Possible causes

– Poor connection at the Throttle Actuator Control (TAC) module
– Faulty TAC module
– Faulty Throttle Pedal Position (TPP) or Throttle Position (TPS) sensors
– Binding or bent throttle plate-failed throttle body

When is the code detected?

The Powertrain Control Module (PCM) has detected a throttle plate out of position based on commanded and actual throttle plate position

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1515 GMC Description

The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.

The TAC system components include, but are not limited to the following:
– The accelerator pedal position (APP) sensors
– The throttle body
– The powertrain control module (PCM)

Each of these components interface together to ensure accurate calculations and control of the throttle position (TP).

Throttle Body Assembly
The throttle body for the throttle actuator control (TAC) system is similar to a conventional throttle body with several exceptions. One exception being the use of a motor to control the throttle position instead of a mechanical cable. Another exception is the throttle position (TP) sensor. The TP sensor is mounted in the throttle body assembly. The TP sensor is 2 individual TP sensors within the throttle body assembly. Two separate signal, low reference, and 5-volt reference circuits are used to connect the TP sensors and the powertrain control module (PCM). TP sensor 2 signal voltage increases as the throttle opens. TP sensor 1 signal voltage decreases as the throttle opens.

GMC Technical Service Bulletins for P1515 code