pcmhacking.net

Hey guys, Delcowizzid reccomended i ask for assisatance here, im hoping someone could help.

I have a S1 VT 5L manual and have a problem with main power.

Im driving along only when motor is warm, it misses (jerks around for about 1/2 second), all the check lamps illuminate, the needles go down and up and the radio resets. The motor wont stall as its manual.

Some misses are bigger than others and only sometimes the radio resets. (Stock radio with code)

I stop the car and try to lock it but there isnt enough power to run the lock solenoids, the interior light is dim.

After a few minutes of trying it all comes good again instantly i think because its cooled.


I drove around a while with the ABS module disconnected and it still does it. Theres no relay for main power (Only fuses).

Its almost like a dodgy relay the was it just instantly clicks back into action.

I pulled every relay out of the car while taking note of the interior light and it never turned off with any relay being pulled.

Its really got me buggered.

well the interior light is run off the BCM isn't it .... that means you probably need to pull power to the bcm or unplug it before the interior light goes off...

as far as your issue goes ... i'd be checking battery connections, connect to the fuses in the engine bay (the main fuses etc) .....

is it slow to kick over ever ?

the fact things are going dim is telling me there is an issue with power, either a short somewhere or a loose connect or something like that....

if its only when its warm could be something like something is heating up and expanding, once it gets to a certain point its touching on another wire or something like that and making a short.

whats been done to the car recently that may be part of the issue ?

too many unknowns ....

get a multimeter, check battery voltage when its running should be 13.5-14 Volts ....

check it when it plays up ....

work out what terminals power the PCM probe them when its playing up .....

All the terminals are fine, power to the fusebox is fine. Its slow to kick when warm but thats typical of the 5L starter as it gets hot on the manifold.

The charge is ok when cool at 14v but when hot and all power running like lights and a/c it can go down to 13v maybe even 12.5v. Bad design there as the fan blows directly on all the battery & main wiring...

Nothing has been touched on the car lately and is completely stock.

I just dont get how there isnt an ignition relay. If there was then for sure it would be that. The symptoms dont fit a loose wire. Everyting would tend to flicker if it was a loose wire. This problem is like a mechanical/electrical problem much like how a relay works.

I've heard of similar problems with some of the V6's.
I'd have a good look at the positive wire routing from the alternator to the battery, if this shorts when hot you will get the same symptoms you describe with evrything going dead.
As this wire snakes around a bit, with time it can chafe and short out, whatever problem you have if it is wiping out the radio as well all power to the vehicle is going.
Bit of a long shot , but also feel along the wire for any breaks inside the insulation, if you find one it will be fairly obvious.
Also check the fuses in the fusible link near the battery, there should be 2 x 50 Amp fuses from memory.
You may want to have a look at the justcommodores website, as they have more information on general vehicle trouble shooting.

Good Luck

ide be looking at the alternator first after you described the voltages its most likely got hot tooo many times and has some issues maybe find one to borrow for a few hours as a test

check the terminals again, you have a bad connection somewhere.
there is an earth point on the rh inner guard
.
the way it comes good suddenly indicates a loose main power or ground

Rob

Ok cheers guys, i'll have a good look over the weekend. I'll let you know.

Hey Bob hows my memcals going?

Luke.

should be in the mail on monday Luke, been flat out

No probs, i thought you may have been.

Well i went right through it today, tracked down where all the earths went and all were tight and clean. Everything else is tight and clean too.

Fuse box seems fine.

I noticed today when i was mucking around that when the car is hot its slow to crank. I started it, let it idle for a while, turned it off then started it again in a matter of seconds and it cranks fine. When i leave it for a few minutes then its slow to crank. Its much the same as my other car where ive moved the battery to the boot and used too smaller cable. Does the exact same thing as the VT!

I wonder is it heat soak in the wiring and building resistance? Doesnt really exlplain why i only get like 5v when the problem happens.

Then again why when im driving the power only cuts for a split second but when the motor is stopped the low voltage stays for about 5mins?