Faulty accelerator pedal assembly with a worn or failed internal sensor track; Damaged wiring, chafing or corrosion in the APP sensor circuits (signal, reference or ground); Poor connection at the pedal connector, such as spread terminals or water ingress; Shared 5 volt reference or ground fault affecting the sensor supply; Fault in the throttle or engine control module; Pedal obstructed or sticking, for example by a floor mat or debris.

P1271

APP Sensor 1 2 Performance.

GMC
Powertrain
Manufacturer code
High severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
2: AreaFuel and air metering (injector circuit)
71: FaultThe specific fault in that area

What it means

On GMC vehicles P1271 means the Accelerator Pedal Position (APP) sensor 1 and 2 readings do not agree with each other. The pedal assembly contains two sensors that the control module compares constantly, and when the signals fall outside the expected relationship the module sets this code. The module will usually limit engine power as a precaution.

Symptoms

Reduced engine power or limp-home mode
Warning light on, often with a reduced engine power message
Poor or delayed throttle response
Engine stuck at a high or low idle
Hesitation or surging when pressing the accelerator
Cruise control not working

Possible causes

Faulty accelerator pedal assembly with a worn or failed internal sensor tracklikely
Damaged wiring, chafing or corrosion in the APP sensor circuits (signal, reference or ground)likely
Poor connection at the pedal connector, such as spread terminals or water ingresspossible
Shared 5 volt reference or ground fault affecting the sensor supplypossible
Fault in the throttle or engine control modulerare
Pedal obstructed or sticking, for example by a floor mat or debrisrare

How to diagnose

Read all stored codes and freeze frame data, noting whether other throttle, APP or reference voltage codes are present
Check the pedal and footwell for obstructions or a loose floor mat, and confirm the pedal moves smoothly through its full travel
Inspect the pedal connector and wiring for corrosion, damage, water and pushed-back or spread terminals
View live data for APP sensor 1 and 2 while slowly pressing and releasing the pedal, and look for dropouts, jumps or readings that do not track each other
Compare the live readings against the manufacturer's specification, as expected values and relationship vary by model and engine
Measure the 5 volt reference, ground and signal circuits at the pedal connector, and wiggle-test the harness while watching the readings
Check for voltage drop and continuity between the pedal connector and the control module
Check for related technical bulletins or software updates for the specific model and engine before condemning the module

How to fix

Replace the accelerator pedal assembly if the sensor readings are erratic or disagree
Repair or replace damaged wiring and terminals in the APP circuits
Clean and secure the connector, or renew it if corroded or damaged
Repair the shared reference or ground fault if other sensors on the same circuit are affected
Update the control module calibration only if an official update addresses this fault for the vehicle
Replace or reprogram the control module only after the wiring and pedal have been proven good

Can I keep driving?

High severity

Avoid driving unless necessary, as power limiting and unpredictable throttle response can be unsafe in traffic. If it must be moved, do so only a short distance to a safe place or workshop.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.