Possible causes

– Accelerator Pedal Position Sensor 1-2 harness is open or shorted
– Accelerator Pedal Position Sensor 1-2)circuit poor electrcila connection
– Faulty Accelerator Pedal Position Sensor 1-2

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Possible poor acceleration

P1271 GMC Description

The Engine Control Module (ECM) compared the signal from both Accelerator Pedal Position (APP) sensors and detected a voltage difference.

GMC Technical Service Bulletins for P1271 code