P1125

Code

BUICK P — Powertrain

Accelerator Pedal Position (APP) System

Brand: BUICK

Type: P — Powertrain

Views: UK: 21 EN: 35 RU: 33

AI status

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Page language: EN

Damaged or corroded APP sensor connector or wiring (open, short to ground, short to voltage)
Failed accelerator pedal position sensor or pedal module
Poor or lost 5V reference or sensor ground from PCM
Intermittent wiring fault caused by chafing, pinches, or water intrusion
PCM internal fault or software anomaly
Aftermarket components or recent repairs left connector pins bent or misrouted

Read and record freeze frame and all stored codes; note history and occurrence conditions
Check for Technical Service Bulletins (TSBs) or PCM software updates for this code on the specific Buick model/year
Visually inspect pedal connector and wiring for corrosion, bent pins, breaks, or water damage
Verify related fuses and PCM grounds are secure
Use a scan tool to view live APP sensor values and monitor them while operating the pedal
Backprobe the pedal connector to measure reference voltage, sensor outputs, and ground continuity

Reference voltage (typical): ~5.0 V (key on) supplied to APP sensors
Sensor output typical range: ~0.2–4.8 V across throttle travel (rest near low end, wide open near high end)
Dual-sensor redundancy: two sensor outputs should track each other; one may be inverted depending on design
Expected correlation: sensor signals should change smoothly with pedal travel and remain within a few tenths of a volt of expected curve (manufacturer-specific tolerances)

Connect a capable scan tool, note all codes and freeze frame data; clear codes and attempt to re-create the fault. 2) Perform visual inspection of pedal, connector, and harness for damage, corrosion, or water intrusion. Repair obvious issues. 3) With ignition ON (engine off), backprobe the pedal connector: verify ~5V reference and good ground. If no reference or ground, trace wiring to PCM and check PCM power/grounds/fuses. 4) With scan tool, observe APP sensor voltage/position values at rest and while slowly pressing pedal. Verify smooth, monotonic change and proper end-to-end voltages. 5) Wiggle the harness and connector while monitoring live data to look for intermittent changes. 6) If voltages are out of range or do not change, check continuity of sensor signal wires to PCM; repair wiring as needed. 7) If wiring and reference/ground are good but sensor outputs are incorrect or inconsistent, replace the accelerator pedal module/sensor assembly. 8) After replacement/repair, clear codes, perform relearn procedures if required by manufacturer, and perform road test to confirm code does not return. 9) If fault persists with good wiring and new pedal, consider PCM diagnosis/repair and check for software updates before replacement.

⚠️ Status

MIL ON — APP sensor signals out of range or inconsistent. PCM may enter reduced power (limp) mode.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5 - 2.5 hours

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