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OEM Bimmer Parts

Subject: Here's a tidbit for ya.
Author: Gcracker : member since May, 2004 : 263 posts
Posted on: 2005-11-21 21:26:47      
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I work at a Saab-specific repair shop in Portland, Me. The most common ELECTRICAL faults are as follows:
1. Bad sensors (Inconsistant resistance)
2. Open loop sensors (No continuity)
3. Bad system/pump relays
4. Bad ground
5. Bad ECU

That's the list in order of frequency. The thing that happens most is that you test all four wheels and get the same result at a speed of one revolution per second. About 100mVac. BUT, when you test for resistance, you either get a solid value way out of spec, or a steadily increasing value (capacitance).

For example, a '94 9000 will light the ABS light. I remove the ecu and test for the sensors at the harness connector with the car in the air. When spinning all the wheels, I get Vac, but the expected resistance is 1025 Ohm, and instead it will be 22.4kOhm, steadily increasing in resistance, just like a battery charging. I'm not sure why iot happens, but when impulse-type sensors go bad, sometimes they act like a battery and actually store charge.

So don't assume the sensor is good just because it sends an AC waveform.

BTW, my '86 528 did the same thiing and it was a missing tooth on the rear impulse-rings. I ended up replacing both hubs and fixed that problem. ('course I wound up with some new ones, but that's a different story)

'88 M5 193k (Engine out)
'87 528e 211k "is" package (falling apart)






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