Code
P1515
GMC
P — Powertrain
Control Module Throttle Actuator Position Performance
AI status
Completed
Completed
100%
Causes
- Throttle body actuator (motor) failing or binding
- Throttle position sensor (TPS) or accelerator pedal position (APP) sensor out of specification or intermittent
- Wiring harness damage, corrosion, poor pin contacts or connector issues
- Low or unstable battery/charging system voltage
- PCM/TCM software fault, calibration mismatch or internal module failure
- Mechanical obstruction or carbon build-up in throttle plate linkage
Symptoms
- Reduced engine power / limp-home mode
- Erratic idle or stalling
- Reduced or delayed throttle response
- Check Engine Light (MIL) illuminated
- Stored DTCs related to throttle/pedal position or actuator control
What to check
- Read and record all stored DTCs and freeze-frame data from the PCM
- Check battery voltage and charging system (should be ~12.4–14.8 V with engine running)
- Visual inspection of throttle body, wiring harness, and connectors for damage or corrosion
- Check for carbon buildup or physical obstruction at throttle plate
- Scan for related codes (TPS/APP/actuator motor) and compare live sensor values
Signal parameters
- TPS/Throttle Blade Position voltage or percent (typical 0.2–4.8 V or 0–100%)
- Accelerator Pedal Position sensor 1 & 2 voltages/percent (dual-channel correlation expected)
- Throttle actuator commanded position vs actual reported position (degrees or percent)
- Actuator motor current draw or duty cycle (where available)
- Battery/ignition feed voltage at throttle body (should be near battery voltage)
- CAN bus/serial data presence between PCM and throttle actuator module
Diagnostic algorithm
- Retrieve all active/pending/recorded codes and freeze-frame data. Note related throttle/pedal codes.
- Check battery state and charging system. Recharge or replace if low/unsteady. Clear codes and retest.
- Perform a visual inspection of throttle body harness and connectors for corrosion, bent pins or water intrusion. Repair as necessary.
- With scan tool, monitor live data: APP1 vs APP2 correlation, commanded throttle position vs actual position, and observe for erratic values while slowly pressing pedal. APP sensors should correlate closely.
- Perform wiggle test on wiring/connectors while monitoring live data for intermittent changes. Backprobe power and ground at the throttle body to verify stable supply.
- Remove and inspect throttle body for carbon buildup or mechanical binding. Clean per factory procedure if contaminated, then recheck operation with scan tool.
- If cleaning and wiring checks do not correct the issue, test throttle actuator motor and position sensor signals (resistance, voltage, current) per service manual procedures.
- If actuator hardware fails electrical tests, replace throttle body assembly. After replacement, perform required relearn/initialization or PCM relearn procedures.
- If throttle body tests good but fault persists, check PCM software level and available technical service bulletins. Reflash/update PCM if recommended.
- If all vehicle-level tests pass and intermittent or anomalous data remain, consider module replacement only after exhaustive verification.
Likely causes
- Contaminated or sticking throttle body (carbon build-up) preventing proper movement
- Intermittent wiring/connector problem at the throttle body or pedal sensor
- Faulty throttle actuator motor or position sensor inside the throttle body
Fault status
Status
The PCM has detected that the throttle actuator/position feedback is not performing within expected parameters. The commanded throttle position and measured position disagree or the actuator cannot reach commanded positions, which may force the vehicle into reduced power mode.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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