ECM question, ignition key [Archive] - Bimmerfest - BMW Forums

: ECM question, ignition key

01-04-2009, 08:38 AM
I have a 1994 525i I bought for my son. The car wouldn't start one day after school, but started immediately for me the next day when I checked it. About 2 days later, I drove it, parked, and when I came back out it would not start (I also did not hear the fuel pump charge).

I pulled the fuel pump out & it tests fine. The fuel pump relay appeared to be faulty, as I could jump the connection & power up the pump & power was present on the the relay control (also verified the ECM relay was functioning as well). The new fuel pump relay would not engage. The wiring diagram indicates the fp relay ground comes directly from the ECM.

I researched a few forums and determined there is at least one sensor problem that can tell the ECM not to start the car (the crankshaft position sensor - apparently if it fails, no fuel or ignition). Is this the only sensor that could prevent the ECM from signaling for start? Will the code reader (from Peake Research perhaps) identify a faulty crankshaft position sensor?

I am trying to find the shortest (and least expensive) route to determine if the ECM is defective or an external sensor. Any help would be appreciated.

Second issue: The ignition key cannot be removed from the column. Anyone have any experience with this? Is it a mechanical issue with the switch itself or could something else be locking it?



01-04-2009, 01:07 PM
a faulty crankshaft position sensor will prevent virtually any car from starting

in regards to the second problem, is the ignition key on a keychain with a lot of other keys/stuff on it? i've heard of this situation where when you hit a bump, the weight of the key + chains will pull the ignition out of allignment

01-04-2009, 01:35 PM
Well, I guess I didn't phrase my question that well. I'm trying to determine if there is a way to test the sensor without a code reader or if there are any other sensors on this model that would produce the same result if bad (in other words, I'm trying to find out if I have a sensor problem or if the ECM itself is defective).

On the ignition question, only the key is present. Thanks!

bimmer dot info
01-05-2009, 07:42 AM
You can test the crank sensor for resistance. It is either 540 ohms or 1280 (numbers are off the top of my head and might be a bit off).