in fixing the car myself. I tried a used ABS module because it was cheap and quick. This didn’t fix anything either. I knew there was likely an open circuit between the right rear wheel speed sensor and the ABS module, but I thought that I didn’t have the right tool to probe the tiny pins on the electrical connectors, and I didn’t want to run new wires down the length of the car. The shop I took the car to seemed more interested in fixing minor or nonexistent problems than diagnosing and repairing the ABS problem. So that was $100 and change down the drain.
I finally got around to diagnosing the problem myself with some help from some male to male jumper wires for hobby electronics. It turned out they’re just the right size to fit into the tiny pins on the electrical connectors. I quickly discovered an open circuit on one of the wires going from the sensor to the ABS module. Yesterday, I finally got around to replacing the wire, and it fixed my problem. At first, on the ABS light was extinguished, but after quickly calibrating the yaw rate sensor, they all disappeared. I took the car for a test drive, and everything seems normal now. The next step is to get a fresh inspection sticker for the car, and then hopefully I’m done with fixing it for a while. I do want to do an all wheel drive service, which I have the fluids for, but I really need a lift for it. I’ll have to see if my friend with the shop could lend me some lift time for it.