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2004 Land Rover Discovery SE
Helping a friend with his landrover. It’s running rough and rich (black soot in exhaust). Put a scan tool on it and saw the Upstream O2 on Bank 2 was totally dead (0V). Took it out and bench tested it and it’s definitely dead.
As I was looking at the wiring harness I noticed bare wire on the ECM side of the connector. It’s in a really tight area so I had a hard time inspecting it but…it looks like the wire colors are Yel, Gr, Org, and Red. The bare wire showed continuity to ground and the red wire also showed continuity to ground.
I really need a wiring diagram to see what the red wire is and if continuity to ground could have fried the ECM O2 circuit.
Can anyone post/send me a wiring diagram for this vehicle. Thanks!!!
Also any words of wisdom on the ECM condition or rich condition are welcome.
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I don’t know anything about Land Rover wiring, but I do know something about O2 wiring. Your Land Rover probably uses standard Bosch O2 sensors. In that case you’ll see 4 wires coming out of the sensor. 2 whites wires 1 black and 1 gray. The white wires are for the heater and they have no polarity. The black is the positive side of the thermocouple and the gray is the negative. It’s the same for NGK 4-wire sensors as well. Denso sensors are a bit different, then you have 2 blacks 1 blue and 1 white. Blacks are the heater, the blue is positive, white is negative.
Hope that helps.
Thanks for the reply
I’m more interested in the wiring on the ECM side of the connector not the O2 side of the connector.
My logic is that the only way the red should show continuity to ground at all times is if the heater circuit is power side switched. But if not, I think the red wire being grounded would cause some kind of problem.
I wish I had taken a picture, but I didn’t think it would show up well.
Basically about three inches up the connector (on the ECM side) there is what appears to be heat shrink or electrical tape. Out of that there is a small section of bare wire showing and it’s impossible to tell without getting a better look what that bare wire is. All I had time to do was check it and it showed continuity to ground. The red wire in that connector also showed continuity to ground. The bare wire didn’t show continuity to any other wire in the harness. These wires also aren’t covered in wore loom so that also is just asking for problems.
Yup, I believe you are on the right track…
Only one wire should be going to ground.. Which is in the ECM as a Chassis ground and it the ECM adjusts it on and off..
The other two should be functioning “as a battery” sending neg and positive to ECM
The other wire should be getting 12v for the heating element..
-Karl
[quote=”Hanneman” post=109794]I found this for a previous model – it may not apply, but it’s a start. About halfway down the post, there is a wiring diagram in one of the pictures. It looks as there are 2 colors for each wire. Hope it helps.
Thanks man!
I would still really like to get an exact wiring diagram from someone who has Michel. But the one you found is a start. I wonder if that bare wire is a shield, but I’m hesitate to think that. Anyway I’m still really wondering why the red shown continuity to ground.
[quote=”ToyotaKarl” post=109795]Yup, I believe you are on the right track…
Only one wire should be going to ground.. Which is in the ECM as a Chassis ground and it the ECM adjusts it on and off..
The other two should be functioning “as a battery” sending neg and positive to ECM
The other wire should be getting 12v for the heating element..
-Karl[/quote]
Yeah that’s exactly what I was thinking. Is it possible that land rovers are powerside switched like some European cars? Because in that case I could image have a wire that is always a ground because the ECM is just switching on and off power then. My gut is telling me that it’s not power side switched and something is jacked up.
[quote=”JayMann07″ post=109797][quote=”ToyotaKarl” post=109795]Yup, I believe you are on the right track…
Only one wire should be going to ground.. Which is in the ECM as a Chassis ground and it the ECM adjusts it on and off..
The other two should be functioning “as a battery” sending neg and positive to ECM
The other wire should be getting 12v for the heating element..
-Karl[/quote]
Yeah that’s exactly what I was thinking. Is it possible that land rovers are powerside switched like some European cars? Because in that case I could image have a wire that is always a ground because the ECM is just switching on and off power then. My gut is telling me that it’s not power side switched and something is jacked up.[/quote]
What code did you pull off the ECM?
-Karl
Great question! It would be nice to get your take on them. Here’s the report I created
A couple other things…
1) The scan tool showed the MIL had been on for over 2000 miles (the previous owner removed the MIL bulb :angry: ) So some of the codes could have just set some time after the initial problem.
2) In live data mode the B2 S1 O2 read – 0.00V
3) Also in live data STFT B2 – 25 & LTFT B2 – 25 (I’m almost positive it was B2 but I didn’t write it down, but “25” would explain the rich condition. The other bank trim was normal.
I got to brush up on this some more, but off the top of my head…
The P1174 about Lambda…that’s related to O2 (and the code mentions something about maximum). Could that have been the exact moment when the O2 shorted and fried itself and/or the ECM I wonder.
This has a serious engine harness problem with it… Surprise surprise is what you will say…..
Did you trace down why those particular cylinders that were misfiring? Shorted fuel injectors? I find their numbers and positions unusual… Even though there is a P0300….
1 3 5 7
2 4 6 8How did bank 2’s O2 sensor wiring look?
Why are you honing in so much on that dead O2 sensor…(who stripped the wiring?) Have you diagnosed the other issues? I.E. misfire.
I do think you have something very wrong in the wiring…
-Karl
P.S. WHO let A POS LAND ROVER get into the shop? (LOL JK.. know it is a friend)… Maybe explain to him the difference between being able to buy a land rover and OWN a land rover…
[quote=”JayMann07″ post=109809]The P1174 about Lambda…that’s related to O2 (and the code mentions something about maximum).[/quote]
The Lambda sensor is another name for an oxygen sensor. I believe it’s related to the German origin of the sensor.
An O2 sensor fault may be due to a faulty sensor or the sympton of another problem further up the chain.
[quote=”Hanneman” post=109813][quote=”JayMann07″ post=109809]The P1174 about Lambda…that’s related to O2 (and the code mentions something about maximum).[/quote]
The Lambda sensor is another name for an oxygen sensor. I believe it’s related to the German origin of the sensor.
An O2 sensor fault may be due to a faulty sensor or the sympton of another problem further up the chain.[/quote]
[quote=”Hanneman” post=109813][quote=”JayMann07″ post=109809]The P1174 about Lambda…that’s related to O2 (and the code mentions something about maximum).[/quote]
The Lambda sensor is another name for an oxygen sensor. I believe it’s related to the German origin of the sensor.
An O2 sensor fault may be due to a faulty sensor or the sympton of another problem further up the chain.[/quote]
Hanneman,
Here is a thread where I worked with a guy for 2 days solving an o2 heater related circuit problem and succeeding… It would be a nice read for you..
-Karl
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