Hi everyone
Have this Polo in at moment from breakdown job vehicle in limp home with MIL and EPC lights on, Fault code (P1639 Accelerator pedal sensor 1/2 signal improbable) Fault will not clear, actual values show (at closed throttle) sensor 1 16%, sensor 2 41%.
Scope traces for both sensors tested at ecu look good one sensor switching from 0.4v - 1.8v and the other from 0.7v - 3.8v, however i have no tech data to relate these values to? Circuit tests ok volt drop, resistance etc.
I came back to car this morning connected kts and tried to clear fault, which it did, then on checking actual values both pedal sensors reading 16% and increasing within 1 or 2% of each other, Start vehicle and it ran fine for 5 or 10 mins then i noticed sensor 2 had resorted to reading 41% not 16%,fault code returned and lack of response, Rescoped signals at ecu and both looked the same as before with same voltage readings.
I'm suspecting ECU fault but just wondered if anyone else had experienced similar fault with this model.
Cheers
Simon

Hi

Do you have the VW fault code ? your description says pedal, but confusion between accelerator pedal and butterfly position is not un heard of.

could the 41% be a default value if fault code is current ?

Cheers Aidan

Did you scope the ref voltage to the TPPS?

I seem to remember an Ibiza a few years back that I looked at, wouldn't rev and logged codes for TPPS. When scoped the ref voltage was shorting out. I had to disconnect each sensor that used the shared ref until the short went away to find the fault. In my case it was the cam sensor. There was no fault code for the CMP.

Hi guys
thanks for your responses, sorry but i cant shed any further light on this one, customer decided that he didn't want to spend any more money on the car other than the initial diag test and report! So off he went merrily up the road in limp mode
Cheers Simon

I know this car has gone now, but did you consider that the TPS plausibility may have been referring to a plausibility issue with something other than the twin potentiomoeter circuits?

Perhaps the PCM was not liking the engine load feedback for a given throttle opening?

Just a thought.