P0122 medium Severity

P0122: Throttle/Pedal Position Sensor/Switch "A" Circuit Low Input

May cause rough idle, hesitation on acceleration, reduced power, potential stalling and erratic throttle response

Overview

P0122 is a generic OBD‑II trouble code indicating that the Throttle Position Sensor (TPS) “A” circuit is reporting a voltage input lower than the expected range to the engine control unit (ECM/PCM), often due to wiring faults, sensor failure, or improper sensor installation.

Common Symptoms

  • Illuminated Check Engine Light
  • Poor or delayed acceleration
  • Rough, high or low idle
  • Engine stalling or hesitating on throttle
  • Reduced throttle response

Most Common Causes

Faulty throttle position sensor (TPS) high

TPS can degrade or fail electrically causing low signal voltage to ECM/PCM

Damaged or corroded wiring or connectors in TPS circuit high

Open/short circuits or poor connections often cause low voltage readings

Improper sensor installation or misalignment medium

Incorrect loading or rotation of the sensor during installation can give low output

ECM/PCM fault low

Rare but possible; consider after verifying wiring and sensor

Diagnostic Steps

  1. Connect OBD‑II scan tool and confirm P0122 and any related codes
    Expected: P0122 active, observe any other TPS related codes
    Interpretation: Establish confirmed fault and related systems
  2. Visually inspect TPS and associated wiring/connectors for damage, corrosion or loose connections
    Expected: No visible breaks, corrosion, or loose pins
    Interpretation: If faulty wiring found, repair then retest
  3. Using a multimeter, verify reference voltage (~5V) and ground at the TPS connector
    Expected: Stable 5V and good ground
    Interpretation: If no reference or ground, trace wiring and repair
  4. Measure TPS output voltage with throttle moved through range
    Expected: Smooth rising voltage with throttle movement and within spec (> ~0.17–0.20V idle)
    Interpretation: If voltage remains low, sensor likely faulty or misaligned
  5. Check throttle body mechanical operation and pedal position sensor if applicable
    Expected: No binding or obstruction
    Interpretation: Mechanical restriction or pedal sensor errors may mimic low TPS voltage

Repair Solutions

Replace faulty throttle position sensor medium
Estimated Cost: $80 - $300

Typical cost for part and labor varies by vehicle

Repair or replace damaged wiring/connectors medium
Estimated Cost: $50 - $500

Cost varies by extent of wiring damage

Properly install or align TPS medium
Estimated Cost: $10 - $150

Often required after sensor replacement

ECM/PCM inspection or replacement if confirmed faulty hard
Estimated Cost: $300 - $2500

Considered only after all other causes are ruled out

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Replacing TPS without checking wiring and sensor installation alignment
  • Assuming battery voltage or unrelated sensors are cause without proper verification
  • Ignoring potential pedal position sensor issues in drive‑by‑wire systems

Frequently Asked Questions

What does a P0122 diagnostic trouble code signify?

The P0122 code stands for Throttle/Pedal Position Sensor/Switch "A" Circuit Low Input. This generally indicates an issue with the Sensors system.

Should I stop driving if I have P0122?

With a severity level of medium, may cause rough idle, hesitation on acceleration, reduced power, potential stalling and erratic throttle response

Common signs of the P0122 error code

The most typical signs are: Illuminated Check Engine Light, Poor or delayed acceleration, Rough, high or low idle.

Potential causes for OBDII code P0122

The most common causes are: Faulty throttle position sensor (TPS), Damaged or corroded wiring or connectors in TPS circuit, Improper sensor installation or misalignment.

How much does it cost to fix P0122?

It depends on what needs to be fixed. Properly install or align TPS repairs are cheaper (~$150), while ECM/PCM inspection or replacement if confirmed faulty repairs are on the higher end (~$2500).

Is the P0122 code specific to Honda?

This is a universal code. You might see P0122 on Ford, Chevrolet, Toyota, Honda, Nissan, or any other OBD-II vehicle.

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