P1516 Code: Throttle Actuator Position Performance – Causes & Fixes

What Is Code P1516?

Code P1516 is a General Motors-specific diagnostic trouble code that means the throttle actuator control module has detected a performance problem with the throttle actuator position. In simpler terms, your engine’s computer is commanding the throttle to open or close to a specific position, but the throttle body isn’t responding as expected. This is a high-severity code that affects engine performance and drivability.

What Does P1516 Mean?

The throttle actuator is an electronic component that controls how much air enters your engine. Unlike older vehicles with mechanical throttle cables, modern GM vehicles use a “drive-by-wire” system where the engine control module (ECM) electronically commands the throttle position based on accelerator pedal input and engine operating conditions.

When code P1516 appears, it means:

• The ECM commanded the throttle to move to a specific position
• The throttle actuator didn’t reach that position within the expected time frame
• Or the throttle position feedback sensor is reporting inconsistent data
• The throttle control module detected a mechanical or electrical malfunction

This is different from a simple sensor fault—it indicates an actual performance problem where the throttle mechanism isn’t functioning properly.

Common Symptoms of P1516

• Check Engine Light: Illuminated on the dashboard
• Reduced Engine Power: Engine may go into “limp mode” with limited acceleration
• Hesitation During Acceleration: Sluggish response when pressing the gas pedal
• Stalling: Engine may stall at stops or during driving
• Rough Idle: Engine runs unevenly at a standstill
• Loss of Power Steering: Some vehicles may lose power steering assist
• Difficulty Starting: Engine cranks but takes longer to start
• Erratic Throttle Response: Unpredictable acceleration behavior

Possible Causes (Ranked by Frequency)

1. Faulty Throttle Body Assembly

The throttle body itself may be failing internally. The actuator motor, position sensor, or internal mechanical components can wear out or malfunction, preventing proper throttle control. This is the most common cause of P1516 on GM vehicles.

2. Throttle Control Module Failure

The electronic module that controls the throttle actuator may be defective. This module processes signals from the ECM and sends power to the throttle motor. A failed module will prevent proper throttle response.

3. Wiring or Connector Issues

Corroded, damaged, or loose wiring and connectors between the ECM, throttle control module, and throttle body can interrupt communication and power delivery. Check for water damage, corrosion, or broken pins.

4. Throttle Position Sensor Malfunction

The position feedback sensor inside the throttle body may be sending incorrect signals to the ECM, causing it to think the throttle isn’t responding properly when it actually is.

5. Low Battery Voltage

Insufficient battery voltage can prevent the throttle actuator from operating correctly. A weak battery or charging system problem may trigger this code.

6. Engine Control Module (ECM) Fault

Rarely, the ECM itself may have a software glitch or hardware failure that causes it to misinterpret throttle feedback or send incorrect commands.

7. Carbon Buildup in Throttle Body

Excessive carbon deposits can cause the throttle plate to stick or move sluggishly, preventing it from reaching the commanded position.

Diagnostic Steps

Step 1: Verify the Code and Get a Baseline

Use an OBD-II scanner to confirm code P1516 is present. Note if there are any additional codes stored. Clear the code and take a test drive to see if it returns immediately (indicating an active problem) or if it was a one-time glitch.

Step 2: Perform a Visual Inspection

Inspect the throttle body and related wiring for obvious damage:

• Check for water intrusion or corrosion around the throttle body
• Look for damaged or disconnected connectors
• Inspect wiring for cuts, burns, or pinching
• Verify battery voltage is at least 12.6V when the engine is off

Step 3: Check Battery and Charging System

Measure battery voltage with a multimeter. It should read 12.6V or higher at rest. With the engine running, it should be 13.5-14.5V. A weak battery or failing alternator can cause throttle control issues.

Step 4: Inspect Throttle Body Connectors

Disconnect the throttle body connector and inspect for corrosion, moisture, or loose pins. Clean with electrical contact cleaner if needed. Reconnect firmly and ensure it clicks into place.

Step 5: Test Throttle Response with a Scanner

Using a diagnostic scanner with live data capability, command the throttle to different positions and watch the feedback. The throttle should respond smoothly and reach the commanded position. If it doesn’t, the throttle body or control module is likely faulty.

Step 6: Check for Carbon Buildup

Remove the throttle body and visually inspect for carbon deposits on the throttle plate. If heavily soiled, clean with carburetor cleaner and a soft brush. Excessive buildup can prevent smooth operation.

Step 7: Test the Throttle Control Module

If available, use a scanner to run the throttle control module self-test. This will help determine if the module itself is faulty or if the problem is external (wiring, throttle body, etc.).

Step 8: Replace Components as Needed

Based on diagnostic findings, replace the faulty component. Most commonly, this is the throttle body assembly. If the control module tests bad, it may also need replacement.

Repair Cost Estimates

Throttle Body Replacement: $300–$600 (parts and labor)

• OEM throttle body: $150–$300
• Labor: 1–2 hours at $100–$150/hour

Throttle Control Module Replacement: $200–$400

• Module cost: $100–$200
• Labor: 0.5–1 hour

Wiring or Connector Repair: $100–$300

• If only connectors or wiring need repair, costs are significantly lower

Throttle Body Cleaning: $100–$200

• If carbon buildup is the issue, professional cleaning may resolve the problem

ECM Reprogramming or Replacement: $400–$1,200

• Rarely needed, but if the ECM is faulty, this is expensive

Can I Still Drive With Code P1516?

Severity: HIGH

Code P1516 is considered a high-severity code, and driving with it is not recommended. Here’s why:

• Reduced Power: Your vehicle will likely enter “limp mode,” severely limiting acceleration and highway performance
• Safety Risk: Unpredictable throttle response can make it difficult to accelerate when merging or passing
• Stalling Risk: The engine may stall unexpectedly, especially at intersections
• Loss of Power Steering: Some GM vehicles lose power steering assist when in limp mode
• Transmission Issues: The transmission may shift erratically or refuse to shift properly

Recommendation: Have the vehicle diagnosed and repaired as soon as possible. If you must drive it, do so cautiously and avoid highway speeds. Do not ignore this code.

Frequently Asked Questions