What does it mean?
P1518 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Throttle Actuator Control Module Serial Data Malfunction .
Symptoms
- Check engine light on with reduced power or limp mode active
- Throttle unresponsive or engine speed capped at a low limit
- Scan tool cannot communicate with the throttle module or drops the connection
- Additional throttle and pedal position codes stored at the same time
- Hesitation or a lurch when pulling away
- Fault may clear after a restart and return later
Likely causes
- Open, shorted or high-resistance conductor in the serial data circuit between the two modules
- Corroded or water-damaged connector at either module
- Poor power supply or ground at the throttle actuator control module
- Damaged harness where it passes the bulkhead or a hot area
- Software or calibration mismatch after a module was replaced or reprogrammed
- Internal failure of the throttle actuator control module
- Aftermarket electrical accessories interfering with the data circuit
How to fix it
- Scan all modules and note network and communication codes, which usually narrow the fault to one branch
- Check the supply voltage and ground quality at the throttle actuator control module
- Measure the serial data circuit for continuity, short to ground and short to voltage between the two module connectors
- Inspect both connectors for water, corrosion and pushed-back terminals
- Check whether the module calibration matches the vehicle after any previous module change or programming
- Disconnect aftermarket accessories to see whether communication becomes stable
- Replace the throttle actuator control module as the last step and carry out the throttle relearn