Join Date: Feb 2011
Vehicle: 2001 SLK320
Other Toys: 78 MGB, 84 Camaro, 85 Trans Am, 96 Firebird, 00 Sonoma, 06 Escalade
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P0120 Pedal Position Sensor
Haven’t been on the forum much recently, life and a growing family have a way of doing that; but my 2001 SLK320 has been enjoying a pampered life as a weekend cruiser in the summers, and has been trouble free for years now. However, I just took it out of storage for the season today and I am having the first bit of trouble I’ve had in awhile with it….
The car had been in the garage on a battery maintainer all winter, about a couple weeks ago I unplugged the maintainer, but never got around to starting the car. So today I finally got to it, started right up and idled perfectly, so I pulled it outside and let it idle in the driveway for maybe 10 minutes. Got in to take it for a ride and immediately noticed that I had almost no throttle response, I can floor the pedal and the car will only very slowly take off from a stop – bad enough that it’s too dangerous to drive much at all around here.
I shut it off and turned it back on again and this time I got a check engine light, so I ran the code and it came back as “P0120” “Throttle/Pedal Position Sensor A Circuit”. Tried disconnecting the battery, leaving it disconnected for ~10 minutes and reconnected with no change. I’ve also tried the TPS reset procedure (holding pedal to the floor for 5 seconds with the ignition on) without any success.
Curiously, if I have the ignition in the ‘on’ position and clear the P0120 with my code reader, then immediately refresh the code reader the error code comes right back, so I figure whatever it is, is giving the ECU an obviously bad signal all the time. Seems weird that something electronic would die like this while the car is stored, but I guess anything is possible.
Research suggests there are two Throttle Position Sensors? One in the pedal and one somewhere else? Any thoughts on what to do/try next? I would like to avoid just throwing parts at it if possible….But I am also not interested in taking it to a dealer, or even an indy for this quite yet….