Error Code P1516 is defined as Throttle Actuator Control Module Throttle Actuator Position Performance.

This error code is a manufacturer-specific trouble code, meaning it does not apply to all vehicles makes. Rather, it applies only to specific vehicle makes, such as GM (Chevrolet/GMC), Saturn, etc. Specification of the definition, troubleshooting, and repairs still vary from one make and model to another.


The PCM (powertrain control module, also known as ECM or engine control module) works as the control center of the TAC (Throttle Actuator Control) system. The PCM determines the intention of the driver, and will then calculate the appropriate response on the throttle. The PCM gets the throttle positioning by providing a pulse width modulated voltage to the TAC motor. The TAC system uses the following circuits for Motor control 1 and Motor control 2.

TAC system data is monitored by two processors; both of which are found inside the PCM. Both processors also monitor each data to verify that the indicated throttle position is correct.

Error Code P1516 is detected when the PCM has determined an out of range condition between the predicted and the actual position of the throttle.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Also, since this code affects the throttle actuator position performance, the vehicle will show no throttle response.

Possible Causes

Multiple factors could cause this code, such as:

  • Defective TAC module
  • Open or shorted TAC module harness
  • Poor electrical connection in TAC module circuit
  • Water in TAC module connector
  • Binding or bent throttle-failed body

How to Check

In some cases when this code is present, the PCM will put the vehicle in “fail-safe” mode to prevent the vehicle from being driven much further. And for diagnosis, the technician will examine the system first to accurately diagnose the code and make the appropriate fix, which of course, depends on the specific problem that caused the code.

The technician will check the TAC module for defects; look for open or shorted harness in the TAC module; look for faults in the electrical connection in the TAC module circuit, and look for water in the TAC module connector.

Lastly, the technician will check the throttle body for signs of damage.

How to Fix

Replacement of TAC module

Repair or replace TAC module harness

Fix poor electrical connection in the TAC module circuit

Remove water in TAC module connector

Fix binding or bent throttle-failed body, repair or replace as needed

Make sure you check the ground wire from the TAC harness to the back of the engine block passenger side. In many cases, this could be the culprit of the code.

Also in some cases, the throttle body plate could be sticking because of dirt. You can try cleaning the throttle body before replacing any parts.