Faulty accelerator pedal position sensor assembly (internal track wear or failure); Signal wire shorted to ground or chafed through in the pedal harness; Open circuit or high resistance in the 5 volt reference supply to sensor 1; Corroded, loose or pushed-out terminals in the pedal sensor connector; Poor ground or sensor return circuit fault; Faulty engine control module or internal reference supply fault.

P1277

Accelerator Pedal Position Sensor 1 Circuit Low Voltage.

Chevrolet
Powertrain
Manufacturer code
Medium severity

How this code is built

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

What it means

P1277 on a Chevrolet means the engine control module has seen the signal voltage from accelerator pedal position sensor 1 fall below the expected range. The module relies on this signal to work out driver demand, so it normally limits throttle response when the fault is present. The cause could be the sensor itself, a short to ground, an open circuit or a supply fault in the pedal circuit.

Symptoms

Engine warning light on, often with a reduced engine power message
Poor or delayed throttle response
Engine stuck at a high or fixed idle, or limited rev range
Car goes into limp-home with restricted power
Hesitation or flat spots when pulling away

Possible causes

Faulty accelerator pedal position sensor assembly (internal track wear or failure)likely
Signal wire shorted to ground or chafed through in the pedal harnesslikely
Open circuit or high resistance in the 5 volt reference supply to sensor 1possible
Corroded, loose or pushed-out terminals in the pedal sensor connectorpossible
Poor ground or sensor return circuit faultpossible
Faulty engine control module or internal reference supply faultrare

How to diagnose

Read all stored and pending codes and note freeze frame data, paying attention to any other pedal, throttle or reference voltage codes.
Visually inspect the pedal sensor connector and harness for damage, water ingress, corrosion and bent or loose terminals.
With the ignition on, view live data for pedal sensor 1 and 2 and sweep the pedal slowly, looking for a low, flat or erratic reading compared with the other sensor.
Wiggle the harness and connector while watching live data to find intermittent faults.
Check the 5 volt reference, signal and ground at the sensor connector against the wiring diagram for your model and engine.
Test the signal and reference circuits for short to ground and continuity back to the control module with the battery disconnected.
Check the sensor return and engine control module grounds for resistance and security.
Only if the wiring and sensor test fine, consider the control module and check for any applicable updates for your model.

How to fix

Replace the accelerator pedal position sensor or pedal assembly if its readings are low, erratic or out of agreement.
Repair or replace any damaged, shorted or open wiring in the signal, reference or ground circuits.
Clean, repair or replace corroded or damaged connector terminals and secure the connector properly.
Restore faulty grounds or sensor return connections.
After the repair, clear the codes, perform any required pedal or throttle relearn for your model, and road test to confirm it does not return.

Can I keep driving?

Medium severity

The car may enter limp-home with reduced power, which can be unsafe in traffic, so avoid driving it more than necessary. Get it diagnosed soon, and stop if throttle response becomes unpredictable.

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