Alarm issues after replacing battery - car won't start

[TGreen2584]

I’m trying to replace my 1994 530i’s battery, but when I connect the new one it sets the alarm off and keeps the starter from cranking. Here are a few of the things I’ve tried:

• Making sure that all of the doors, the hood, and the hatch are shut and unlocked
• Pulling fuses 33, 34, 37, and 18
• Turning key to on position before connecting battery
• Emergency start procedure - waiting 15 minutes to reset the code
• Pulling the hidden blue fuse for the anti-theft and OBC

I haven’t been able to locate the anti-theft module, though there is a black 12-pin connector near the battery that isn’t plugged into anything and has three wires cut. The colors seem to match up with the connector to the Alpine alarm module used in the 1993 and 1995 models, which would mean that the three cut wires would correlate to the passenger door, drivers door, and rear door switches. The Bentley wiring diagrams, however, show that 1994 alarm systems are different and didn’t use the Alpine module. I’ve never had issues with the alarm in the past, this all started from trying to replace the battery. Any ideas?

Thanks!

[E38740iMD]

Production date for the 94 e34?

And is it oem or Aftermarket alarm

[TGreen2584]

Production date for the 94 e34?

And is it oem or Aftermarket alarm

Production date is 1993-03-11, and I believe the alarm system is all oem. Haven't come across anything that stands out as aftermarket

[moroza]

• Turning key to on position before connecting battery

Recommend not doing this; ECUs are sensitive and might not take kindly to the brief voltage spike when a battery is connected.

I haven’t been able to locate the anti-theft module, though there is a black 12-pin connector near the battery that isn’t plugged into anything and has three wires cut. The colors seem to match up with the connector to the Alpine alarm module used in the 1993 and 1995 models, which would mean that the three cut wires would correlate to the passenger door, drivers door, and rear door switches. The Bentley wiring diagrams, however, show that 1994 alarm systems are different and didn’t use the Alpine module.

Yours is a very early "1994". Wiring diagrams list it as "SOP 2/93" and aren't entirely correct in some areas (starter wiring, for example). You may well have a 1993 system.

Use these. The system to locate components is slightly clunky, but effective. Your culprit may be either the crash control module (inertia switch under the rear seat and the module itself in the main fusebox) or the "horn relay module", also located under the rear seat and with its own fuse. It's bolted to the back side of the vertical sheetmetal behind the left rear passenger's ankles. May need to loosen the black plastic electronics frame (the one that houses the RM and GM) to reach it. I deleted mine altogether, and spliced two wires (fat red to red/grey/yellow) to keep the OBC working. The Alpine module is allegedly located "below RH side of dash" with no diagram given.