OBD-II Code · Sensors
P2120
Pedal Position Sensor D Circuit
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$80–$400
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Accelerator pedal position sensor D circuit fault — open or shorted.
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 work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
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
- Limp mode
- Forced idle
- Pedal unresponsive
- Check engine light
Likely causes
- Pedal-harness corrosion (GM truck)Most common
- Backed-out pin
- Worn pedal sensor wiper
- Chafed firewall harness
Read the full diagnostic procedureP2120 means the ECM has detected a circuit fault on the 'D' channel of the throttle/pedal position sensor — on most platforms, 'D' is one of the two…
P2120 means the ECM has detected a circuit fault on the 'D' channel of the throttle/pedal position sensor — on most platforms, 'D' is one of the two redundant accelerator pedal position (APP) sensors mounted in the pedal assembly itself. The pedal has two independent potentiometers (APP-D and APP-E) wired through separate ECM pins, and they're calibrated to sweep opposite directions as the pedal moves so the ECM can cross-check them. P2120 specifically means the 'D' channel is open, shorted, or reading a value that's electrically impossible (below ~0.2V or above ~4.8V on most platforms).
Cheapest-first
- unplug the pedal-assembly connector, inspect for backed-out pins, corrosion, or melted plastic, and reseat with dielectric grease.
- Then backprobe APP-D at the pedal connector with the key on — you should see roughly 0.5V at rest and roughly 4.5V at full pedal travel, with a smooth linear sweep in between (a scope is better than a DMM here — a flat-spotted wiper element looks fine on a meter but shows a dropout on a scope).
- If the wire from pedal to ECM is good but the sensor doesn't sweep linearly, the pedal assembly is the fault — and on most platforms the pedal sensor isn't serviceable separately from the pedal arm.
Vehicle-specific patterns2007-2014 GM full-size trucks (Silverado / Sierra / Tahoe / Suburban) with the 5.3L / 6.0L Vortec is the dominant P2120 platform — the APP harness ru…
- 2007-2014GM full-size trucks (Silverado / Sierra / Tahoe / Suburban) with the 5.3L / 6.0L Vortec is the dominant P2120 platform — the APP harness runs under the driver's-side carpet and gets stepped on, water from wet boots wicks into the connector, and the D-channel pin corrodes first because of its position in the connector body. The fix is repinning or replacing the pedal-side pigtail and resealing the connector.
- 2006-2010Dodge Ram 1500 / 2500 throws P2120 from the same harness-corrosion pattern.
- 2008-2013Ford F-150 5.4L 3V sees P2120 from internal pedal-sensor wear where the wiper flat-spots at the rest position from years of foot pressure.
- 2010-2015Chevy Camaro / Cadillac CTS gets P2120 from a chafed harness where it routes through the firewall grommet. Critical: a single bad pedal sensor will throw P2120 alongside a forced-idle code (P2104, P2110, or P2135), so confirm the pedal is the fault before throwing parts — the throttle body itself is innocent.
Look up another code
P2120 — frequently asked
What does a P2120 code mean?
Accelerator pedal position sensor D circuit fault — open or shorted.
What causes a P2120 code?
Common causes: Pedal-harness corrosion (GM truck); Backed-out pin; Worn pedal sensor wiper; Chafed firewall harness.
What are the symptoms of a P2120 code?
Typical symptoms: Limp mode; Forced idle; Pedal unresponsive; Check engine light.
Is it safe to drive with a P2120 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $80-$400.
How do I diagnose a P2120 code?
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. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
More free tools