18047 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal
P1639 - 35-10 - - - Intermittent
That's the accelerator pedal sensor. It consists of two potentiometers in one unit on the accelerator pedal assembly. There are two for safety backup so if one fails and is telling the ECU to go full throttle but the other one says part throttle the ECU sill stay part throttle and flag up a fault code like you've got. Before you change the sensor (~£50) you could try a few things.
1/ Clear the fault code and see if it comes back (full version of Vag-Com)
2/ Check the wiring loom to the pedal sensor - may be a loose, corroded or shorted connection.
3/ Use some switch cleaner. Now, I think it's most likely that the potentiometers are of the plastic variety which have a very long service lifetime and are most likely sealed. I've never tried cleaning one of these and don't know how it would respond. The more common or garden carbon track potentiometers (it won't be one of these), like you get on amps, radios, dimmers etc, or the wirewound type, respond very well to switch cleaner (e.g. Servisol) and you can get years more use out of them once cleaned. If it's sealed you may not be able to get the fluid in.
Could be a faulty N75 valve or blocked or leaking hoses. I'd check your hoses first but an N75 is not too expensive. I can't see how your faulty accelerator sensor would have anything to do with this.
hemTT - just replied to your PM but posted here for info to others:
Looks like John-H has covered all the same thoughts I had...
If you have the full version of VAGCOM, check Display group 062, fields 3 and 4 show the two sensors in the pedal...
- Observe display field 3 and 4.
- Slowly depress accelerator pedal completely.
Percent indication in display field 3 must rise uniformly. The tolerance range 12 to 97% is not used completely during this.
Percent indication in display field 4 must also rise uniformly. In the process, the tolerance range of 4 to 49% is not completely utilized.
The indicated value in display field 3 must always be about twice as large as value in display field 4.
Replacement is of the whole accelerator pedal module, very simply unplug cable, undo the two nuts holding it to footwell wall and remove. Install is the reverse of removal. But being the whole module I don't expect it to be cheap unless poss an exchange part... or maybe www.audittspares.co.uk has a secondhand one
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