BMW E46 Electrical Problem

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A friend of mine has an electrical problem with his E46, and it's stumped his mechanic.

His car wouldn't start, couldn't be jumped, so he had it towed to a shop. His mechanic first thought the starter was bad, then later said no, it's seems to be the neutral safety switch. It doesn't seem to be that now either. The latest info is that the car keeps blowing number 30 or 32 fuse. The other pertinent info, I think, it that the car's battery warning light came on a day or so before the starting problem?

Any ideas?
 
How old is the battery? What is it showing for voltage? BMW electrical systems are very sensitive to battery voltage. Also check the condition of battery cables and all connections. The battery warning light coming on might be a good place to start.
 
Originally Posted By: Trav
Sure, how about some accurate vehicle information not just E46.


It's a 2002 325i.
 
Test the alternator exciter circuit.

If the battery light bulb fails on my Volvo 240 instrument cluster, the exciter circuit will open, and the alternator will not charge.

Just throwing the suggestion out there just in case the mechanic has not thought about it.
 
Make sure the battery is fully charged and in good condition before doing anything. It does have a relay down in front of the drivers front fender, it could also be a bad ignition switch, bad ground, shorted wire, corroded connector, etc.
Fuse 30 and 32 are engine control.
Diagnosing the starter circuit is easy enough for any mechanic its pretty basic stuff.
 
Thanks for the tips; I'll pass them along. Mechanic says the battery is okay.
 
Like Trav said, charge the battery up full with a battery charger before working further. Battery light coming on usually means the charging system isn't working. It is possible that the battery has just run down until the car will not start. Jump starting doesn't always work in that situation.
 
Here is the latest from the mechanic:

"Fully charged, fuse 30 keeps blowing, 32 is good, ground is good. I can trick the car to get it started. The shift readout on dash displays (S) all the time; it doesn't show P,R,N,D etc like it should. Until we solve that, we're stuck."
 
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Mechanic still is stumped. Transmission is stuck in sport mode.
 
It sounds like a connector is corroded or a wire rubbed through. just guessing, without having it I have no idea but that where I would start testing that circuit.
A FSM and wiring diagram are a must otherwise your dancing in the dark and hoping for the best.
 
The key is the circuit for fuse 30; trace that circuit and fix the short. The no-start/Sport mode issue can virtually always be traced back to that circuit.
 
Originally Posted By: Trav
It sounds like a connector is corroded or a wire rubbed through. just guessing, without having it I have no idea but that where I would start testing that circuit.
A FSM and wiring diagram are a must otherwise your dancing in the dark and hoping for the best.


Trav, is a FSM a field strength meter?
 
fsm=factory service manual.
i would look at the transmission harness and tcm first.
Trav is spot on.there is a short and the tranny is indicating a mode you didnt select.its your smoking gun.
 
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