T0RK

996.1 C2 is the vehicle.

I am stumped on this one guys..
-Was driving home, everything working fine then suddenly I got a brief airbag light and lost my radio. Car drove fine the remainder of the drive home. Now car is blowing fuse e1 as soon as I turn the key and the car won’t start. No noise at all when cranking.

- changed ignition switch (still difficult to get key in)
- tried removing the radio harness, still blew the fuse and wouldn’t start.
- all grounds look fine
-clutch switch engages fine
-start/lock relay (#7) in rear relay support was replaced, didn’t work
-no other fuses are blowing
-battery reads 12.8v

-is this an immobilizer issue? Maybe the airbag control module? Car is not a cabriolet and hasn’t had any water damage.

any help appreciated!

dcdrechsel

Any recent work done to the car -radio -Instrument cluster ? Ignition switch replaced after episode ?Key should slide in no effort .Blowing fuses is a dead short good bet pinched wire .Finding it will take a meter wiring diagram and patience.

sasilverbullet

First thing I'd do is replace the ignition switch. The fact that the key is hard to turn points to it. When those things go all kind of weird things can happen with the electrical system.

allcool

I assume when you say "changed ignition switch" you replaced it with a new 1..?

When u say turn the key, does that mean the first position of key in ignition switch blows fuse..?, or do you mean when turning key all the way to try and start car..?

Well, you say the starter is operating and "cranking" the motor over, but not starting...?
If I understand that correctly, then IIRR, the immobilizer is working or it wouldn't crank over.

Did you log any fault codes to start troubleshooting with...?

If not, Might have to isolate your problem of blowing fuses.
Start by finding out exactly what components are protected by fuse E1.

Then individually with fuse removed, one by one disconnect/unplug each component on the circuit and check for a short to ground in the circuit and device, with a MM. Reconnect and move to the next circuit/component/device till you find the short. As others have said, could be in the wiring to components or plugs/connectors, so check the circuit carefully with a MM.

jmo

T0RK

thank you for your help. I replaced the ignition switch with a new one. Fuse E1 is blown as soon as I turn the key from position 0. When I try to crank I get no noise. Could be the battery but the battery showed as healthy.

T0RK

replaced ignition switch with a new unit. Did not help.

T0RK

no previous work done relating to anything other than me replacing the ignition switch. I ordered a Haynes manual but can’t find the wiring diagram at the moment. Do you have a recommended online source for wiring diagrams?

Woodman71

Sheet 16 of this perhaps?

T0RK

thank you! I tested the voltage between pin 1 in fuse E1s slot and ground (0.18v). I then tested the resistance between the 86s pin on the electrical connector for the ignition switch to pin 1 on E1 (9.xx ohms) I’m thinking either the wiring harness for the ignition switch connector needs to be repaired somewhere or the alarm control
unit under the driver’s seat is connected. I’m checking the unit under the seat tomorrow. Hoping for a loose ground or bare wire.

Porschetech3

I would disconnected the alarm control under the seat , then turn the key on and see of fuse E1 blows, if it doesn't, then open up the alarm control unit to see if it is wet /damaged/ burnt..

They can get wet without you even knowing it...

If the fuse E1 still blows with alarm control disconnected, I would locate splice/weld point 85, and separate all circuits, then reconnect them one at a time to see which one is blowing the fuse, then follow that circuit..

jumpy chunky

You should have zero resistance between pin 86s
and fuse E1 in fuse panel. Not sure what 9.xx signifies. Should read 0.00 on meter.
Might have damaged plug connection at ignition switch would be my guess. Or wire is somehow compromised.
you could test by leaving switch connector off and just connect terminal 86s to fuse E1 using a jumper wire. Leave all consumables connected on other side of fuse. Turn ignition to run position.

For safety you should try to disconnect the factory wire at both the connector and fuse panel.leave fuse out initially. Then test for voltage.
Also would be prudent to see voltage at E1 before fuse using factory wiring.

steam_mill

As stupid as this sounds, I had my car towed after I replaced the ignition switch with a new one. I had similar issues (I didn't blow any fuses) to you. Shop replaced my ignition switch again and all was normal again. I wouldn't have believed it tho.

T0RK

just put in a second ignition switch, still no dice. Just pulled the immobilizer, about to open it up

T0RK

I would say the immobilizer appears to be just fine..

dcdrechsel

Porsche tech provided the steps to identify the problem .The fact that the fuse blows when the key is on is verification that the fuse is getting power .The problem is that the load is greater than the7.5 amp fuse. .Likely a short .Don't know your meter but when set to ohms and probes shorted to each other that's a short reading .The output fuse side and car ground probably gives same reading .Using prorsche tech steps fingd the root cause .