Code
P1523
HUMMER
P — Powertrain
Throttle Closed Position Performance
AI status
Completed
Completed
100%
Causes
- Faulty throttle position sensor(s) or throttle body position sensor
- Dirty, sticking or mechanically binding throttle plate or throttle body
- Wiring fault: damaged wire, connector corrosion, poor ground, intermittent open/short
- Faulty electronic throttle body (drive-by-wire) or internal motor/gear issue
- PCM/ECM software or calibration error requiring relearn
- Intermittent fault from moisture, contamination, or foreign object in throttle bore
Symptoms
- Check Engine Light (MIL) illuminated; P1523 stored
- Reduced engine power or 'limp' mode
- High or unstable idle, surging, or stalling at idle
- Poor throttle response or hesitation
- Intermittent or permanent inability to return to idle position
What to check
- Retrieve DTCs and freeze-frame data with a scan tool; note related codes and driving conditions
- Visually inspect throttle body, wiring harness and connectors for damage, corrosion or contamination
- Use a scan tool to monitor throttle position sensor (TPS) PIDs and commanded vs actual throttle angle at key on and idle
- Check for stored history and whether code is active/intermittent
- Confirm battery/charging system voltage is within range during tests
Signal parameters
- Closed throttle plate angle: typically near 0°–4° (manufacturer-specific)
- TPS closed/idle voltage: commonly ~0.5–1.0 V (vehicle-specific) for primary sensor
- Redundant throttle position sensors should correlate closely (within manufacturer tolerance)
- Reference voltage: ~5.0 V stable; signal should be smooth without spikes or dropouts
- Idle RPM and load parameters from freeze-frame to reproduce conditions
Diagnostic algorithm
- Read and record all DTCs, freeze-frame and live data. Note if P1523 is active or history. Check for related codes (TPS, pedal sensors, throttle actuator).
- Visually inspect throttle body and intake for carbon buildup, foreign objects or mechanical binding. Check throttle plate movement by hand (engine off) and by commanding with scan tool. Repair/clean if sticking.
- With a diagnostic scan tool, monitor raw and calculated TPS/throttle angle PIDs during key ON (engine off) and at idle. Verify closed angle and voltages. Verify both redundant sensors (if present) correlate and change smoothly.
- Backprobe connector: verify reference voltage (5 V), ground continuity, and TPS signal voltage at closed position. Wiggle harness to check for intermittent faults.
- If sensor voltages out of range or inconsistent, inspect/repair wiring and connectors (pin corrosion, bent pins). Repair open/shorts and re-test.
- If wiring and connectors good but sensor outputs inconsistent or out of spec, replace throttle position sensor or entire electronic throttle body assembly per OEM procedure.
- After repair or replacement, perform throttle body relearn/calibration using scan tool or specified relearn procedure. Clear codes and perform road test to confirm fault does not return.
- If problem persists with good throttle body and sensors, consider PCM reflash or replacement only after exhaustive testing and factory guidance.
Likely causes
- Contaminated or sticking throttle plate preventing return to closed position
- Faulty throttle position sensor(s) or inconsistent sensor correlation (redundant sensors out of tolerance)
- Damaged wiring or poor connector at throttle body or TPS harness
- Throttle body requiring cleaning or replacement
- PCM requires throttle body relearn/calibration after service
Fault status
Status
P1523 — Throttle Closed Position Performance: PCM detects throttle closed position or sensor signal outside expected range; check throttle body, TPS, wiring, and perform relearn.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
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