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Angel Martinez
Angel Martinez,
Category: Cadillac
Satisfied Customers: 60
Experience:  Lead Technician at Tire Kingdom Auto Care
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Cadillac CTS Wont Start As Park Indicator Not Lit.

Customer Question

2005 Cadillac CTS won't start because the park indicator isn't lit up. If I leave the key on unhook the pos battery terminal and then reconnect once I hear a buzzing at the ECM then starts. I replaced TCM but no change.
What can I do?
Submitted: 8 months ago.
Category: Cadillac
Expert:  Dan replied 8 months ago.

Hello, my name is ***** ***** I'm here to help get your problem solved.

Expert:  Dan replied 8 months ago.

Do the other gear indicators light up if you move it through the gears? Thanks.

Customer: replied 8 months ago.
No none light up till I do the thing with the battery terminal. Then car works codes..shut it off for five mins or so and same issue
Expert:  Dan replied 8 months ago.

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.

Customer: replied 8 months ago.
I replaced the TCM but not ecm. The only issue I have with that solution is it will restart fine as many times as I want until I shut it off for five or ten mins
Expert:  Dan replied 8 months ago.

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.

Customer: replied 8 months ago.
Removing the fuse did nothing car would not start without it. I put it back in and it did not reset till I turned key on unhooked battery cable and reattached once ecm starts whirring
Expert:  Dan replied 8 months ago.

I'm assuming you left key off when you removed fuse?

Customer: replied 8 months ago.
Key was off
Expert:  Dan replied 8 months ago.

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.

Customer: replied 8 months ago.
Tried every one. Would not start with any of them pulled. From all I've read on the problem is that it loses memory of being in park after the time period goes by. The only way to start this car is by how I've said. I was hoping to find the solution rather than just throwing parts at it ...I am a mechanic this is just something I've never experienced before.
Expert:  Dan replied 8 months ago.

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.

Customer: replied 8 months ago.
Yeah it's a really weird one. Scan tool works..just tried it. So scanned when it had the problem showed 0 codes and all moniters start..wouldn't expect all moniters to be set at that point. Then I did the battery disconnect thing to start still o codes but had 4 moniters unset. This has got to be the ecm losing memory of shift position? Does that make sense to you?
Expert:  Dan replied 8 months ago.

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.

Customer: replied 8 months ago.
Ok thanks. I have no problem replacing ecm it's just i replaced TCM and didn't want to just waste the money but I'd love to get this problem solved. Thanks alot and let me know so I can order it and have by the end of the week
Expert:  Angel Martinez replied 8 months ago.

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.

Customer: replied 8 months ago.
Hey ok so put ecm in and got my park indicator light back. Car won't start. Do I have to get this ecm reprogrammed at the dealership or is there a way I can do it. I am a mechanic just don't have access to gm computer stuff