VP security off, but engine immobilized!

[Glenn Littleford]

Hi guys.

Got a weird intermittent fault. The other day I went to move the Vp V6 ute after a week, and it would not start. The fuel pump didnt even prime, and no engine light. It would crank over, and if I cranked it for long enough the fuel pump would prime, as expected via the oil pressure switch.
I shorted the AB test points on the diagnostic plug and turned on the ign. The engine fan should have started, it didn't, and no flashing engine light. I tested for power at the ECU, all good, and the engine light also tested ok.
I suspected the ECU had died, so swapped it with a known good one. Same deal, nothing.
I then wondered if the engine immobiliser was some how on, even though its turned off at the key switch passenger A pillar. I turned it back on with the security key, the red LED started flashing, I used the FOB to turn that off, turned on the ignition and I could hear the pump prime. The car started.

So was the engine immobilised, even though the immobiliser was disabled? I turned the immobiliser key switch off, but the car now starts up as normal, so the fault has gone away $*#$%!!!!!

Does it sound like a immobiliser issue? If immobilised, will the ECU behave that way, ie, no diagnostic lights? I do drive down some rough rural roads, maybe there is something loose.

I had a similar issue a month back, where I drove the car out onto the street, but it just died, and I had to push it home. Next day when I went to find the problem, its started first kick.

Glenn

 

[MikeC]

"I then wondered if the engine immobiliser was some how on, even though its turned off at the key switch passenger A pillar. I turned it back on with the security key, the red LED started flashing, I used the FOB to turn that off, turned on the ignition and I could hear the pump prime. The car started."
I have a car with an aftermarket security system that does this after I store it in the shed with the battery disconnected. Are you sure your battery leads are good?

 

[delcowizzid]

The zadi key in the door shut gets corroded contacts and stop making a good connection a wiggle quite often gets them going for a while you can join the 2 pink wires behind it

 

[Glenn Littleford]

Yeah I'm starting to suspect that switch. How easy is it to get to, with big man hands?

 

[delcowizzid]

If it still has the security plate over the ecu in the passenger side kick panel you will have to drill out or grind off the super hard rivets holding it in to get the ecu out of the way then you should be able to get at the wires

 

[Glenn Littleford]

Yeah removed the ECU as part of the testing. No access to the back of the key switch, though there is a hole to let you access the back of the door light switch. I suspect the wires to the key switch go up inside the pillar and out way above the glove box somewhere, no easy access, and dont want to pull the dash out.

I did work out if you short a wire on the ALDL connector to a wire on the ECU ( I wont mention the wires, its a security system after all ), you are effectively bypassing one contact on the key switch and the car should start, though the immobiliser will be beeping at you if the key switch is still on. So I might put a hidden switch on this, that way if the car wont start or just randomly dies, I can quickly bypass the immobiliser and see if that's the problem.

I would like to fix the key switch itself though, but I suspect access to it would involve ripping half the car apart.

Glenn