Carbon buildup or mechanical binding on the throttle blade or bore; Faulty throttle actuator motor or worn gears inside the throttle body; Throttle position sensor (TPS) signal erratic or out of range; Damaged or corroded wiring between the TAC module and throttle body; Failed TAC module or poor ground connection at the module; Low battery voltage or charging system issue affecting module performance

DTC codes / GM codes / P1516

P1516 · GMThrottle Actuator Control (TAC) Module Throttle Actuator Position Performance

P1516 on GM vehicles indicates that the Throttle Actuator Control (TAC) module has detected a performance error in the throttle actuator position, meaning the actual throttle blade position does not match the commanded position within the expected time and tolerance. The TAC module monitors the throttle actuator motor and position sensors and sets this code when the correlation between commanded and actual position falls outside the calibrated range.

SystemPowertrain

Code typeGM specific

SeverityHigh

Fix difficultyProfessional

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Reduced engine power message displayed on the driver information center
Engine may idle poorly or stall when coming to a stop
Throttle pedal feels unresponsive or sluggish
Transmission may shift harshly or refuse to downshift due to reduced torque management
Often no symptoms besides the warning light and stored code

Common causes, most likely first

Carbon buildup or mechanical binding on the throttle blade or bore
Faulty throttle actuator motor or worn gears inside the throttle body
Throttle position sensor (TPS) signal erratic or out of range
Damaged or corroded wiring between the TAC module and throttle body
Failed TAC module or poor ground connection at the module
Low battery voltage or charging system issue affecting module performance

How to diagnose and fix it

Inspect the throttle body bore and blade for carbon deposits and clean thoroughly with throttle body cleaner
Check battery voltage and charging system output to ensure stable power to the TAC module
Perform a scan tool throttle relearn or TAC module calibration after cleaning or replacement
Backprobe the throttle actuator motor and TPS circuits for voltage drops or intermittent opens
Replace the throttle body assembly if the actuator motor or sensors are faulty
Repair or replace damaged wiring and connectors between the TAC module and throttle body
Replace the TAC module only after all other circuits and components have been verified

Before you replace the throttle body

A dirty throttle body is the most common cause of P1516 on high-mileage GM vehicles, and a proper cleaning often resolves the code without any parts replacement.
The TAC module and throttle body must be calibrated with a scan tool after any service, and skipping the relearn procedure will cause the code to return immediately.
Intermittent wiring faults at the throttle body connector are frequently misdiagnosed as a failed throttle body, so always wiggle-test the harness while monitoring live data.
A weak battery or poor ground can cause the TAC module to set P1516 even when the throttle body is functioning correctly, so verify power and ground integrity first.
This code does not always mean the throttle body is defective; a sticking cruise control cable or pedal position sensor correlation issue can also trigger it on some GM platforms.

Can I keep driving with P1516?

Do not continue driving with P1516 active because the vehicle may enter reduced power mode without warning, limiting speed and acceleration. Have the vehicle diagnosed and repaired before driving at highway speeds or in traffic.

Tools that help

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Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.