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
– Check Throttle Actuator Control (TAC) module connector for water
– Binding or bent throttle plate-failed throttle body

Tech notes

There is a factory service bulletin for the P1516 code on following Cadillac vehicles:

2006-2007 GMC Savana 1500/2500/3500
2006-2007 GMC Sierra
2006-2007 GMC Sierra Flex Fuel
2006-2007 GMC Sierra Hybrid
2006-2007 GMC Sierra Performance Edition
2006-2007 GMC Sierra 2500/3500 HD
2006-2007 GMC Yukon
Factory Service Bulletin GMC OBDII Code P1516

When is the code detected?

The Engine Control Module (ECM) has detected an out of range condition between the predicted and actual throttle position.

Symptoms

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

P1516 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 P1516 code