OBD-II Code P1516 — What It Means & How to Fix It

What Does This Error Mean?

P1516 is a GM-specific code indicating that the Throttle Actuator Control (TAC) module has detected that the throttle position does not match the desired position. GM drive-by-wire vehicles use an electronic throttle body — the accelerator pedal sends a signal to the TAC module, which then commands the throttle plate to open. When the actual throttle position and the desired throttle position disagree, P1516 is set. The vehicle may enter reduced engine power mode.

Affected Models

Common in Chevrolet Silverado and GMC Sierra 1500 and 2500 with electronic throttle
Common in Chevrolet Tahoe, Suburban, and Yukon
Common in Chevrolet TrailBlazer and GMC Envoy
Common in Pontiac Grand Prix and Bonneville with TAC system

Common Causes

Failing electronic throttle body with sticky or worn throttle plate mechanism
Carbon buildup on the throttle plate and bore restricting smooth movement
Faulty Throttle Actuator Control module or PCM
Damaged or corroded wiring in the throttle body control circuit
Low battery voltage causing TAC system faults during startup

How to Fix It

Clean the electronic throttle body first. Carbon buildup on the throttle plate and bore is a very common cause of P1516.

Use throttle body cleaner spray and a soft cloth. Do NOT use carburetor cleaner on electronic throttle bodies — it can damage the throttle plate coating.
After cleaning, perform the PCM idle learn procedure. Turn the ignition on without starting for 15 seconds, then start and let idle for 3 minutes.

GM TAC systems require a relearn after cleaning or any throttle body work.
Check battery voltage. Low voltage during startup can cause TAC system faults that trigger P1516.

Charge or replace a weak battery and clear the code before further diagnosis.
Inspect the throttle body wiring harness and connector for corrosion, bent pins, or heat damage.

The throttle body connector on GM trucks is exposed to engine heat and can develop poor connections over time.
If cleaning and electrical checks do not resolve the fault, replace the throttle body assembly.

Always perform the TAC relearn and idle learn procedure after throttle body replacement.

When to Call a Professional

Throttle body cleaning is a good first step and costs very little. Throttle body replacement is $150 to $400 for GM vehicles. TAC module or PCM replacement is $300 to $1,200. After any throttle body replacement, a PCM relearn procedure is required.

Frequently Asked Questions

What does reduced engine power mean on my GM truck?

Reduced engine power is a protective mode where the PCM limits throttle response to prevent engine damage. You will notice sluggish acceleration and limited top speed. The vehicle is still driveable but should not be driven hard. Resolving the underlying fault returns normal power.

Can I clean the throttle body myself to fix P1516?

Yes, and it is often the fix. Remove the air intake tube from the throttle body, spray throttle body cleaner on the plate and bore, and wipe clean. Perform the relearn procedure afterward. Many P1516 codes are resolved with a simple cleaning.

Why does P1516 trigger a reduced power warning?

The TAC system is a safety-critical component. If the actual throttle position does not match what the PCM commanded, it could indicate a stuck-open throttle — a runaway engine risk. GM programmed the system to reduce power and alert the driver when this disagreement occurs.