Air intake temperature fault and limited boost errors.

[mike ryan]

I have an allroad 2.5 tdi bau engine. I recently had an ecu light come on. The fault code 17569 G72 p1161 manifold temp sensor open or short to plus. I tried a second hand maf with no joy so ordered a new one as it didn't resolve this fault. The car was still driving but developed an other fault where it would not boost. I have a generic obd code of p0299 turbo under boost. This will sometimes reset it self but other times needs me to stop and turn the ignition off. This occurs when I am under load or trying to overtake on the motor way so isn't ideal. I bought a new maf and stuck that on this morning confident that would resolve it but it's getting worse. I have been using a little obd reader with my phone to reset errors as I go with little results. The last couple of days it has thrown up an egr fault error also. I can't remember what the code was for this.

I have yet to do a detailed investigation as my elsawin wiring diagrams are playing up. Can anyone suggest what to start with before I start pulling things apart. Am I right in saying that the air temperature sensor is built in to the maf.

Can anyone help me to try and diagnose this.


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[amiram]

Check the electrical plug of the G70-G72. ( detached wire or corrosion)

[mike ryan]

An update on my progress. I have found the wiring diagrams online and done continuity checks from the 4 wires that lead back to the ecu and the fifth that is a 12v feed. All of these are good. I notice that the live feed to the sensor is feeding multiple units. Could one of these drag down the live feed. Does the intake temperature sensor use this feed as there are only 2 wires that go Straight back to the ecu. Could the ecu be faulty? I am always skeptical of faults in the ecu unless someone has been messing around and shorted something out. It's normally a wiring or sensor fault but I have checked these.


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[Stavros_Davros]

Mike,

Have you got VCDS?

If you'd like I have a copy on my lappy and could plug in and check in real time what the car is doing?

I'm in Birmingham as well.

[mike ryan]

I have finally managed to solve this. Whilst trying to diagnose this I had the vcds plugged in. I had a code for g72 manifold intake temperature sensor open or short to ground. When I unplugged the maf sensor I got a code for g42 air intake temperature sensor open or short to ground. This was confirmed by the fact that the wiring between the maf and the ecu was fine. Whilst researching I noticed that the pdi uses a map and temp sensor combined. This looks alot like the one fitted to the intercooler. So upon investigation the wiring to this sensor had caught on a pulley from when I did the belts 12 months ago. Once repaired the fault code is gone.

What confused me was that no where is there any mention of a g72 manifold intake temperature sensor in elsawin or anywhere I looked. Also I could see a sensible reading for the intake temperature in vcds. I guess that the ecu measures the temperature post intercooler as well as at the maf.

My copy of elsawin played up hindering my progress. The wiring diagrams stopped displaying. Luckily there's an online one now on a Russian website.

Thanks for the offer of help. Much appreciated.


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[Stavros_Davros]

I have finally managed to solve this. Whilst trying to diagnose this I had the vcds plugged in. I had a code for g72 manifold intake temperature sensor open or short to ground. When I unplugged the maf sensor I got a code for g42 air intake temperature sensor open or short to ground. This was confirmed by the fact that the wiring between the maf and the ecu was fine. Whilst researching I noticed that the pdi uses a map and temp sensor combined. This looks alot like the one fitted to the intercooler. So upon investigation the wiring to this sensor had caught on a pulley from when I did the belts 12 months ago. Once repaired the fault code is gone.

What confused me was that no where is there any mention of a g72 manifold intake temperature sensor in elsawin or anywhere I looked. Also I could see a sensible reading for the intake temperature in vcds. I guess that the ecu measures the temperature post intercooler as well as at the maf.

My copy of elsawin played up hindering my progress. The wiring diagrams stopped displaying. Luckily there's an online one now on a Russian website.

Thanks for the offer of help. Much appreciated.


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You're welcome mate, glad you've sorted it!