Can anyone work this out ? MAP sensor fault code

[clk2000]

Here we are, back again ...

Ok, I have had a chance to have another look at this car. I swapped out the recirculating air flap and the self same issue occurs.

Same error code: P2004-001 High pressure sensor Signal - Short circuit to plus/open circuit (P0108)

Same scenario also .. fault code comes up, erase code, start car - no code. Restart car and code comes back. Rinse and repeat.

All voltages checked and all ok on all circuits. Swapped out both sensors on circuit, no difference.
Swapped out air flap, no difference. ECU change, no difference.

I'm at the end of the line with this one. The only reason I have to get this sorted is if something is wrong with the MAP circuit, then the fueling goes haywire and this won't get an MOT due to emissions. Carsoft 7.4 is supposedly the closest to STAR on these cars and live data even for the Lambda sensors is within range. Should I just ignore this fault and take CO readings instead ?

Any further suggestions ?

 

[Oldspanners]

As you seem to have ruled out the components all that remains is the wiring and connectors.
Is there any corrosion or oil around them as that is a problem with the later M271 engine and causes all sorts of problems or has the previous owner who removed the EML done something more.

 

[clk2000]

Hello Oldspanners and thank you once again for your input.
I thought it best to get Christmas and New year out of the way before I started again with this saga and have had a personal tragedy with losing my Mother to COVID. Things are still up in the air, but re addressing this to take my mind off the situation.
I can confirm that the loom has suffered with the old nemesis of "Oil Wicking". I have just removed the loom from the replacement ECU and it appears there are traces of oil even after cleaning the loom connectors to the ECU. I'm guessing this loom is going to be either toast or I will have to bypass with new wiring. The only loom I have found so far is in Germany but the seller will not ship outside of Germany. I am still looking and if anyone has a loom with the part number of A208 540 2809 they are looking to part with, minus the oil of course, then please let me know.
I'm sure we are on the right track, as thinking about this, when I reset the EML I can run the car as much as 30 mins or more without it reappearing. But, if I restart the car hot, the EML comes back. This is telling me in hindsight that possibly the oil in the loom is warming up and causing it to flow and cause the problem.

 

[mattkh]

Sorry to hear about your mother.
My understanding is that it is the presence of the oil inside the ECU that causes the problem. So, clean that oil. The oil travels up the loom by capillary action. So, you should be able to use the existing loom once you can think of a way to stop the capillary action.

 

[clk2000]

Hello everyone, it's been a while.
Just by way of update, I have now replaced the whole engine harness with a good used unit that had the oil arrestor fitted from about 3 year old (probably as part of recall or service fitment) and is absolutely bone dry of oil and the only thing of note is that my old harness didn't have the earth wire on the same part of the loom as the MAP sensor. It looks like the starter motor had been replaced just before I got the car and my guess is that someone either trapped the wire somewhere, or just plain cut it off.
I have turned the ignition on but not fired up the car yet, cleared the codes and then re scanned just to make sure that everything was ok and it appears that a stored code of exactly the same is showing currently. Did the code actually clear? or is the problem still there is the question.
This car has had replacement ECU (no such code showing before fitment to the car) .. replacement wiring harness (known good in so far as oil contamination) and 2 sets of both MAP sensors.
I am praying that the old code hasn't cleared properly. If it has, I will check voltages of the circuits again and if it doesn't show any faults up with the readings, I'm all out of ideas and options. My next option is to sell the car for scrap and move on with life. It's a shame after all the work, effort and expense put into this car, but I'm fast running out of options here if everything in the circuit including the ECU has been replaced with no cure.

 

[Logicart]

Hello everyone, it's been a while.
Just by way of update, I have now replaced the whole engine harness with a good used unit that had the oil arrestor fitted from about 3 year old (probably as part of recall or service fitment) and is absolutely bone dry of oil and the only thing of note is that my old harness didn't have the earth wire on the same part of the loom as the MAP sensor. It looks like the starter motor had been replaced just before I got the car and my guess is that someone either trapped the wire somewhere, or just plain cut it off.
I have turned the ignition on but not fired up the car yet, cleared the codes and then re scanned just to make sure that everything was ok and it appears that a stored code of exactly the same is showing currently. Did the code actually clear? or is the problem still there is the question.
This car has had replacement ECU (no such code showing before fitment to the car) .. replacement wiring harness (known good in so far as oil contamination) and 2 sets of both MAP sensors.
I am praying that the old code hasn't cleared properly. If it has, I will check voltages of the circuits again and if it doesn't show any faults up with the readings, I'm all out of ideas and options. My next option is to sell the car for scrap and move on with life. It's a shame after all the work, effort and expense put into this car, but I'm fast running out of options here if everything in the circuit including the ECU has been replaced with no cure.

Hi clk2000, I know it is a bit late but did you ever figure your problem out? I am suffering similar problems with my altitude sensor (B18) on my 2005 c180 kompressor with M271 engine. I get the 2013 error code and/or P2228 referring sometimes to short to ground. I have found that I can disconnect the altitude sensor and all readings go back to normal except I get the P2226 code that the altitude sensor circuit is malfunctioning (obvious as it is not connected). However, if I reconnect, the idle chugs and performance drops as well as shooting short term fuel trims up to 25% or more and a P0171 System too lean. Disconnect again and all looks and runs normal. With Bar Altitude sensor connected and MAF disconnected I still get the Lean errors and STFT of 25%. disconnect Bar again and all back to OK. That tells me that the MAF is probably ok.
Like you I now suspect a short in the harness and am tempted to buy a new one. Already have pigtails on and wiring seems oil free.
Therefore, I am just casting a net out to see if you finally found a solution. Cheers.

 

[Logicart]

Hi clk2000, I know it is a bit late but did you ever figure your problem out? I am suffering similar problems with my altitude sensor (B18) on my 2005 c180 kompressor with M271 engine. I get the 2013 error code and/or P2228 referring sometimes to short to ground. I have found that I can disconnect the altitude sensor and all readings go back to normal except I get the P2226 code that the altitude sensor circuit is malfunctioning (obvious as it is not connected). However, if I reconnect, the idle chugs and performance drops as well as shooting short term fuel trims up to 25% or more and a P0171 System too lean. Disconnect again and all looks and runs normal. With Bar Altitude sensor connected and MAF disconnected I still get the Lean errors and STFT of 25%. disconnect Bar again and all back to OK. That tells me that the MAF is probably ok.
Like you I now suspect a short in the harness and am tempted to buy a new one. Already have pigtails on and wiring seems oil free.
Therefore, I am just casting a net out to see if you finally found a solution. Cheers.