Fault code P0123 – a step-by-step guide to diagnosing and fixing it

Error code P0123 is displayed and the check engine light is on - what does this mean?

DTC P0123 is triggered by the OBD/EOBD system when the throttle signal is outside the expected voltage range. This fault code relates to the throttle position sensor (TPS) and may have slightly different names for different manufacturers, but always refers to an excessively high voltage signal from the sensor.

What causes can this error code have?

• Defective throttle position sensor (TPS)
• Damaged or corroded cable connections to the sensor
• Short circuit in the sensor wiring
• Defective throttle valve or blocked mechanics
• Dirty or sticky throttle body
• Faulty engine control unit (ECU)
• Loose or corroded plug connections
• Voltage problems in the vehicle electrics

What symptoms occur in parallel with fault code P0123?

• Irregular idling: Engine runs unevenly or stalls at idling speed
• Poor throttle response: Delayed response when accelerating
• Jerking when accelerating: Vehicle jerks or stutters during acceleration
• Increased fuel consumption: Significantly higher fuel consumption than usual
• Starting problems: Difficulty starting the engine, especially when the engine is cold
• Emergency running program: Engine runs in safe mode with reduced power

How to fix the problem of error code P0123?

• Repairing the P0123 error code requires a systematic diagnosis of the throttle valve system.
• Replace the throttle body sensor completely and then recalibrate the system
• Remove the throttle body, clean thoroughly and replace if necessary
• Check all cable connections to the TPS, repair or replace damaged cables
• Clean plug connections on the sensor, treat with contact spray and connect firmly
• Check engine control unit for firmware updates and reprogram if necessary
• Measure and repair all electrical wiring between ECU and throttle valve