What does it mean?
B1303 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Accelerator Pedal Position Signal Error .
Symptoms
- Reduced power or limp mode, the engine may only idle or respond very slowly to the pedal
- Throttle response erratic, the engine surges or hesitates
- Engine and stability system warning lamps lit at the same time
- Cruise control cannot be engaged
- Engine refuses to rev beyond a fixed limit
Likely causes
- Faulty accelerator pedal position sensor, one of its two tracks reading implausibly
- Dirty, corroded or spread terminals at the pedal connector
- Chafed or broken wire in the pedal harness where it passes through the bulkhead
- Loss of the 5V reference or of the sensor ground
- Bus message from the engine controller missing or corrupted, so the receiving module sees no valid pedal value
- Liquid spilled into the driver footwell reaching the pedal connector
- Engine control module input stage failure
How to fix it
- Read both accelerator pedal signals in live data and compare them through the full pedal travel, they should track each other proportionally
- Inspect the pedal connector for corrosion, moisture and spread terminals
- Measure the 5V reference and the sensor ground at the pedal with the ignition on
- Wiggle-test the pedal loom while watching live data for signal dropouts
- Confirm the engine controller is broadcasting a valid pedal value on the bus
- Replace the accelerator pedal assembly if one track is out of range, noisy or drops out
- Repair harness faults, clear codes and verify smooth pedal data across the entire range on a road test