Another mystery

[FX Panelvan]

G'day All

I have a new problem that has me stumped. I know it is difficult to diagnose from afar but any suggestions will be helpful. As to what I can check.
The problem is this in brief. My Chev has Commodore SS motor (LS3) and Jaguar front and rear suspension. It has been trouble free for quite some time until last week.
I took it out down to the beachfront one night no problem. Come time to head home, No headlights??
Came home anyway without incident. Left it to look at in the morning.
Next day went out and no start??? .
Fixed the headlights okay, A bad connection fixed easily.
But no crank, found another bad connection. Think it was just corrosion on the relay contacts. Salty enviroment does not help.
Still no start, cranks fine but no power to ECU.
I have checked everything I can think of would appreciate any thoughts / suggestions.

[Gojeep]

Check the ground wire for the ecu, it will give you a problem like this. Otherwise make sure there is no corrosion even in the fuse box etc.

[zuffen]

Buy a scanner and see what it tells you.

I have one in my Glovebox in the Fargo, LS3 powered.

It's surprising how often I use it on other cars in the family.

My wife's (dog mobile) a 2019 Caddy had a clock spring failure last week and I scanned the ECU to see any fault codes. I've scanned my Mercedes, my sons Evo and the other son's RX8 (thankfully sold) and a few friends vehicles.

Cheap and worthwhile with modern cars in the family.

Once you get a code go to Google and it will most likely tell you what's wrong.

A few month's ago, coming back from cars and coffee with Sly Fox the Fargo went into limp mode a couple of K's form home. A scan tells me it had an issue with a sensor and I could track it down and for $50.00 I purchased a new oil pressure sensor and the pile of pooh ran again.

Seriously a good investment and a decent one is under $100.00. You can also erase a lot of fault codes with one.

[FX Panelvan]

Rod

Thanks for the reply. I read that one about an earth to the ECU.
Not sure if there is one. Should it be on the actual case?
What baffles me is that the Ute was running fine when I came home. Next morning nothing??
And now still nothing after much head scratching and bad language.
I will try the scanner though not sure there is power to the plug in point.
Something to look at though I have almost given up.

[Gojeep]

On my ECU the fault was the earth and was just a wire out of the harness from the ECU and grounded right near it. None on the body of the ECU itself.

[zuffen]

LS3 is the same as Marcus described.

Have you confirmed you have power going through the neutral start switch to the start relay that activates the starter solenoid.

I'd do old fashioned fault testing from the starter back as that's easy enough and doesn't delve into the ECU.

I find the problems with EFI tend to be external to the ECU and usually end up being a chaffed wife either shorting out or breaking.

[jeffa]

In the first post you mentioned beachfront, and two cases of bad connections/corrosion....
I know where I'd be starting.

" Still no start, cranks fine but no power to ECU."
Do you have a wiring diagram? No power to the ECU should be fairly easy to sus.

[Sudsy]

You need constant battery voltage (2 orange wires) and ignition voltage (2 pink wires) Blue plug pin 1 and 40 are ground. Pin 19 is ign and 57 is Batt+.
Red conn pin 1 and 40 are ground. Try and back probe with a mutimeter. If you don't have the power and grounds you have to trace back to the power source and find the problem. If it's cranking over you can forget your neutral start switch as that is ok. I would check for a ign relay maybe.

[FX Panelvan]

Thanks all for the replies.
I finally got it to run. Not sure exactly what the problem was in the end.
I checked every earth and every connection. Cleaned and tightened them all.
And removed all the relays and cleaned them too.
It went at last when I was almost ready to give up.
Suspect some corrosion in relays and ignition contacts.
All good now

[Gojeep]

Glad you got it running again.

[zuffen]

Well done.

Nothing better than fixing something where you can't see a logical way for it to function.

I far prefer to sort out why a mechanical thing is having issues than an electrical or worse and electronic devise isn't working.

My Ls3 lost all throttle pedal function (drive by wire) and it turned out to be a faulty oil pressure sensor. It shorted to ground and took out the reference signal to the pedal. Disconnected the oil pressure sensor and the car runs. new sensor ordered to replace the old one.

Buy an OBDII scanner. Even a cheapie will lead you the in the right direction. Mine has paid me back many dozens of times.