What does it mean?
P1246 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Accelerator Position Sensor 1 Circuit Malfunction .
Symptoms
- The MIL or a separate reduced power warning lamp is on
- The engine only idles and does not respond to the pedal
- Severe power limitation, limp mode with a fixed low rev limit
- Sudden loss of drive while the engine keeps running
- Cruise control disabled
- Erratic or surging idle before the fault becomes permanent
Likely causes
- Open circuit, short to ground or short to voltage in the sensor 1 signal wire
- Loss of the 5 volt reference or the sensor ground feeding the pedal module
- Corroded, damp or loose terminals in the pedal connector under the dash
- Worn resistive track inside the pedal position sensor causing dropouts
- Harness damage where the pedal loom passes through the bulkhead or under the carpet
- Water reaching the footwell from a leaking screen seal or heater matrix
- Faulty control module input circuit, verified only after the wiring checks pass
How to fix it
- Compare pedal sensor 1 and 2 percentages on live data while pressing the pedal slowly through its full travel and watch for dropouts
- Unplug the pedal connector and check for damp, corrosion, pushed-back terminals and pin tension
- Measure the 5 volt reference and the sensor ground at the connector with the ignition on
- Back-probe the sensor 1 signal wire and confirm it sweeps smoothly with no spikes to zero or to reference voltage
- Check the signal wire for continuity and for shorts to ground and to voltage with the connector unplugged at both ends
- Wiggle test the pedal harness at the bulkhead grommet while watching live data
- Replace the pedal position sensor assembly when the wiring is proven good, then carry out any required pedal learn procedure