GMC Terrain & Acadia Code P1516: Meaning, Causes & How to Fix It
Code P1516 means the Throttle Actuator Control (TAC) module commanded the electronic throttle to a specific position, but the throttle position sensors reported back a different value than expected. On crossover models like the Terrain and Acadia, this is frequently tied to throttle body contamination or a specific sensor fault rather than a major mechanical failure.
Jump to a section: What P1516 means · Common symptoms · Try a throttle body cleaning first · When it's the sensor itself · Quick reference table · FAQ
What P1516 Means
Rather than a mechanical throttle cable, your GMC's throttle body is controlled entirely electronically, with the TAC module commanding a position and the throttle position sensors confirming the plate actually moved there. A mismatch between commanded and actual position for long enough triggers P1516 and can restrict engine power as a protective measure.
Common Symptoms
Hesitation, reduced power, rough idle, and in more serious cases, the vehicle entering limp mode with significantly limited acceleration are the most commonly reported symptoms.
Try a Throttle Body Cleaning First
A gummed-up or dirty throttle plate causing physical binding is a common, inexpensive-to-fix cause of this code on crossover models, and a proper throttle body cleaning resolves the issue in many cases without needing any part replacement.
When It's the Sensor Itself
If cleaning doesn't resolve the code, a failing throttle position sensor or wiring issue within the throttle body assembly is the next most likely cause, generally requiring throttle body replacement rather than an individual sensor swap on most of these integrated units.
Quick Reference Table
| Step | What To Try |
|---|---|
| 1 | Clean the throttle body |
| 2 | Inspect throttle body wiring and connector |
| 3 | Clean relevant engine grounds |
| 4 | Replace throttle body assembly if cleaning doesn't resolve it |
Frequently Asked Questions
Is throttle body cleaning something I can do myself?
Yes — with the correct throttle body cleaner and following manufacturer guidance on reconnecting the battery afterward (many systems require a relearn procedure), it's a manageable DIY job for a comfortable owner.
How often should the throttle body be cleaned to prevent this?
There's no strict universal interval, but if you notice early signs like rough idle or hesitation developing gradually, an inspection and cleaning before a code sets is a reasonable preventive step.
Will I need a throttle relearn after cleaning?
Many GM vehicles require an idle relearn procedure after throttle body service, either through a specific drive cycle or a scan tool procedure, to ensure the module recalibrates correctly.
Is it safe to drive with P1516 active?
If the vehicle has entered limp mode, driving is significantly restricted, so it's best to have it diagnosed and repaired promptly rather than continuing with limited throttle response.
Shop the Parts Mentioned
- Wireless Scanner — confirms the code and can monitor throttle position data live.
- Bidirectional Scanner — supports throttle relearn procedures on many models.
- 95-Piece Mechanics Tool Set (Metric & SAE) — for throttle body removal and cleaning.
- 5-Piece Pro Electric Wrench Kit — speeds up throttle body access.
- Taylor Battery Cable Terminal Kits — addresses related ground and connection issues.