Code
P1526
HUMMER
P — Powertrain
Minimum Throttle Position Not Learned
AI status
Completed
Completed
100%
Causes
- Battery disconnected or ECM/PCM reset without completing throttle learn procedure
- New or replaced throttle body / TPS not calibrated
- Throttle position sensor (TPS) or accelerator pedal position (APP) sensor fault
- Wiring harness or connector corrosion, damage, or poor connection
- Contaminated/sticking throttle plate or carbon buildup preventing closed position
- PCM/ECM software or internal fault
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Reduced engine performance or limp-home mode
- Erratic or high/low idle
- Poor throttle response, hesitation or surging
- Vehicle may not start or throttle may be unresponsive until relearned
What to check
- Connect a suitable scan tool and read all stored codes and freeze-frame data.
- Verify battery voltage is stable and within specification (generally >12.4 V) before attempting relearn.
- Inspect throttle body, TPS/APP connectors and wiring for damage, corrosion, or loose pins.
- Using live data, observe TPS/APP sensor voltages/percentages at key ON engine OFF and at closed throttle; compare to expected ranges.
- Check for mechanical throttle binding or carbon build-up by visual inspection of throttle plate movement (engine off, key on) and by commanding throttle plate via scan tool if available.
- Attempt the manufacturer-specified throttle/idle relearn using a factory scan tool or approved procedure.
Signal parameters
- TPS/APP closed-throttle voltage: typically ~0.2–1.0 V (manufacturer-specific)
- TPS/APP wide-open voltage: typically ~4.0–5.0 V
- Sensor reference voltage: ~5 V (check for stable 5 V supply)
- Signal ground continuity: near 0 Ω to chassis ground
- Idle RPM: within specified idle range (commonly 600–1000 RPM depending on engine)
- Throttle position percentage: closed ≈ 0–5%, wide open ≈ 90–100% (varies by vehicle)
Diagnostic algorithm
- Retrieve and record all DTCs, freeze-frame and live data. Note any related codes (TPS, APP, throttle actuator).
- Verify battery and charging system voltage. Charge battery or connect a stable power supply if voltage is low.
- Visually inspect and secure all connectors at the throttle body, TPS/APP sensors, and PCM. Repair any damaged wiring or corroded terminals.
- With scan tool, monitor TPS/APP voltages at key ON engine OFF. Confirm reference voltage (~5 V) and that closed-throttle voltage is within expected range. If voltage out of range, isolate wiring or replace sensor.
- Check throttle plate for smooth movement. Clean throttle body if heavy carbon prevents plate from fully closing.
- Perform the OEM/MANUFACTURER-specific throttle minimum position (idle) learn or throttle body adaptation procedure with a factory or capable aftermarket scan tool. Follow the exact steps in the service manual.
- After successful relearn, clear codes and perform a road test; monitor for recurrence. If relearn cannot be completed or code returns, proceed to component-level testing (resistance/continuity of wiring, replace TPS/throttle body) and consider PCM reflash or replacement only after verifying wiring and components.
- If intermittent faults persist, perform wiggle tests while monitoring live data to locate intermittent wiring faults or connector issues.
Likely causes
- Throttle body not adapted after replacement or battery disconnect
- Faulty throttle position sensor or pedal position sensor
- Intermittent or open/shorted TPS wiring or poor ground
- Throttle plate mechanical restriction (carbon build-up)
- Failed electronic throttle actuator
- PCM needs reflash or replacement
Fault status
Status
Minimum Throttle Position Not Learned — PCM has not stored the closed-throttle calibration. Relearn required; may cause idle or throttle driveability issues until resolved.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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