[1fast2liter]

So start car runs. Turn key off and engine stays running. Dash stays on like key is still on. Heater fan shuts off and the air fuel and boost gage shut off. In order to get car to turn off disconnect battery and unplug coils then all shuts off. Reconnect battery and dash comes back on

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[mdjenkins]

A quick search has me thinking fuel pump relay or ignition switch.

Pulling the fuel pump fuse seems like a cleaner/safer way to shut down the engine.

 

[1fast2liter]

Ya but with engine off the dash lights are still on like the ignition is on.. I did order a new ignition switch to see if that cures it

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[DBVeeDB]

do things stay on with the key out? or key inserted but in the off position?

My TT was powering on without the key inserted at all, it was my Fan Control Module back-feeding the ignition power circuit and acting like a key. I tried a new ignition switch, and fuel pump relay first. But ultimately pulling each fuse one-by-one to narrow down the problematic circuit (no obvious codes to guide me in VCDS) was how I found with components to test.

 

[1fast2liter]

How does it back feed? And ignition off key out and car will stay running and dash on like ignition is on. The gouges are hooked up threw the accessories fuse block like block 10. And radio sound goes off but radio itself stays on blower fan goes off for heat but the heat control stays on. No issues at all last time I drove it. Put new battery in car and dash lit up right away

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[mdjenkins]

How it back feeds seems secondary to the troubleshooting method.

 

[1fast2liter]

How it back feeds seems secondary to the troubleshooting method.

What do you mean by Secondary to the trouble shooting method?

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[mdjenkins]

What do you mean by Secondary to the trouble shooting method?

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Which is more important to your situation?

Getting an explanation on how something broke in someone else's car.

Or...

Having a method to isolate the specific circuit in your car that is causing you trouble.

If it was my car, fixing it would be my primary goal. Getting an explanation on how a very specific break is possible would be my second priority.

 

[1fast2liter]

Iam asking how it would back feed cause what he describes dosnt make sense to me. It's a question on how that would work. I will add to my issue the factory Amp turns off with key off too. But radio itself stays on.

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[mdjenkins]

Right...
You're ignoring the proposed method of "pull fuses to isolate the problem circuit" to determine what's wrong with your car.

Instead you're looking for an explanation of how it's possible their car was broken and is now working.

You're like one of those VPs that call into a bridge when the system is down and start pushing for a root cause analysis when everyone is focused on getting back to business as usual. Your understanding of the root cause of a previous incident is unrelated to how you're going to isolate the bad circuit in your car.

 

[1fast2liter]

No i asked how that could be possible. I never said it was what I can do. I bought a new ignition switch to try as that's what the dealer said to try first cause it's what they would try. Iam curious as to how a fan control module would keep a car running if it was bad. Never once did i say I'm gonna go try this. Your assuming things when all I asked for was an explanation as to how that could work

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[1fast2liter]

And never said I wasn't going to pull fuses and see what is causthe problem. But if someone comments in a thread on a question why can't I ask them a ? In return? Maybe I pull all fuses and it does end up that problem. I'd like to know how it's possible. And maybe it isn't my issue. I'd still like to know how it's possible.

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[DBVeeDB]

Power Circuit "15" runs through the relay/FCM module. (you can see the pins are actually labeled with the power circuit labels on the side of the FCM) My best guess is that internally this relay/module failed and this caused what was normally a switched connection, to be constant, which in turn causes my accessories to power up regardless of the ignition switch position. Normally this module would be switched from a signal, but I am guessing that it was forced closed due to malfunction. So I am using the term backfeeding, perhaps incorrectly, but it was causing the Terminal 15 to be powered w/o ignition on.

Pulling the fuse one-by-one, then attaching the battery to see which fuseless circuit prevented the keyless power-up is how I found my next place to check. I then used the diagrams to determine what components were fed from these circuits. It was a few things, like headlight, FCM, a few other relays etc. So I started unplugging each of these components with the fuse back in to see if I could isolate the problem that way. Unplugging the FCM prevented it.... nothing else in the circuit did. Replacing the FCM then also fixed it. There might have been a faster way to diagnose, but after doing the ignition switch, checking all fuses, relays, radio, etc I ended up doing this and found my issue.

Good luck!

 

[mdjenkins]

And never said I wasn't going to pull fuses and see what is causthe problem.

Sorry for the misunderstanding. When you posted more details with no troubleshooting results while questioning the validity of someone else's experience, it seemed you were going off a tangent that would only waste everyone's time.

Instead of suggesting you were asking the wrong questions, I should've just recommended you take it to someone that works on cars for a living.

 

[1fast2liter]

Power Circuit "15" runs through the relay/FCM module. (you can see the pins are actually labeled with the power circuit labels on the side of the FCM) My best guess is that internally this relay/module failed and this caused what was normally a switched connection, to be constant, which in turn causes my accessories to power up regardless of the ignition switch position. Normally this module would be switched from a signal, but I am guessing that it was forced closed due to malfunction. So I am using the term backfeeding, perhaps incorrectly, but it was causing the Terminal 15 to be powered w/o ignition on.

Pulling the fuse one-by-one, then attaching the battery to see which fuseless circuit prevented the keyless power-up is how I found my next place to check. I then used the diagrams to determine what components were fed from these circuits. It was a few things, like headlight, FCM, a few other relays etc. So I started unplugging each of these components with the fuse back in to see if I could isolate the problem that way. Unplugging the FCM prevented it.... nothing else in the circuit did. Replacing the FCM then also fixed it. There might have been a faster way to diagnose, but after doing the ignition switch, checking all fuses, relays, radio, etc I ended up doing this and found my issue.

Good luck!

Interesting. I started pulling fuses but dosnt seem to help. I'm picking up the new ignition switch soon so going to try that. Radio wiring is fine and so is radio. The cold does weird things to my car it seems. Specially if it's not been running for a week or 2. If this does end up being my issue I'll know what I'm looking for too. So thank you for the explanation

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[1fast2liter]

Well wasn't switch. It was the radio. Unplugged the module from the radio and everything went back to normal.

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