01 Understanding & Fixing Catalytic Converter Problems • 02 People Are Shocked To Learn This “Normal” Driving Action Ca… • 03 Decoding Transmission Types: Manual, Automatic, CVT, and DCT • 04 The 1970s Military Aircraft That Still Sees Enemies Before … • 05 The Power of Cruise Control: Advantages, Considerations, an… • 06 How a Failed Deal With Honda Pushed Nissan Into Toyota’s Ar… • 07 Are Modern Cars Too Complicated? A Real-World Review • 08 Power Windows: Common Problems and Solutions • 09 Why Some Faults Only Appear After Leaving the Garage • 10 MAF vs. MAP Sensors: Unraveling the Key Differences •

DTC codes / GM codes / P1515

P1515 · GMControl Module Throttle Actuator Position Performance

P1515 on GM vehicles means the engine control module (ECM) has detected a performance problem with the throttle actuator control (TAC) system, specifically that the actual throttle plate position does not match the commanded position within an expected margin. The ECM monitors the throttle actuator motor and the throttle position sensors, and when the correlation between commanded and actual position falls outside the calibrated range, it sets this code and typically forces the engine into reduced power mode.

SystemPowertrain
Code typeGM specific
SeverityHigh
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Reduced engine power message displayed on the driver information center, often with the engine limited to idle or a low RPM
  • The throttle pedal feels unresponsive or the engine hesitates when accelerating
  • The check engine light and often the traction control or stability control light illuminate
  • The engine may idle poorly or stall immediately after startup
  • Often no symptoms besides the warning light if the fault is intermittent and the ECM has not yet entered limp mode

Common causes, most likely first

  1. Carbon buildup or mechanical binding on the throttle plate or throttle bore, preventing smooth movement
  2. A failing throttle actuator motor inside the throttle body assembly
  3. Worn or damaged wiring or connectors in the throttle actuator control circuit, including chafed harnesses near the throttle body
  4. A faulty throttle position sensor (TPS) or accelerator pedal position sensor (APP) sending inaccurate signals
  5. A weak or failing battery or charging system causing low voltage to the throttle actuator during movement
  6. A corrupted or outdated calibration in the engine control module, sometimes corrected by a software reflash
  7. Internal failure of the engine control module (ECM) itself, though this is the least common cause

How to diagnose and fix it

  1. Inspect the throttle body bore and throttle plate for carbon deposits or debris, and clean them with throttle body cleaner and a soft brush
  2. Check the battery voltage and charging system output, as low voltage can cause the throttle actuator to underperform
  3. Perform a visual inspection of the throttle actuator and throttle position sensor wiring and connectors for corrosion, chafing, or loose pins
  4. Use a scan tool to command the throttle plate through its full range and watch the throttle position sensor readings for smooth, consistent response
  5. Check for technical service bulletins (TSBs) or calibration updates for the ECM that address throttle actuator performance
  6. If the throttle body is mechanically binding or the actuator motor is faulty, replace the throttle body assembly and perform a throttle relearn procedure
  7. If all other components test good, diagnose the ECM and its control circuits before replacing the module

Throttle body cleaning and relearn traps

  • Many technicians replace the throttle body only to find the code returns because the ECM needs a throttle position relearn procedure after any cleaning or replacement, which requires a capable scan tool.
  • Carbon buildup on the throttle plate is a very common cause on high-mileage GM engines, and cleaning the bore often resolves the code without any parts replacement.
  • A weak battery or a voltage drop during cranking can set P1515 intermittently, so always check the battery and connections before condemning the throttle body.
  • The accelerator pedal position sensor and its wiring can cause this code even though the fault appears to be at the throttle body, so inspect both ends of the circuit.
  • This code does not always mean the throttle body is defective; a poor ground connection at the engine block or chassis can cause erratic throttle actuator operation and set P1515.

Can I keep driving with P1515?

If the vehicle has entered reduced power mode, driving is not recommended because the engine may not accelerate beyond idle and could stall in traffic. Even if the light is on without limp mode, avoid highway driving and heavy acceleration until the fault is diagnosed, as the throttle response can become unpredictable.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage