What does it mean?
P1287 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: APP Sensor 3 Low Voltage .
Symptoms
- MIL (check engine lamp) on, frequently with a reduced-power warning
- Engine returns to idle and will not rev no matter how far the pedal is pressed
- Delayed or dead throttle response, limp mode
- Rough or unstable idle
- Cruise control unavailable
Likely causes
- APP 3 signal wire shorted to ground or open
- Loss of the 5 V reference feeding the pedal sensor
- Corrosion or water inside the pedal connector bridging the signal to ground
- Internally shorted sensor element in the pedal assembly
- Harness chafed where it passes through the bulkhead or along the pedal bracket
- High-resistance sensor ground shifting the signal offset downward
How to fix it
- Check the freeze frame, then read the APP 3 voltage with the key on and the engine off; a value near zero that does not rise during a pedal sweep confirms a low circuit
- Unplug the pedal and measure the 5 V reference and ground at the connector
- Briefly jumper the reference pin to the signal pin at the connector; if the module then reads a high value, the harness and PCM (powertrain control module) side are good
- With both ends disconnected, ohm the signal wire to ground to find a short
- Inspect terminals for green corrosion, moisture and loss of pin tension; repair the harness section if damaged
- Replace the pedal assembly if the sensor itself is shorted internally
- Clear codes, run the pedal relearn if required, and verify full pedal travel in live data