The P1516 code on your 2021 GMC Sierra indicates a problem with the intake manifold air control actuator system. This GM-specific code affects your Sierra's throttle body and electronic throttle control system, potentially impacting engine response and power delivery on your 5.3L, 6.2L, or 3.0L diesel engine.
Understanding P1516 on Sierra
The intake manifold air control system manages airflow into the engine through the electronic throttle body. Code P1516 typically relates to a mismatch between commanded and actual throttle position, or issues with the throttle actuator control (TAC) module communication. This is part of GM's drive-by-wire throttle system.
Common Symptoms
- Check engine light illuminated
- Reduced engine power message on dash
- Limited throttle response
- Engine may enter limp mode
- Rough or unstable idle
- Hesitation during acceleration
- Possible stalling
Primary Causes
- Faulty electronic throttle body
- Throttle position sensor malfunction
- TAC module failure
- Wiring issues between throttle body and PCM
- Corroded throttle body connector
- Carbon buildup affecting throttle blade movement
- PCM software requiring update
Diagnostic Procedure for 2021 Sierra
Begin by checking for related codes that may accompany P1516, such as P2135 (TPS correlation) or P2101 (throttle actuator control). Using a GM scan tool, monitor commanded versus actual throttle position. Inspect the throttle body connector for corrosion or damage. Test throttle body motor resistance and TPS sensor voltages. Check for carbon buildup restricting throttle blade movement. Verify wiring integrity between throttle body and PCM.
Repair Solutions
Clean the throttle body carefully using approved throttle body cleaner if carbon buildup is present. Repair corroded connectors and apply dielectric grease. If the throttle body tests faulty, replacement is required - aftermarket throttle bodies are available but OEM is recommended for reliable operation. Update PCM software if a TSB applies. After replacement, the throttle body may require relearn procedure using a scan tool.