What does it mean?
P1543 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Throttle Actuation Potentiometer Signal Too Low .
Symptoms
- Check engine light on with reduced power or limp mode active
- Engine will not rev beyond a low limit
- Throttle response dead, delayed or unpredictable
- Unstable idle or stalling when returning to idle
- Cruise control disabled
- Warning may clear after a restart and then return under load
Likely causes
- Signal wire shorted to ground or open between the throttle body and the module
- Missing five volt reference from the module to the sensor
- Worn resistive track inside the throttle position potentiometer
- Water or corrosion in the throttle body connector
- Carbon build-up holding the throttle plate at its lower stop
- Poor sensor ground raising resistance in the measurement circuit
- Failed input circuit in the control module as the final possibility
How to fix it
- Sweep the pedal with the ignition on and watch both throttle position signals in live data
- Measure the five volt reference and the sensor ground at the throttle body connector
- Check the signal wire for a short to ground with the connector unplugged
- Inspect the connector for water, corrosion and bent or spread pins
- Clean the throttle bore and plate, then carry out the throttle relearn procedure
- Replace the throttle body or its potentiometer if the signal is dead or erratic while the wiring is good
- Re-check the commanded and actual throttle values after the repair and clear the reduced power condition