Throttle/Pedal Position Sensor/Switch "D" Circuit

What it means

The engine computer (ECU) has detected an electrical problem in the accelerator pedal position sensor D (APP D) circuit. The accelerator pedal position sensor D (APP D) tells the ECU how far you are pressing the accelerator pedal on an electronic (drive-by-wire) throttle. The signal is missing or outside the range the ECU will accept.

Symptoms

• Check engine light on
• Reduced engine power or limp mode
• Engine does not respond to the pedal
• Throttle stuck at a fixed idle

Probable causes

Most likely first

1. 1Damaged, corroded or unplugged connector
2. 2Open or shorted signal, reference or ground wire
3. 3Failed sensor
4. 4ECU fault (rare)

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the accelerator pedal position sensor D (APP D) connector and wiring (on the accelerator pedal assembly in the driver footwell). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the accelerator pedal position sensor D (APP D) reading on live data. Both pedal sensors should rise smoothly together as you press the pedal. One usually reads about half the voltage of the other.
4. 4With the key on and the sensor unplugged, check for about 5 volts on the reference wire and a good ground (under 0.1 V drop) on the ground wire. Back-probe the signal wire with the sensor connected and watch the voltage change smoothly.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Repair the damaged wiring or connector
• Replace the accelerator pedal position sensor D (APP D)
• Clear the code and test drive to confirm the repair