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Discussion Starter #1
Hello everyone,

I have a 2004 C230K coupe (yes, I know this is the sedan forum, but the coupe forum didn't have a W203 section) that is throwing a P0120 code with drama and flair. The car has the ubiquitous 1.8 kompressor engine with a stick shift and has about 120,000 miles on it. The only repair I've ever had to do was a thermostat at 100,000, and a rear differential seal at 110,000. The car has never been in an accident, never modded, etc.

Twice in the past week when I've cold-started the car, it throws the "Check ESP" warning on the dashboard (making me feel like my bank account is about to get much lighter). The engine surges at idle and the car is virtually undriveable.

When I shut off and restart the car, it starts fine ... but this morning it tripped the "Check Engine" light. The code is P0120 - Throttle Position Circuit A, or some verbiage like that.

The simple diagnosis would be to replace the throttle position sensor (I'm assuming it's an expensive black plastic dongle connected to the accelerator pedal?), but I'm wondering if there's anything else I should check first.

Cheers,
-- Mike Helms
 

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Discussion Starter #3
Try this link, you may have some clues to check...
Thanks Dang ... I actually found these two links when I went a'Googling to learn about the P0120 code. I think both of these links discuss vehicles with conventional cable throttle systems, where the TPS is mounted right on the throttle body.

This may sound silly, but I'm going to try tapping the gas pedal a few times before I start the car to see if this might be some sort of mechanical problem with the gas pedal. I'm guessing that after 7 years and 120,000 miles there might be a leaky seal on the TPS that is causing a bit of moisture to enter. Who knows what havoc that is causing in the sensor.

I'll report my findings for our collective wisdom ...

Cheers,
-- Mike
 

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Thanks Dang ... I actually found these two links when I went a'Googling to learn about the P0120 code. I think both of these links discuss vehicles with conventional cable throttle systems, where the TPS is mounted right on the throttle body.

This may sound silly, but I'm going to try tapping the gas pedal a few times before I start the car to see if this might be some sort of mechanical problem with the gas pedal. I'm guessing that after 7 years and 120,000 miles there might be a leaky seal on the TPS that is causing a bit of moisture to enter. Who knows what havoc that is causing in the sensor.

I'll report my findings for our collective wisdom ...

Cheers,
-- Mike
 
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