Audi A3 TDI P0121 error

[Dave1957]

Hi all.

New to this forum so thanks for having me.

I own a 2011 Audi A3 2.0 TDI and it had been running like a dream until about a year ago when I noticed that one day when parking at work the car clattered and shuddered when I switched the ignition off. (It was one of those “what the hell” reaction moments).

Since then the car would shudder when switching off after nearly every journey, eventually an engine management light appeared on the dash and I took it to an independent VAG specialist.

He incorrectly replaced the throttle peddle as it had flagged a P0121 TPS code. This cost me £100 for a shiny new peddle that I didn’t need but I digress.

The error reappeared and so I took it to my local garage who removed the throttle body and noted it was full (and I mean full) of carbon. He cleaned it out, put it back on and it ran like a new car for about a month, then the shudder and clatter started again.

5 months later the same engine management light was lit and the throttle was cleaned.

The questions that I have are, has anyone else experienced this? What causes it? What can be done about it?

There is plenty of resource on the net telling people how to clean a throttle body but nothing to say how to prevent the issue in the first place!

Thanks in advance.

[Addy258]

Hi Dave,

I have the exact same issue. What was it and how did you manage to fix it? Also what was the cost involved?

Thank you

[mickeybo]

the po121 code throttle pedal position sensor/switch A circuit range performance certainly points to wiring problem. 0n a throttle pedal has 6 terminals 2x5v feeds 2 earth wires & 2 return wires to the ecu. 60% of defects on vehicles are down to wiring problems not components. The wiring on the throttle pedal would need to be checked out from throttle pedal to ecu corresponding pin nos first by a resistance reading on all 6 wires. Can you post up your engine code