ABS, TCS, and Auto Tranny related?

[winters97E39]

Recently purchased a 1997 528i a few weeks ago with 120K miles. The previous owner had the ABS system totally replaced in January. Recently my ABS and TCS lights have come on following backing out of the driveway (which requires turning the wheel) It goes off again the next time I stop somewhere, backout, and go forward again. I can consistently make it do this. I stopped by my friend's shop and he confirmed a code was being thrown for the front left wheel speed sensor. At the same time this is happening (ABS & TCS lights are on) the tranny seems to want to stay in lower gears and not upshift. I can make it upshift by shifting into S3, then back to D. Are these related in someway? Is the bad wheel sensor sending some kind of funky data to the tranny to not let it shift correctly? I am going to scope out the sensor when I get home today, make sure the wire is not stretched or loose, but was just curious about the relationship between the three. Thanks for any help

[winters97E39]

anyone?

well, this afternoon the ABS and TCS light stayed on. Pretty much the only way it will shift is if I do it manually from 1 to 2 to 3 to D. Havent had a chance to checkout the sensor yet, waiting for kids to go to bed. Since I am going out of town tomorrow, this may have to wait until the weekend.

[Dirty_Tool]

Could be related.. Make sure that all the tires are the exact same size. if 1 or more is different than the rest this will cause this to happen.

[winters97E39]

yep, all tires are same size. just got back from the test ride... all is well. I took the wheel off, and then removed the abs sensor wire. gave it a thorough cleaning and plugged it all back up nice and tight. made sure there was enough slack in the wire. When I started the car, the abs and tcs lights were still on. I proceeded to back out of my driveway, and and soon as I shifted in to D and moved forward about 5 feet, both lights went off and it shifted as smooth as glass through all the gears. woooohooo! my first bimmer fix!!... I'm guessing when I had it at my buddy's shop and we were inspecting a suspect brake pad sensor, we must have inadvertantly loosened up the abs sensor wire in the process, or pulled a little slack from it where it would cause it to stretch too far and cause a fault. Anyway, I'm very releived its not a major issue... although if I had to replace the sensor, I can get one for like $60 anyway, so that wasnt so big a deal.

[winters97E39]

well, dammit, it came back again this morning, but the shifting issue wasnt there. the lights came on, and just like before, when I stopped and backed out of a parking space and went forward, they went off again. Looks like I will need to take the brakes off to inspect the contact surface, or get a new sensor. Off to NYC today, so will update when I get back later next week.

[winters97E39]

check out what I found searching the net today:


Question: 1994 BMW 840Ci 4000 mileage: 83,000. Hi, I'm the unfortunate owner of a BMW 840Ci, with an ABS problem. On starting the engine the ABS carries out its usual test and both the traction control and ABS lights go out. As the vehicle accelerates away and reaches above 5mph, both lights immediately illuminate and stay on. The fault can sometimes be cleared by switching off the engine, restarting the engine and then counting to 30 before engaging reverse, then reverse the car with full left hand lock on the steering wheel! The car will then drive away normally without either of the ABS lights illuminating. If however either of the rear wheels are spun, i.e. on gravel, then both lights will immediately illuminate and stay on. The car has been into the local BMW dealership for diagnostic checking, where they informed me that the pump relay was faulty. This has been replaced to no avail (and also the memory reset). They are now talking of requiring to test the car further for up to a day, at £85 per hour, just to find the fault! Prior to sending in the car initially, I removed all four wheel sensors and checked each of their resistances, which were all comparable. Although one on the left rear was found slightly bent due to stone damage, it was easily straightened. All four wheel segment rings were also cleaned up and in good condition. Any positive advice of tests that I could carry out would be greatly appreciated, before breaking the bank. Thanks in anticipation.

Answer: Your problem probably lies in one of the four wheel sensors for the ABS. There is a better test than the resistance check you tried. Unplug each of the wheel sensors. Spin the wheel segment rings and check for AC voltage at the sensors. You should have between 1 to 3 volts AC if the system is operating properly. Also check to see if you have a slightly loose wheel bearing that is allowing the segment ring to contact the wheel sensor.

http://www.2carpros.com/makes/bmw/840.htm



The problem described is almost exactly what I am seeing on my 528.. I will check out the front left sensor and segment ring this weekend and tell you what I find.......

[partsden]

I had the exact same problems and It started happening at the same times yours backing out of my driveway and like you said it got as bad as having to manually shift, so anyway I had my car scanned and it came up as a right wheel speed sensor, so we tried cleaning it and same story as yours went away and came back so I gave in and bought one to replace it but as we put it up I noticed there was play in the wheel bearing figuring that we replaced the wheel bearing it all went away and smooth sailing from there

[winters97E39]

Cool... thanks for the confirmation. I had my buddy order me a new sensor and will check out the hub this weekend.

[winters97E39]

Replaced the ABS sensor this evening after work. All issues are gone, ACS and ABS lights went out, car shifts smoothly through all gears..

thanks everyone for the help!

[winters97E39]

update... everything still working fine after the ABS sensor replacement...