VX commodore starts sometimes

[Immortality]

Looking at the wiring diagram,

+12 volts comes to the starter relay via the ignition switch. If the 12 volts is missing at the relay (pin 85) than the problem lies between the relay and the battery and is most likely the ignition switch. Pin 86 is the earth side of the relay which runs through the Neutral safety switch to the PCM (security system/VATS). You would need to test this circuit for continuity to ground. Or the relay itself is the problem?

 

[HoldenHoon]

Looking at the wiring diagram,
View attachment 259004
+12 volts comes to the starter relay via the ignition switch. If the 12 volts is missing at the relay (pin 85) than the problem lies between the relay and the battery and is most likely the ignition switch. Pin 86 is the earth side of the relay which runs through the Neutral safety switch to the PCM (security system/VATS). You would need to test this circuit for continuity to ground. Or the relay itself is the problem?

Sorry mate didn’t get any notifications so i didn’t bother to check up on the thread. I’ve just bought a new ignition switch and I’ll chuck it in tonight and let everyone know how it went. Fingers crossed

 

[HoldenHoon]

Just a reminder for everyone. These are the new/changed parts that I’ve done so far for this problem.

New starter motor
New start relay
Cleaned out nss contacts with cleaner and a pick
Cleaned up motor grounds
Tested key battery - good
Key is making contact on the key reader
Checked for blown or faulty fuses. Couldn’t find any.
Tried locking/unlocking doors. Also checked if the immobiliser is activating randomly which it wasn’t.

 

[HoldenHoon]

Looking at the wiring diagram,
View attachment 259004
+12 volts comes to the starter relay via the ignition switch. If the 12 volts is missing at the relay (pin 85) than the problem lies between the relay and the battery and is most likely the ignition switch. Pin 86 is the earth side of the relay which runs through the Neutral safety switch to the PCM (security system/VATS). You would need to test this circuit for continuity to ground. Or the relay itself is the problem?

Just changed the ignition switch and still the same thing. It only does it when the car is warm. So I was thinking maybe CAS? Or possibly DFI as this module speaks to the ecu apparently.

 

[Immortality]

A faulty CAS/DFI won't stop the engine turning over, it just won't fire.

If it only does it when hot then something is going open circuit (with heat). It's going to be time to start testing circuits with a multimeter and see where the signal is lost.

 

[HoldenHoon]

A faulty CAS/DFI won't stop the engine turning over, it just won't fire.

If it only does it when hot then something is going open circuit (with heat). It's going to be time to start testing circuits with a multimeter and see where the signal is lost.

When I checked the start relay pinning with a multimeter. It showed that I was getting -12.84 Volts to the starter motor relay when it was working. When it didn’t want to start it would go to 0. No immobiliser nothing. When hot wired it starts and runs.

 

[Immortality]

Then you will have to work backwards through that circuit to find where it's loosing the 12 volts.

 

[HoldenHoon]

Then you will have to work backwards through that circuit to find where it's loosing the 12 volts.

Yeah I will have to. The pin that it’s losing power to is linked to the ECU and NSS. Doubt it could be the ECU though.

 

[Lex]

Yeah I will have to. The pin that it’s losing power to is linked to the ECU and NSS. Doubt it could be the ECU though.

What about the wires between the nss & the ecu?

 

[Immortality]

How are you testing for 12 volts at the relay?