05-26-09, 01:30 PM
HELP! The start button on my 05 STS fell off yesterday and I couldn't get the car to shut off; took it to a dealer and they finally disconnected the battery cables. Their scanner said something might be amiss with either the PMM, IPM, or BCM. The car is now "stuck" in accessory mode even when the battery cables are disconnected, touched together, and reconnected, and the ignition button assembly is unplugged. In other words, the car thinks it's constantly in accessory mode, and I can't start it even with the remote start and the entire ignition switch/button assembly no longer works.. Any suggestions as to what to do/try/mess with before I spend several hundred on one or more of the above modules? Comments, etc. are much appreciated. Thanks, Jeff.
Step 1 - Replace the ignition switch.
Step 2 - Battery cables reset trick.
Step 3 - Read codes & start swapping/troubleshooting(?)
Did the old switch break, crack or wear out? If so, it may have taken out upstream modules. Test it for short circuits.
If there's no evidence of switch failure, perhaps a bad module cooked the switch contacts.
Another thing that can cause the same problem is a bad abs module/pump. It's probably not the case here but it happened to me and one other guy on here.
05-28-09, 10:06 PM
Thanks for the advice. My new switch should arrive in a few days; hopefully that solves the problem. In the meantime however, I'd appreciate an explanation as to what the BCM, IPM, and PMM (power mode master?) modules do. Based on your knowledge, which do you THINK may need to be replaced and why? Their scanner may give me a more direct answer, but I'd be interested to hear someone else's opinion. Thanks again.