Possible causes

– Faulty Throttle Actuator Control (TAC) module
– Throttle Actuator Control (TAC) module harness is open or shorted
– Throttle Actuator Control (TAC) module circuit poor electrical connection
– Throttle plate sticking due to carbon build-up
– Engine Control Module

When is the code detected?

The P2176 code is set whe the difference between the predicted and the actual throttle position is more than a calibrated amount for more than 1.5 seconds.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– No throttle pedal response

P2176 GMC Description

The Engine Control Module (ECM) is the control center for the Throttle Actuator Control (TAC) system. The ECM determines the drivers intent and then calculates the appropriate throttle response. The ECM achieves 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.
Two processors are also used to monitor the TAC system data. Both processors are located within the ECM. Both processors monitor each other’s data to verify that the indicated throttle position is correct.

GMC Technical Service Bulletins for P2176 code