Key Off Engine Still Runs
(Cabriolet C4S) Vin: WP0CA29954S651366
Car came in and when you turn the ignition off the engine keeps running, the dash stays lit as if you had the key in the run position until you pull the key out. Checked all fuses and relays, all ok so went ahead and replaced the ignition switch assembly. No change. Swapped out a lock barrel with another 996 we have here that has a very smooth operating lock barrel / ignition switch yet the issue persisted. Swapped the start lock relay with the DME relay and no change. Can still feel noticeable resistance in when engaging the ignition switch, even with this completely new assembly (probably the lock barrel). When I pull out the lock barrel I can manually turn the ignition from off to run to start with no issues whatsoever. The system is very simple so I cannot imagine what is causing this to happen. Have run through TSBs and done lots of asking around and research to no avail. Curious if anyone has ever seen this before or might have some helpful input. At this point I am ready to order another ignition switch and try it. Thank you.
Yes I have power at terminal 15 with the key in the off position key still in the ignition. Terminal 15 power is cut ONLY when the key is removed. We have swapped out the lock barrel for another known good 996 but no progress. The car has had two ignition switches in it at this point with the same issue.
Since you have power to pun 15, with the key in the switch, and the power goes away once the key is removed, to me, that asks the question, "is the power at pin 15 coming through the switch, or is it being powered from some other place, when the key is in the switch". ? I can think of two ways to find that out. 1, you could hook a current probe around the pun 15 wire and see which direction the current travels when the engine is running with the key in the run position. If you then turned the key off, and the switch contacts opened, you would not have any current flow through the switch. #2 would be to unpin the terminal "P" red/white from the ignition switch plug, and see if the engine would shut off when the key is turned off.
Since I have never worked on a car like this, I can only use a wiring diagram and current flow logic to plot a diagnostic plan.
I appreciate the help. I used my amp clamp and a volt meter simultaneously at the K15 wire and found 1.2 amps and 12v going into the switch with key on. When switching to the key off position I have zero amps and 12v. Key out completely and zero amps and zero volts. I'm assuming power is running into the switch but cannot confirm because my amp clamp does not have an indicator of flow on it (cheap). Im 95% that something is feeding 12V into my k15 circuit. Going to see if the customer wants to continue with this diagnosis and will report back if anything is found. Thanks so much Albin for your help.
Also unpinned the P wire and no change.
Certainly sounds like ignition switch, have you tried just unplugging it.
we replace countless lock assemblies on those. …
Car is fixed. Someone jumped fuse B10 to E1. I can't for the life of me understand the purpose since there is nothing else aftermarket installed and no evidence of aftermarket alarm or remote starter on the vehicle.
Good job. It's incredible how many times a vehicle will come in with what would of been an easy electrical issue, but it then grows into a time consuming ordeal because the owner or friend moved fuses around into spots not usually supported while omitting fuses from their original locations. It can be quite a humbling experience if you let it take you in a wrong direction. BTDT more than once.