[kvuj]

Hello everyone!

I would like to request some help trying to repair my BMW. It recently stopped starting (no crank, though I hear the fuel pump) et I decided to change the starter thinking it was the issue (it was very old and I should have changed it anyway). It turns out that it wasn't the problem because there is still no crank.

Using INPA, I get a few errors including a very unhelpful one (A0B4). I have confirmed that the brake pedal is correctly detected as down in the CAS diagnostics. I recorded a video of me trying to start the car with the voltages values from the CAS diagnostic page.

Is it normal for the voltage HALL12 to flicker?

I am starting to suspect a flaky cable between the relay and the starter.

Battery is very healthy and fully charged (and was paired when installed).

Any help would be welcome


Here are the errors found in INPA:

Errors after clear and start.pdf

Errors before clear.pdf

Errors memory CAS.pdf

[4JawChuck]

See if you can rotate the engine freely.

[kvuj]

Originally Posted by 4JawChuck

See if you can rotate the engine freely.

Interesting, that would be weird, but sure. How would I go about testing the rotation?

I'm guessing you mean the crankshaft or maybe the gear the starter attaches itself to?

[4JawChuck]

Turn the engine clockwise at the crank bolt and see if it turns freely, should turn with a 3/8” ratchet quite easily.

If it takes a breaker bar to turn over you have a more serious issue.

[G35POPPEDMYCHERRY]

need a PHD in electrical engineering to understand bmw electronics hell even crank issues

[4JawChuck]

Simple test is to check that the relay to the starter solenoid is firing, on a 1 series it’s besides the ECU inside the engine compartment box.

If it’s clicking when you crank the issue could also be a failing relay, bad wiring between it and the starter or an engine that cannot be turned with the starter.

[kvuj]

Originally Posted by 4JawChuck

Simple test is to check that the relay to the starter solenoid is firing, on a 1 series it’s besides the ECU inside the engine compartment box.

If it’s clicking when you crank the issue could also be a failing relay, bad wiring between it and the starter or an engine that cannot be turned with the starter.

You mean what contains the fuses on the glove compartment (integrated supply module)? From what I've heard, it's quite expensive and changing it requires reprogramming stuff. Hopefully that won't be it...

Thanks for the help, I'll check this weekend more thoroughly (if the engine turns, if the wiring is not damaged, and if my starter works out of the car).

I've also seen some stuff about the IBS (battery sensor) causing problems, but if the voltage is varying when trying to start, I doubt it would be that.

[4JawChuck]

No, that relay fires another relay, if the second relay (standard off the shelf relay) isn’t firing then you would be looking at the board level relay.

All the first relay does is takes board level voltage (typically 5VDC) and uses that to switch battery voltage to the second relay.

Sorry not familiar with your model of BMW, I had to perform this same test on my 1 series to determine why mine would not start.

Alternatively you can check for voltage at the starter solenoid, on mine I had to remove the intake to do this.

[kvuj]

To anyone who encounters this in the future: it was a bad ground between the engine block and the chassis. The braided cable was extremely oxidized.