P1125

Code

GMC P — Powertrain

Accelerator Pedal Position (APP) System

Brand: GMC

Type: P — Powertrain

Views: UK: 24 EN: 47 RU: 39

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or corroded connector at the accelerator pedal assembly
Broken, shorted or chafed wiring between APP sensor and PCM
Failed accelerator pedal position sensor(s) (internal sensor fault)
Poor or missing reference voltage (5 V) or ground to pedal sensor
Contaminated or mechanically binding pedal assembly
Intermittent supply battery/charging system voltage

Symptoms

Check Engine Light (MIL) illuminated
Reduced engine power / limp-home mode
Delayed or no throttle response to pedal input
Unexpected or erratic throttle behavior
Storing of other related throttle/pedal diagnostic codes

What to check

Retrieve freeze frame and full DTC list with a scan tool; note any related throttle codes (e.g., P2135)
Check battery voltage and charging system health before testing
Visually inspect accelerator pedal assembly, connector, and wiring harness for damage, corrosion, or contamination
Backprobe pedal sensor connector and monitor live APP sensor voltages/values while operating pedal
Wiggle test wiring and connector while watching live data for intermittent changes
Confirm 5 V reference and sensor ground at the pedal connector

Signal parameters

Reference supply to APP sensors: nominal 5.0 V (check for stable supply)
Sensor outputs typically vary with pedal travel within approximately 0.5–4.5 V (consult OEM service data for exact ranges)
Both redundant sensors should change smoothly and proportionally as the pedal is moved; one sensor may be offset or inverted depending on design
No abrupt jumps, noise, or dropouts in sensor voltage while moving the pedal
Circuit continuity to ground should be low (good ground), and no short to battery voltage or system ground

Diagnostic algorithm

Connect a scan tool. Record DTCs, freeze frame, and live APP sensor values (Sensor A and Sensor B). Note if any codes are pending or historical.
Verify battery voltage is within specification. Low battery can cause sensor errors during testing.
Visually inspect pedal assembly, connector, and harness for damage, corrosion, loose pins, bent terminals, or signs of water intrusion.
With ignition ON (engine off) backprobe the pedal connector. Verify the PCM 5 V reference is present and stable and that a proper ground is present.
Slowly move the pedal through full travel while observing both sensor voltages/value readings. They should change smoothly and correlate with each other and with pedal position. Note any dead spots, jumps, or out-of-range readings.
Perform a wiggle test on wiring and connector while watching live data to detect intermittent opens/shorts.
If a sensor output is out of range or does not change, isolate that circuit: check continuity to PCM, check for short to power or ground, and repair wiring or connector as needed.
If wiring and connectors test good but sensor readings remain out-of-spec, replace the accelerator pedal assembly per OEM procedure and retest.
After repairs, clear codes and perform road test to confirm the issue is resolved and that codes do not return.
If faults persist after replacing pedal and repairing wiring, consider PCM diagnostic/repair or reflash per manufacturer service information.

Likely causes

Open or short in sensor signal wire
Loose connector pin or water intrusion at pedal connector
One of the redundant APP sensors has failed or is out of tolerance
Reference 5 V supply missing due to fuse/PCM issue
Mechanical wear or foreign object preventing smooth pedal travel

Fault status

⚠️ Status

P1125 — Accelerator Pedal Position (APP) System: PCM detected implausible or out-of-range APP sensor signals or circuit fault. Check pedal sensors, wiring, connectors, 5 V reference and ground.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

Your experience will help others

+100 karma for a short comment :)

Was this AI description helpful?

Your feedback helps improve AI descriptions.

👍 Like 0 👎 Dislike 0

Send to email