Fault code P1142 – a step-by-step guide to diagnosing and fixing it

Error code P1142 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected an error in the fuel supply or mixture ratio. The DTC P1142 is a manufacturer-specific trouble code that mainly occurs in European vehicles and indicates problems with the fuel control or lambda sensor.

What causes can this error code have?

• Defective lambda sensor (oxygen sensor)
• Clogged fuel injectors
• Defective fuel pressure regulator
• Leaks in the intake system
• Dirty mass air flow sensor
• Defective fuel pump
• Clogged fuel filter
• Damaged cables or plug connections
• Defective engine control unit
• Vacuum leaks in the intake tract

What symptoms occur in parallel with fault code P1142?

• Uneven idling: The engine runs unevenly at idle speed
• Loss of power: Noticeable reduction in engine performance
• Increased fuel consumption: Significantly higher fuel consumption than usual
• Starting problems: Difficulty starting the engine
• Jerking when driving: Engine jerks especially under load
• Exhaust odor: Unusual smell from the exhaust
• Check engine light: Permanent illumination of the check engine light

How can the problem with fault code P1142 be rectified?

• Repairing fault code P1142 requires a systematic diagnosis of the fuel system.
• Check the lambda sensor and replace it completely if it is defective, as it is essential for correct mixture control
• Remove the fuel injectors, clean them professionally or replace them with new injectors if they are very dirty
• Test the fuel pressure regulator and replace with a new component if the pressure values are incorrect
• Check the entire intake system for leaks and replace defective hoses or seals
• Remove mass air flow sensor, clean with special cleaner or replace if irreparably damaged
• Check fuel pump for proper function and replace completely if performance drops
• Change the fuel filter as a preventive measure, as a clogged filter impairs the entire fuel supply
• Check all electrical connections to the fuel system and repair or replace damaged cables