P1516
Throttle Actuator Control (TAC) Module — Throttle Actuator Position Performance
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The P1516 code is a GM-specific code that affects the electronic throttle control system (also called 'drive-by-wire'). It means the PCM has detected that the throttle actuator is not positioning the throttle plate where it's being commanded to go. When this happens, the vehicle typically displays a 'Reduced Engine Power' warning and enters limp mode, severely limiting acceleration.
The most common fix is surprisingly simple: cleaning the throttle body. Carbon deposits accumulate on the throttle plate and bore, creating enough friction that the small electric motor in the TAC module can't move the plate precisely. This causes the position error that triggers the code. A can of throttle body cleaner and 20 minutes can often resolve the issue entirely.
If cleaning doesn't help, the throttle body assembly (which includes the TAC motor and position sensors) may need replacement. On many GM trucks and SUVs, this is a bolt-on part with one connector. After replacement or cleaning, the throttle may need to go through a relearn procedure — typically done by turning the key on for 30 seconds without starting, then starting and letting the engine idle for several minutes. This code should be addressed soon, as limp mode makes the vehicle difficult and potentially unsafe to drive in traffic.
Severity
Symptoms
- •Reduced Engine Power message on the dashboard
- •Vehicle enters limp mode with very limited acceleration
- •Engine hesitates or stalls when pressing the gas pedal
- •Rough or surging idle
- •Throttle feels unresponsive or delayed
Likely Causes
The TAC module that electronically controls the throttle plate has failed or is performing outside of expected parameters, preventing accurate throttle position control.
Carbon buildup inside the throttle body creates mechanical resistance, preventing the throttle plate from reaching the position commanded by the TAC module.
The sensor that reports actual throttle plate position back to the PCM is sending inaccurate readings, creating a mismatch between commanded and actual positions.
Corroded connectors, chafed wires, or loose pins in the TAC module harness create intermittent signal or power delivery problems.
In some cases, a PCM software update is needed to correct false P1516 codes caused by calibration issues in certain GM model years.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Clean the throttle body with throttle body cleaner
- Replace the throttle actuator control module or entire throttle body assembly
- Inspect and repair wiring and connectors to the TAC module
- Replace the throttle position sensor
- Have the PCM reprogrammed with updated calibration if applicable