[Biturbos4] Throttle position sensor problem

Richard van der Hoff quattro at rvanderhoff.org.uk
Sun Oct 26 08:01:23 PDT 2008

Hi guys,

I've been having a bit of trouble with my 1999 S4 biturbo, and was 
wondering if anyone had any experience with similar problems.

The symptoms started with an intermittent engine fault light. I plugged 
in the VAG-COM and the problem seemed to be
"17581 - Angle Sensor 2 for Throttle Actuator (G188) Signal too High
             P1173 - 35-10 -  -  - Intermittent".

Now, I've monitored the offending sensor in VAG-COM, and it appears to 
move nicely up and down with the gas pedal. I've also checked for loose 
or corroded connections between the sensor and the ECU, and taken apart 
the sensor and checked for damage inside. All came up blank.

So I put it all back together, thinking "it'll either fix itself, or 
become worse until it's obvious what the problem is".

So yesterday it got worse (on the way to a friend's wedding, of 
course...) - and I lost pretty much all power; basically the engine shut 
itself down to a fast idle. Fortunately after a restart it ran fine again.

I limped it back home today - the problem seems to be getting more 
regular, and have pulled the codes again. I now have, in addition to the 
original fault:

17950 - Angle Sensor 1 for Throttle Actuator (G187): Implausible Signal
             P1542 - 35-10 -  -  - Intermittent
17965 - Charge Pressure Control: Positive Deviation
             P1557 - 35-00 -  -

So presumably both throttle sensors are out of spec at once and the 
engine is shutting itself down to a safe state. I'm hoping P1557 is a 
symptom of the other problems, otherwise it looks like I have a boost 
leak to add to my woes.

In short, does anyone have any experience with throttle-sensor problems, 
any joy in fixing it, and if (as I suspect) I need a new throttle 
sensor, is it possible to obtain one without the entire throttle body?



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