Need help asap car won't start after head unit swap

[velj]

Fuses in footwell Re fine

[doubledip]

how are u testing the fuses? pulling them completely out to look? measuring boith sides to see if power? how?

[velj]

Taking each one out and checking if they are blown, each one u can see a solid connection none are blown none are burnt or anything

[foxdie]

There's no messages on the dashboard?

I've found that if the LSCAN line that goes into the head units is grounded or misconnected, it effectively immobilises the car because the security ECU cannot communicate with any other system.

Try unplugging the head unit completely and seeing if your car starts then.

[velj]

Where is the lscan line?
Both head units worked one I put in and now I jsr put the old one back in it,
It came up with abs fault then came up with contact dealer! I jst don't understand how changing a headunit fucked the car

[foxdie]

Where is the lscan line?

On my VXR8 (Clubby E1, directly compatible with VE) it's the pin 6 (green wire) on connector X4. LSCAN is just what us devs call it, it's the Low Speed GMLAN network.

Both head units worked one I put in and now I jsr put the old one back in it,
It came up with abs fault then came up with contact dealer! I jst don't understand how changing a headunit fucked the car

Well, the head unit may work with the ignition off, but as soon as you turn it on it'll try and obtain security information from the BCM ECU (VIN transmitted over LSCAN) and say "security lockout enabled" if the VIN doesn't match, however this shouldn't stop the car from starting unless there's a short or fault.

The fact the ABS ECU is also whinging also suggests that something has fouled LSCAN, but these ECUs sometimes need time to reset (as they need to fully power down, some don't for anything up to 60 minutes).

Try putting your old head unit back in, wait 1 hour with the ignition off / key out, then try again.

[doubledip]

This sorted ? If so what what was it ?

[velj]

All fixed
I didn't get a second of sleep that night, next day auto elec came the battery had 12v power but had like 3v crank so wasn't enough! Just a bad coincidence fml haha

[radrace19]

I was going to post dead battery but didn't submit it lol
Glad you found the problem

[silversv6]

Most people only check the battery for volts, not cranking amps & always leads them to other avenues & a big massive headache. Some cars will not even try to crank if the current is below a certain voltage. Always try jump starting it first before you stress out and have a heart attack. Batteries can hold the volts but bugger all amps. The easiest way to check your battery is turn on the headlights & crank the car over & if the lights dim severly or go out, then the battery is normally screwed. I have found that older batteries (2-3 years+) can be fine but one cold night can ruin them, just like that!