What it means
Throttle/Pedal Position Sensor "D" Circuit Low: the signal voltage is below the expected range. Often a short to ground or high resistance in the wiring.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The throttle or pedal position sensor D circuit carries one of the position signals used to judge accelerator or throttle movement. P2122 sets when that signal falls below its expected electrical range, commonly because the signal is shorted to ground, the track is faulty, or resistance at a connector is excessive.
Common causes
Most likely first.
- Pedal sensor track worn
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
How to diagnose it
- Record freeze-frame data and compare live D-channel data with the other position channels to confirm the low reading and note when it occurs.
- Inspect the D circuit connector and harness for rubbed-through insulation, a pinched signal wire, corrosion, or loose terminals that could pull the signal low.
- Check the D signal wire for a short to ground and inspect the sensor ground and reference supply using the wiring diagram and manufacturer's specification.
- Measure circuit continuity and voltage drop through suspect connectors while monitoring the signal, since high contact resistance can mimic a failed sensor.
- If the wiring, ground, and supply are correct, test the sensor's D track and replace the assembly only if it fails the manufacturer's checks.
Common fixes
- Repair a signal wire shorted to ground or damaged by chafing.
- Clean, tighten, or replace corroded high-resistance connector terminals.
- Restore a faulty sensor supply or ground connection.
- Replace the pedal or throttle position sensor assembly if its D track produces a low signal despite a sound circuit.
Can I keep driving?
The low D signal can lead to reduced throttle response or limp mode, so avoid high-speed roads and situations where rapid acceleration is needed. If the vehicle surges or loses response, pull over safely; continued driving can make power delivery unreliable.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.