What are the typical symptoms of P0122?

Reduced power mode or a hard limit on engine speed Idle that will not follow the pedal Throttle position PID stuck at zero percent Sudden power loss over bumps as the harness moves Cruise control disabled with a warning message on the cluster

What causes code P0122?

Signal wire open or shorted to ground between sensor and ECM Five-volt reference lost through a shared sensor feed Sensor ground with high resistance from a corroded terminal Throttle position sensor worn flat at the closed-throttle end Water intrusion in the connector bridging adjacent pins

What recommended checks apply to P0122?

Verify the five-volt reference and ground at the sensor connector Graph signal voltage through a slow pedal sweep for dropouts Jumper reference to signal to see whether the reading rises Inspect for green corrosion and dry the connector fully Repair the harness before replacing the sensor or throttle body

P0122Cars & SUVs

Moderate

P0122Throttle or pedal position sensor A circuit low input

Q: What does code P0122 mean?

P0122 sets when throttle or accelerator pedal position sensor A reports a voltage below the low limit, which the ECM reads as implausible and answers with reduced power or a fixed limp idle. Three wires make this a quick test: confirm the five-volt reference, confirm a clean sensor ground, then watch signal voltage sweep smoothly from roughly 0.5 volts closed to about 4.5 volts wide open with no dropouts. A flat zero volts alongside a healthy reference usually means an open signal wire or a failed sensor, while a reference that also reads zero moves the search upstream to another sensor shorting that shared five-volt feed. Wiggle the harness at the throttle body while watching the graph, and look for water or green corrosion inside the connector before ordering a throttle body.

Content reviewed: August 2026Content reviewed by a heavy-duty technician. About our editorial approach

Check soon

— Reduced-power mode can leave you unable to merge or climb safely, so treat this as a repair before the next long trip rather than a tolerable annoyance.

What does this severity mean?

General guidance only — not a substitute for a professional inspection or official roadside / out-of-service criteria (e.g. CVSA OOSC) in your jurisdiction.

Part of system: Electrical sensing & powertrain inputs · Wire gauge & ampacity tool

Sets when throttle or accelerator pedal position sensor A reports a voltage below the low limit, which the ECM reads as implausible and answers with reduced power or a fixed limp idle. Three wires make this a quick test: confirm the five-volt reference, confirm a clean sensor ground, then watch signal voltage sweep smoothly from roughly 0.5 volts closed to about 4.5 volts wide open with no dropouts. A flat zero volts alongside a healthy reference usually means an open signal wire or a failed sensor, while a reference that also reads zero moves the search upstream to another sensor shorting that shared five-volt feed. Wiggle the harness at the throttle body while watching the graph, and look for water or green corrosion inside the connector before ordering a throttle body.

Parts that may be involved

Throttle or pedal position sensor assembly
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Connector terminals and dielectric grease
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Electronic throttle body if the sensor is not serviceable
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Vehicles often affected

Drive-by-wire vehicles share the five-volt feed among several sensors, so one shorted sensor can pull down multiple signals and set unrelated-looking codes.

Typical symptoms

Reduced power mode or a hard limit on engine speed
Idle that will not follow the pedal
Throttle position PID stuck at zero percent
Sudden power loss over bumps as the harness moves
Cruise control disabled with a warning message on the cluster

Likely causes

Signal wire open or shorted to ground between sensor and ECM
Five-volt reference lost through a shared sensor feed
Sensor ground with high resistance from a corroded terminal
Throttle position sensor worn flat at the closed-throttle end
Water intrusion in the connector bridging adjacent pins

Recommended checks

1
Verify the five-volt reference and ground at the sensor connector
2
Graph signal voltage through a slow pedal sweep for dropouts
3
Jumper reference to signal to see whether the reading rises
4
Inspect for green corrosion and dry the connector fully
5
Repair the harness before replacing the sensor or throttle body

DIY vs professional

DIY: connector inspection and voltage checks with a meter. Pro: harness repair inside the loom and throttle relearn procedures.

Related terms

Content reviewed by a heavy-duty technician. About our editorial approach