2.2i Sport M54 OBD code P0121

[motco]

The code translates as: "Throttle Position Sensor/Switch A Circuit Range/Performance Problem" but what does this mean in practical terms on a fully fly-by-wire car? I did have throttle body problems a couple of years ago and my indi garage cleaned it up, cleared the codes and it went well thereafter - until now. Now, the EML, engine, brake, and DSC lights have come on and the reader comes up with P0121. I can clear it but it comes back immediately and the car down on power.

Anybody any experience of this please?

[colb]

Good explanation at this link, car is a Dodge but principle for BMW TPS will be the same shows you how to test it using multimeter and diagnostics. http://www.youtube.com/watch?v=Ww9qVLFHbA8


Colb

[Brian4]

Have a look at this explanation don't know if it will help. http://www.obd-codes.com/p0121

I guess the engine is down on power as it is in 'limp home mode'

The fly by wire has a potentiometer in the throttle pedal which drives a motor on the throttle body.

I assume the DSC is lit as one of it's functions is to reduce the throttle opening in certain situations, not sure why brake light is lit but the engine and EML will be tied to the code above. BMW independent garage or somebody from here with a bmw diagnostic laptop.

[motco]

Colb, that clip looks valuable - I'd like his scanner! I'll study the info tomorrow 'cos I've just got in from dinner with daughter and grandkids at the pub!

Brian4, that sounds about right. I rang Phil at CPC in Amersham (local top rate indie) and he said the brake/DSC comes on because it throws all the traction control sensors out due to conflicting data - like being seasick I assume. He tells me the likely culprit is the TPS in the throttle body but that's integral with it and expensive. Unlikely to be the pedal potentiometer or loom, so get a cheap Ebay throttle body to see if it makes any difference. £20 later and one is on its way. I think that even if it doesn't sort it straight away, I can dis-assemble it and learn about the workings with view to possibly repairing my own. More anon.

Thanks for the help chaps!

[motco]

Well gentlemen (and any ladies who have been bitten by the zedbug) the second hand throttle body did the job!

Thanks again to all those who contributed to the answer - I am now officially a Happy Bunny!