P0122 OBD2 Code Guide
P0122 is a sensors diagnostic trouble code. Use this hub to understand the plain meaning, the first checks to run, and which vehicle-specific guides may be more useful before replacing parts.
Throttle/Pedal Position Sensor/Switch A Circuit Low Input
Code P0122 signifies that the Powertrain Control Module (PCM) has detected a voltage signal from the Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) Sensor 'A' circuit that is consistently below its specified minimum operating threshold. This sensor is crucial for informing the PCM about the throttle plate's angle or the accelerator pedal's position, which directly influences fuel delivery and ignition timing. A low input typically indicates an open circuit, a short to ground, a faulty sensor, or an issue with the PCM itself, leading to incorrect throttle control and potential drivability problems.
Code verification standard
P0122 is published with SAE J2012 / ISO 15031-6 code structure plus OBD2 P0122 diagnostic context.
First checks
- - Read all stored and pending codes before clearing anything.
- - Save freeze-frame data so you know speed, load and temperature when the code set.
- - Inspect wiring, connectors, fuses, hoses and obvious leaks tied to the named system.
- - Compare live data against realistic values before buying sensors or modules.
- - Clear the code only after repair and complete a drive cycle to confirm it does not return.
P0122 diagnostic path
- 1Visual Inspection: Begin by thoroughly inspecting the TPS/APP sensor and its associated wiring harness for any visible signs of damage, corrosion, fraying, or loose connections. Pay close attention to the connector pins for bending or contamination.
- 2Voltage Check (Sensor Output): With a multimeter, back-probe the TPS/APP sensor's signal wire while the ignition is on (engine off). Slowly depress and release the accelerator pedal (or manually move the throttle plate if it's a throttle body mounted TPS). The voltage should smoothly transition from a low value (e.g., 0.5V at closed throttle) to a higher value (e.g., 4.5V at wide-open throttle) without any drops, spikes, or dead spots. A consistently low reading confirms the P0122 condition.
- 3Reference Voltage and Ground Check: Verify that the TPS/APP sensor is receiving the correct 5-volt reference signal and a solid ground from the PCM. Use a multimeter to check for 5V at the reference wire and continuity to ground at the ground wire. Absence of either indicates a wiring issue or a PCM problem.
- 4PCM Pin-Out Check: If the sensor and wiring appear good at the sensor end, disconnect the PCM connector and check for continuity between the sensor's signal wire and the corresponding PCM pin. Also, check for any shorts to ground or voltage on the signal wire with the sensor disconnected. This helps isolate whether the issue is in the harness or the PCM.
Verify before repair
- - Replace the faulty Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) Sensor.
- - Repair or replace damaged, corroded, or shorted wiring and connectors in the TPS/APP sensor circuit.
- - Clean corrosion from sensor connectors and ensure a secure connection.
- - In rare cases, replace the Powertrain Control Module (PCM) if internal circuit failure is confirmed after ruling out all other possibilities.
Vehicle-specific pages to check next
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