OBD-II Code
P1271
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$0–$380
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
$0 (relocating a stacked floor mat or reseating the connector) to $380 (OEM pedal assembly + harness repair).
P1271 is GM's Accelerator Pedal Position Sensor 1-2 Correlation — the drive-by-wire pedal module has two independent position sensors (APP1 and APP2) wired to the ECM as a redundancy check, and the ECM continuously compares them.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP1271 is GM's Accelerator Pedal Position Sensor 1-2 Correlation — the drive-by-wire pedal module has two independent position sensors (APP1 and APP2)…
P1271 is GM's Accelerator Pedal Position Sensor 1-2 Correlation — the drive-by-wire pedal module has two independent position sensors (APP1 and APP2) wired to the ECM as a redundancy check, and the ECM continuously compares them. The two sensors run on opposite slopes by design: APP1 typically sweeps 0.5V at rest to about 2.5V at full pedal, and APP2 sweeps 1.0V at rest to about 5.0V at full pedal (or similar paired ratios depending on year). When the two signals disagree by more than roughly 10% deviation at the same pedal position for a sustained sample period, the ECM sets P1271 and forces a reduced-power mode (limp-home, ~30% throttle authority) for safety.
Cheapest-first ladder
- Scan live data and watch both APP1 and APP2 voltages while slowly pressing the pedal — both should sweep smoothly with no dropouts, flat spots, or spikes. A momentary glitch in one signal is the smoking gun.
- Unplug the pedal connector, inspect for bent pins, green corrosion, or a backed-out terminal, dielectric-grease and reseat.
- Wiggle-test the harness from the pedal connector back to the ECM looking for chafe-through or a broken wire.
- Verify the 5V reference and ground at the pedal connector — both APP sensors usually share a 5V supply and a ground; one bad ground throws BOTH signals off and looks like a correlation fault.
- Replace the pedal assembly ($120-$320 OEM) only after the wiring and grounds check out — most GM pedals are non-serviceable and the sensors are integral to the pedal. Don't replace the pedal before checking the floor mat — a stacked floor mat lifting the pedal off its rest position will throw a correlation code on cold-start KOEO because APP1 and APP2 don't agree on the at-rest baseline.
Vehicle-specific patterns2003-2007 Silverado / Sierra Classic with the 4.8/5.3/6.0 Vortec was the first GM platform to widely adopt drive-by-wire pedals, and the pedal module…
- 2003-2007Silverado / Sierra Classic with the 4.8/5.3/6.0 Vortec was the first GM platform to widely adopt drive-by-wire pedals, and the pedal modules are known to fail at roughly 100k miles with the contact wipers wearing flat — P1271 paired with P2135 (TPS correlation) on these is almost always the pedal assembly itself.
- 2005-2010Cobalt / G5 / HHR with the 2.2/2.4 Ecotec was a heavy P1271 platform — the pedal connector at the firewall bulkhead corrodes from cowl-drain moisture.
- 2008+Equinox / Terrain / Traverse with the 3.6 LLT/LFX has a known pedal-harness chafe point where the wiring bends around the brake-pedal bracket.
- 2007-2010Silverado HD 2500/3500 with the LBZ/LMM Duramax shares the drive-by-wire pedal architecture with the gas trucks and the same wear-out pattern at high mileage; the diesel's reduced-power mode is particularly noticeable because the trucks are often loaded.
Estimated repair$0 (relocating a stacked floor mat or reseating the connector) to $380 (OEM pedal assembly + harness repair).
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