G60 earth derived on mount goes where?

[Album56 0]

The earth that is derived from the engine mount into the lamda wiring loom on pin 3 goes where? Should it go to the ECU plug, possibly on pin 6. My lamda loom is bad, testing from the lamda plug back into loom there is no heater battery on pin1 with ignition on, pin2 heater earth is ok, pin3 doesnt seem to go to ECU when tested, pin4 the lamda signal goes to pin2 of the ECU plug ok.

I guess that is why my idle has been a bit flakey of late & its running a bit rich, help would be much appreciated.

Mick

[Album56 0]

Found this in an old thread by Supercharged in 2008:-

Plug connects to engine loom at bracket ontop of rear engine mount and on the G60 / 9A probe this bracket also provides an earth which is critical to the engine management, The VR6 part earths thru the loom back to the ECU (I assume) - deffo worth checking all engine mounts are in good condition when fitting a new part as VW give little slack on the cables to allow for movement (altho it's usually the ECU loom side that breaks and you need to either use repair wires or get a new plug from VW - £7ish)

So can I take it that the earth from the bracket should be back thro the loom to the ECU, if so thats busted on mine as well as no 12v heater supply, other wires in the loom, signal & earth from batt -ve at lamda loom plug seem ok.

I guess the break is gonna be where the loom bends out from the bulkhead & continual movement of the engine flexes the wires at that point, I'll strip back some of the outer cover & have a look.

[Album56 0]

Well I dont understand it but the lamda heater battery loom is ok thro to fuse 18 & the fuel pump works ok & yet there is no battery on the red/white wire behind the fuse panel with the ignition on?? Have decided to run ign on battery wire from coil to lamda plug pin1 as its the easiest way .

Still not sure where pin3 (engine mount earth) goes. Anybody any idea.

[Album56 0]

Bump

The earth that is derived from the engine mount into the lamda wiring loom on pin 3 goes where? Should it go to the ECU plug, possibly on pin 6. My lamda loom is bad, testing from the lamda plug back into loom there is no heater battery on pin1 with ignition on, pin2 heater earth is ok, pin3 doesnt seem to go to ECU when tested, pin4 the lamda signal goes to pin2 of the ECU plug ok.

Really need confirmation that the earth from the engine mount into the lambda loom goes back to the ECU so I can rewire it, doesnt seem to go anywhere at the moment but it is "critical to engine management system" , have found a way to easily get +12v ign/on battery to pin1 heater supply so just need this info please anyone.

Mick

[Album56 0]

Registered with CC of Canada to ask question on there, its an active forum & Dennis their technical guy is very knowlegeable, also gonna try looking under the rubber boot on the ECU plug to see if I can recognise the 2w cable with purple & black wires at that end. When you look closely at the loom at the lambda end there are 4 wires, the heater wires are lose inside the sleeving & the other 2 wires, the lambda signal & earth from the mount are in a separate 2w cable inside the sleeving. This makes sense the heater batt/eth comes from fuse board & the other cable goes across to the ECU. I'll update this thread when I get a definitive answer. In my search for an answer it seems that problems with the G60 lambda loom are common as cars get older & symptoms can vary car to car from quite subtle, slightly high idle & rich mixture to almost undriveable.

Mick

[JMC 0]

Not sure why you haven't had an answer to this but to be honest I'm struggling to follow what you are doing (maybe that's the reason). Some pics might help. With regards to earthing, on my lambda sensor connector the earth is directly to some adjacent metal work, it doesn't go anywhere else.

[Album56 0]

Well would you believe it, when I pulled the rubber boot back on the ECU plug the cable from the lambda was easy to recognise with its purple & black wires & the black wire was cut close to the sheath, looks deliberate at manufacture so the earth that we are told is critical for engine management doesnt actually connect to anything. The purple signal wire connects to pin2 as it should.

Seems very odd that VW would go to the trouble of a 4w lambda & terminate the earth at the engine mount end, unless the capacitive effect of the wires is helpful, also I thought I could see the edge of a foil screen where the outer insulation was cut.

The signal wire does carry very small voltage variations, apparently the ECU applies a standing 0.45v & when the probe gets up to temp the signal should vary from 0.2v to 0.8v if its working ok.

 

Still a bit woried about the +50v heater supply, I read somewhere its not fused & the fact that its missing from the red/white wire at the fuse board end suggests its come adrift somewhere there but its impossible to see much behind there.

Anyway one mystery solved ..

Mick

[Album56 0]

Quote from JMC:-

Not sure why you haven't had an answer to this but to be honest I'm struggling to follow what you are doing (maybe that's the reason). Some pics might help. With regards to earthing, on my lambda sensor connector the earth is directly to some adjacent metal work, it doesn't go anywhere else.

 

Thanks for your reply, yes its difficult to follow but all I was trying to do was test the lambda loom (car side), when I found there was no heater supply I assumed wires were broken where the loom is clipped to the bulkhead & bends 90 degrees out to the engine mount but it turns out that part of the loom was fine, the heater supply is missing on a red/white wire connector at the back of fuseboard so looks like thats come adrift behind there somewhere, anyway I have found ignition switched +50v that I can use. Pin 3 on the lambda plug has the black wire that runs with the purple wire in the screened 2w cable all the way back to the ECU where the purple wire terminates pin2 & black wire is cut back it seems at manufacture & doesnt connect to anything. This is the wire that earths on the engine mount at lambda end & we are told is critical to the correct working of engine management? So it connects a good earth at the engine mount to nothing.

Mick

[Album56 0]

Was wondering how I could easily check the oxygen sensor (lambda) was working now I've run a new heater +50v as getting at the wiring with the engine running to check for 0.2 to 0.8v on signal wire isnt easy. Anyway went to fill up with V power 14mile round trip & noticed that its running hotter (leaner mixture?), had been running coolish recently presumably due to over rich mixture because lambda wasnt working. Its quite cool out tonight 10c too so methinks the lambda is having an effect & leaning the mixture as it should do, I have filled the tank & will see how many miles it'll do, used to get around 380miles on a tank of mixed driving .

[G60_Marc 0]

A few things that might help:

 

 

The red/white wire at the sensor plug comes from fuse #18 and is switched via the ecu relay. This relay is controled by the ecu. Fuse #18 also feeds the fuel pump.

 

The red/white wire feeding the sensor should only become live (+12v) when the engine is running, and not when the ignition is just switched on.

 

The brown wire at the sensor plug should be connected to earth (battery negative) via the engine mount. Make sure engine block has a good earth to the battery.

 

The black wire inside the 2 core cable running from the ecu to the sensor is the screen and is wrapped around the purple signal wire as it travels up the cable. It will be connected to earth inside the sensor via the brown earth wire when the sensor is plugged in.

 

The purple wire inside the 2 core cable is the signal from the sensor to the ecu.

 

 

The easiest way to test the output of the sensor would be to tap a wire onto the purple cable of the sensors loom (car side) and run this wire up to your multi-meters positive and put the multi-meter negative lead to earth. Set the meter to the d.c. voltage range that is as close to 1 volt or more, not less. With the sensor plugged in start up the car. With the engine running you should see the voltage on the meter fluctuating between 0 - 1v

 

Also sending an iginition switched +12v to the sensors red/white wire is not a good idea as it will shorten the sensors life.

[Album56 0]

Hi G60_Marc, thanks for the info, that explains a lot so the black wire in the 2w cable acts as a screen to stop any interference with the 0-1v lambda signal & it is earthed thro the engine mount, thats why its critical to the correct working of the engine management without that good earth the signal wire wouldnt be screened properly & induced voltages could upset things. Not happy to hear that +12v heater supply only appears when engine is running, will have a look at it again next week. Basically I've been chasing faults that were'nt there.

Thanks again for the info

Mick