Cadillac Repair Questions? Ask a Mechanic for Answers ASAP
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Do the other gear indicators light up if you move it through the gears? Thanks.
The fact that disconnecting battery helps points toward a failing module, most likely the ECM. A module is the only thing that would reset when disconnecting battery. I would recommend trying to remove the 10 amp ECM/TCM fuse to see if that allows vehicle to reset and start, if so I would go ahead and have ECM replaced. Let me know if you have more questions, thanks.
I don't see any other possible causes. The transmission range switch sends signal to ECM to indicate gear position, then ECM sends signal to gear indicator. If removing fuse allows system to reset that pretty much pinpoints problem to ECM. Let me know how it goes or if you have more questions, thanks.
I'm assuming you left key off when you removed fuse?
Next thing I'm going to recommend is removing each fuse one at a time to see if any of them allow vehicle to start. Then depending on which one does we will check to see what module is controlled by that fuse. Let me know, thanks.
I've never seen this before either but I'd still say replace the ECM at this point. Have you tried checking codes during problem? I'm wondering if scantool will even communicate with ECM.
Ya that does make sense which would mean the ECM is failing but the fact it doesn't reset when removing ECM fuse is the odd part. I'll open question up to see if someone else has a better way to verify ECM is problem before replacing.
Try removing the ECM fuse When the ignition is on, i know they say not to, but you said you turn the key on, then, disconnect the battery, its the same thing as pulling the fuse while the ignition is on. Hope that helps. If the ECM fuse pulling doesn't let the car restart, then continue the test as stated above but this time with the key on.
Pull the fuse, wait 1 min, put fuse back in try to start. starts = ECM bad.
Doesn't start = Another Module, like Security, or wireless module that newer cars use to identify the new KEYFOBs.
Hope this makes it easier to make a decision.