P2121: Throttle/Pedal Position Sensor/Switch D Circuit Range/Performance
Do not keep driving
Note whether the problem happens at a particular pedal position — light throttle in traffic, say, while hard acceleration is fine. That pattern points at wear inside the sensor rather than at its wiring, and it is a useful thing to report.
What this code means
Sensor D is producing a signal that is electrically valid but implausible — a value outside the travel the pedal physically has, or one that does not change smoothly as the pedal moves.
A reading that jumps or drops out at one particular pedal position is the pattern worth reporting, because it points at a worn track inside the sensor rather than at wiring. Pedals see hundreds of thousands of applications concentrated in the first third of their travel, so that is where the wear appears — and a fault that shows up only in light throttle, in traffic, while full-throttle acceleration is fine, has described exactly that.
Likely causes
Start here
Less common
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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