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Hi All,
I have a m278 in a GL with 210,000 km, It has had all of the m278 problems multiple times over, oil in harness etc. I have cleaned it up multiple times before and got everything back on track for many more kms each time.
This time I had oil at the ECU plugs, all cleaned up and dried out prior to putting back together.
However I now have 3 constant sensor short circuit to positive faults. All appeared after I cleaned the ECU/wiring loom and none before.
P222D12 - Pressure sensor 2 short circuit to positive
P007D12 - Charge are temperature sensor ( bank 1) short circuit to positive
P011800 - Coolant temp sensor 1 short circuit to positive.
Car starts and runs fine, apart from fan on full speed due to temp sensor fault.
I have done some fault finding in the wiring but can find any broken wires etc ( doesnt mean they arent there)
I have also reviewed the wiring diagrams and from what I can figure out all these sensors share a common earth so that could be the issue.
However I am wondering if it is more likely that I have a short in the ECU at this stage?
Or if I do have a wiring fault somewhere causing the short?
I have a carsoft MB4.
Looking for any advice or trouble shooting guides to see if it is wiring or ECU.
Thanks
I would open the ECU to see if has oil in it. I think your car just might be a great candidate for my redneck mod to suck the oil out: Link
I did this over three years ago and it still pulls the oil out and my ECU plug is bone dry. I have a little bottle, maybe 2-3oz, that collects the oil.
Opening the ECU isn't too difficult, but not exactly fun. Remove the screws, obviously, then pry the cover off with a screwdriver. The silicone was pretty strong on mine so I pried, then stuck a razor blade in the cut it, pry repeat. Don't stick the screwdriver or blade in too far because the board isn't too far away inside. See pix, and you can see the thin strip of black silicone all around the edge. And note the pins
I'd keep the ECU level in case there is a lot of oil in. See the copper pins from the plug extending to the board? That's where the oil comes in, so it would drip down into the pan "cover".
If you took the ECU off for that cleaning you mentioned and things went haywire immediately after, I would suspect said oil in now where you don't want it. You can still clean it with Alcohol. I'd use Ethanol or ISO, not Methanol. Or maybe soap n warm/hot water, but I'd rinse well with pure 0ppm water. Bottled water is often 0ppm. Let it dry, maybe with some heat, and see what happens.
Thanks for that advice, I opened up the ECU ( your right not an easy job), but everything inside was dry as a bone and no signs of oil residue.
All back together now, but unfortunately I still have the same faults.
Can anyone tell me the exact locations of the pressure sensor 2, charge air sensor and the coolant temp sensor.
I am having trouble locating a diagram which shows any of the 3 sensors exact locations.
That's good news, because an ECU fail is big $. I'd check that the ECU pins are all straight, which I'm sure you did, but fyi. With all the codes being short to positive I'd still suspect oil still in the ECU plug, but a bad ground may also be the case. You could always make a new ground if you can't find the original.
Hi All,
I have a m278 in a GL with 210,000 km, It has had all of the m278 problems multiple times over, oil in harness etc. I have cleaned it up multiple times before and got everything back on track for many more kms each time.
This time I had oil at the ECU plugs, all cleaned up and dried out prior to putting back together.
However I now have 3 constant sensor short circuit to positive faults. All appeared after I cleaned the ECU/wiring loom and none before.
P222D12 - Pressure sensor 2 short circuit to positive
P007D12 - Charge are temperature sensor ( bank 1) short circuit to positive
P011800 - Coolant temp sensor 1 short circuit to positive.
Car starts and runs fine, apart from fan on full speed due to temp sensor fault.
I have done some fault finding in the wiring but can find any broken wires etc ( doesnt mean they arent there)
I have also reviewed the wiring diagrams and from what I can figure out all these sensors share a common earth so that could be the issue.
However I am wondering if it is more likely that I have a short in the ECU at this stage?
Or if I do have a wiring fault somewhere causing the short?
I have a carsoft MB4.
Looking for any advice or trouble shooting guides to see if it is wiring or ECU.
Thanks
Common ground is gone or high resistance. Check pin 4 on each sensor plug (brown wire). That ground goes to engine block near the back. You probably knocked it loose or it corroded. Not the ECU. Run a temporary ground wire from sensor ground pin to battery negative. If faults clear, you found it.
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