2003 325ci - engine will not power down..tail lights and dash cluster on

[pagz]

My daughters engine will not power down. When ignition key is in off position, car stays running, dash lights and tail lights are on as well. I'm having to disconnect battery to kill power and stalling it for car to shut down. I've replaced ignition switch with OEM, did not correct. I cleaned all battery terminals and body ground cable as well, car ran flawless for 4 weeks with no problems and now problem is back. Looking for thoughts and any ideas as this will be my Saturday project. Thanks for your time!

[MarcoZandrini]

The first step in diagnosing a problem is to scan the engine computer and the automatic transmission computer for codes. Yes, I realize the problem doesn’t seem related to the computers, but in reality it is. The only way that engine runs is if the computer is telling it to run. Without the computer the engine is a lump of aluminum. Scan to see what comes up. Report back the codes.

[johnjmurray]

There was a recall for faulty ground wiring in the tail lights. They pop right out from the trunk. There is a catch-tab on the outside edge. I don't think this can get bad enough to mess with the engine but who knows...

[jclausen]

We had a car recently and the iPod adaptor wiring was plugged in to the CD player wiring and it was doing alsorts of strange thnings and we could not communicate with the buss, unplugged the iPod wiring, fixed. And this wiring had been in the car for quite sometime, it was not installed recently

[pagz]

Thank you Marco, johnjmurray and jclausen for replying. A friend told me this a long while ago "KISS", (keep it stupid simple). Looking in the trunk area I noticed some speaker wire hanging, with bare wire ends that I previously ignored. My son had installed and later removed some boom box speaker system. Both wire ends were now touching. I traced one of the wires to the 250 amp fuse box in the trunk, the other wire was splice to a relay close by. I did not look closely as to what pin on relay. I cut everything out and voila, all good to go, kids!

[MarcoZandrini]

Great sleuthing.