Holden VT electrical monster, not a gremlin but a monster

[Gunner]

Not sure if its the right area to post this, but all you fellas are really clever so I hope you can help. I am a qualified mechanic, with 10 yrs on the job, but never seen this. I hope someone can help.



Jumped in my vt last night to go to servo, started fine, drove fine, turned it off went into servo for 2mins, came out and car wouldn't start. Acting as though had a loose batt terminal. Checked that and all was fine, went to start again same thing, throws starter solenoid, but wont turn over. In addition to this, noticed fuel pump relay tripping out, dash lights were very dim, but came back after about 30 seconds. Swapped relays out, checked fuses, no change.

Had a mate come down with jump pack, hooked it up, and same thing, removed starter trigger, and tried to trigger manually, it didn't want to turn engine over, persisted till managed to get it to turn over, drove car home, headlights, dash lights, door locks, everything operational. Left it for the night.

today, tried to start it the same way, and couldn't get it to start, so proceeded doing the following....


Added 5 new ground straps and cleaned originals (no change)
Cleaned batt terminals, then replaced batt terminals
Charged battery
Bench tested starter (seems ok)
Did current draw test (inconclusive, sometimes 2v drop at starter motor, sometime 8v drop, sometimes no drop)

but there was no changes what so ever, and I still have the following issues

Headlights short out (flick on, and turn off immediately, regardless of key position, but with reds on seems to trigger indicators aswell, yet to test indicators)
wipers short out (relays triggers, start to move, and turns off)
dash goes dim after tyring to start (via key and manually)
abs module trips (relay inside going off for about 30sec, 2 clicks per sec)
fuel pump relay trips (seems to be related to dash lights, clicking stops, dash lights are back, so pulled FP relay, still does it)
starter will not turn engine over (even via manual trigger) just throws solenoid and shorts everything out

Removed starter relay, fuel pump relay, and engine cont. relay (assuming engine control/ecm/ecu relay) disconnected abs module, and headlights stay on, till I manually trigger starter.

So I have come to the conclusion I have a short in the starter, or in the main power to starter. But why have I not blown 1 fuse, in any circuit? Or has the BCM shit itself?

Driving me nuts, never seen anything like it, I just want it fixed so I can sell it.

Anyone have any ideas?

[Gunner]

Forgot to add this is all stock, factory memcal, etc haven't touched anything, haven't had an issue till this.

[The1]

does definitely sound like possible BCM faulty

[Gunner]

If I do the mod to disconnect it, as you would to tune in real time, would I be able to start it?

I have a smashed vt, if I swapped out the bcm, and ecm and used the keys from that car, would that work?

Unfortunately I specialise in jap performance cars, so the way this holden is put together is foreign to me.

Also only throws code 12, which is everything operational, so I dunno about bcm, cause wont that throw a code?

[The1]

sounds like your only checking pcm fault codes

Turning vats off in the tune will only stop the ecu waiting for bcm data to enable the injectors

Best idea is to swap bcm and pcm and keys

[Gunner]

Will give that a go tomorrow, just need to find a way to get to the other car.

Thanks for your help mate.

[vlad01]

in what way does it not turn, start or actually the crack not physically turning like the engine is seized?

if the latter try turning the crack with a spanner to see if it actually turns. its it doesn't it may have hydro lock or similar

[Gunner]

It throws the starter solenoid, and shorts out. Engine still turns over by hand.

[Gunner]

Well the car is starting via a jump pack again, although it struggles.

in park, and free revving over 4000rpm, results in the speedo going to 20km and a random beep from the dash, followed by low traction light, and abs triggering (can feel it in the pedal) anyone seem that before?

yet to get to my spare car, so haven't swapped the bcm yet.

[VL400]

A dead or failing ABS module can make the dash turn in to a xmas tree.

Am not sure if the lack of or slow cranking is another symptom though.