LS3 ECU Wiring Harness

[Jethrow]

Hi everyone,

hoping someone can help with a couple photos.

I am starting to fitt the GMPP ECU and harness to my LS3. However, I have no details as the exactly where the harness should sit on the motor. I think I know where most connectos go, but where to physically run and sucure all the cabling is baffling me.

If anyone has done this recently, and would like to post up some photos, it would be of enormous assistance to me.

Thanks in advance.

[Gav]

Most of the plugs will fit only their intended socket, and your injectors should be numbered, throw it on and start plugging it in, I am sure it will start to make sense.

[400TT]

Due to the length of the main loom your ECU will end up behind the dash either on passenger side or drivers side. See what suits best. I expect you will want to run the loom straight back off the rear of the engine and into the cockpit.

Best result is to tuck the loom section that connects to injectors & coil packs into the recess on each side of the intake manifold under the fuel rails.

Don't be afraid to untape it to re-organise it for fitment.

Connector wise you will be fine, they are all labelled.

Like any wiring loom they can be a little daunting when you first look at them, but a bit of time spent laying them out and they start to fall into place.

[sideshow]

start at the front left coolant temp sensor and cam sensor
and work your way back

if its a left hand drive loom then ecu might go thru firewall on drivers side

the gmmp looms have slightly longer branches to accommodate many motors
so thats y it might look daunting

another thing u can do is plug in the 2 white coils plugs
and start plugging the rest in
if something doesnt fit then flip loom over and swap coil plugs and start again

if u get really stuck goto your locakl holden dealer and take a new l98 comm for a test drive
then take it home and pop the bonnet and compare
then take it back heheheeheh

[byroncobra]

if u get really stuck goto your locakl holden dealer and take a new l98 comm for a test drive
then take it home and pop the bonnet and compare
then take it back heheheeheh

haha, love your work sideshow, a mate of mine was stuck with a flat battery in a Kmart carpark, so he went into the shop bought a battery, fired up his car and left it running while he took it back for a refund......cheaper than calling the NRMA

[sideshow]

hehe
i dont recommend doing it but i just say it for fun
when growing up i was a mechanic at daihatsu and we used to borrow parts from new cars up stairs to try on customers cars
until one day the big boss changed and we were not allowed to touch the cars up stairs
heheheheh

but if u really get stuck u can always post pic of plug or wire colours of plug and ill tell u where it goes but u should be right as its nearly impossible to plug a plug into wrong spot on these lsx motors

[Jethrow]

Thx for the responses everyone.

I have made some progress here but have a couple specific questions I am hoping you may be able to assist with.

First up, ref this connector below, does anyone know what it is for? My harness does not appear to have anything to go into it. FYI, I am using the GMPP stand alone harness.



Also can anyone help with the silver tube outlet also shown.

And then looking at the next image



what is this point for? Is it related to the silver tube?

And I am also stuck on the oil pressure, the connector does not match the unit at the back behind the manifold.

And where does the vehicle speed sensor go? I do see a sensor on the driver side of the TR6060 gearbox, but again, it does not match the hrness connector.

Many thanks, tho I am sure I will have more questions to come.

[sideshow]

First pic is charcoal canister purge valve and pipe is the breather pipe
Gmmp looms won't have purge valve wiring
Breather pipe I think goes to inlet manifold just behind where throttle body runs

Bottom pipe pipe is coolant pipe so water can go out of head and into radiator
Is to bleed air from heads
Needs to be hooked up to top radiator somewhere

Oil pressure don't worry bout
Remove the orig and fit yrngauge or lit sensor

Gmmp looms only have the bare essentials
That's y they are cheap
Some stuff is not perfect

Plus oil pressure sensors change from old to new type that might be why things are different
Yr gbox might not have speed sensor as e later ve boxes didn't have sensor on box
I would need pics to see what it looks like
I would send the loom back and get them to add the bits that's r missing
Heheheh

[sideshow]

Does the loom have a maf plug or any spare plugs in the front of motor
U might be able to use the spare wire to trigger the purge valve
Then repin it at the ecu
Or just remove the valve depending how fussy your engineer
I might have a spare purge valve plug somewhere then you just need to wire it into ecu

[Jethrow]

Thx sideshow.

So for the purge cannister connector, seeing as there is no wiring support, could I just delete the purge valve unit and effectively bypass it with the charcoal cannister? Ie connect the cannistor straight to the back of the thottle body where the valve unit currently goes?

For the vehicle speed sensor, I found another sensor up the back of the gearbox that is the right size, so I guess thats the right one to use. Makes sense it would be near the tailshaft.

And I also forgot to ask, where is the crank sensor? I gather its towards the rear somewhere, but I cannot find it.

Thx again all.

[sideshow]

i would probably run a hose from charcoal cannister to engine but put somehting inside
hose to block it so it looks like it works but it doesnt
i think the valve opens just off idle
maybe hook it up with valve there but just run fake wires to it and tape them to harness
doubt they will know if it works

speed sensor wires will porbably be orange/black wire and a blue/white wire

crank sensor wire is between starter motor and block

get under car and look up the 20mm gap between side of starter and the block
make sure wiring doesnt touch headers when u eventually plug it in
its the hardest plug on the lsx motors to get on and off
it should be on the section of wiring that goes to the drivers side knock sensor

[Jethrow]

Thx for your help here - I have some more thinking to do.

[sideshow]

i think its all up to the enginner and how much they know about these engines
and how much they will pick so as long as it looks like it works u might be right

will they ask about chacoal cannister
maybe run wires to solenoid and tape into loom and they wont do anyhting

another thing is does anyone here know if running no purge valve will affect emissions
it might pressurise tank so u might have to put a 1 or 2mm hole in filler cap

[Zedn]

Running without the purge valve will not effect emissions. The problem will be that un-metered air is coming in the whole time so i suspect would be similar symptoms to an air leak.

Do you know if the valve is normally closed or open without power?

Perhaps a relay can be hooked up using the signal from another sensor that only works when the car is driving.

[sideshow]

if u dont run the electrics to it i would block the hose where it goes to on the motor

[Jethrow]

Any reason we cannot go old school and just use a cannister from an older EFI car that was not ECU controlled, then plumb the 3 lines from the cannister to the fuel tank, the manifold behind the throttle, and to a vent?

At least thats how I think they were plumbed. And don't they only open when the right vacuum combo is reached, usually when not idling. And if you ran the vent from behind the mass flow meter, then the total air should still be accounted for.

[sideshow]

carby style cannisters work the same
the only difference is how they get the vacuum source
the vac line goes to a tiny port on the carby right near the butterfly
and just as butterfly opens it gets vac to that port
if u can replicate that on an lsx manifold with fly by wire then it would work

[Jethrow]

OK, this makes some sense.

So for the three outlets then, we run the vaccuum line to a point just in front of the TB butterfly, the purge line to intake manifold, and the tank line to the tank.

I think thats right ??

[Jethrow]

Originally Posted by sideshow

Oil pressure don't worry bout
Remove the orig and fit yrngauge or lit sensor

Sideshow,

I removed the oil press sensor from the back of the block, but the sensor I have with my gauge will not screw into the same hole. The GM sensor is a larger thread than that found on the gauge sensor.

Can you enlighten me if you can get an adapter to make it fit, or is it better to use the GM sensor and just connect my gauge to it instead via the GM bulkhead connector output. Presumably I just connect to the oil press pin, and to ground.

Any help appreciated.

Thx

[sideshow]

u cant use the holden sensor
pull the sensor off with 27mm deep socket
put it in vice
break off the black plastic part thats glued into the alloy part
centre of alloy part is a tiny hole
drill and tap to suit your oil sensor
if the oil sensor is too big diameter and hits the plastic inlet manifold then fit a 45 degree adapter

just make sure if the new oil sensor is big and heavy that u use good quality 45 degree adapter and that u get good bite into the threads as u dont want sensor breaking of due to vibrations