Fault code P1198 – a step-by-step guide to diagnosing and fixing it

Error code P1198 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected an error in the engine control unit that is specifically related to the fuel injection or the mass air flow sensor. This manufacturer-specific DTC P1198 mainly occurs in European vehicles and can have different meanings depending on the manufacturer.

What causes can this error code have?

• Defective mass air flow sensor (MAF)
• Dirty or clogged fuel injectors
• Faulty fuel pump or low fuel pressure
• Damaged cable connections to the mass air flow sensor
• Defective engine control unit (ECU)
• Leaks in the intake tract
• Clogged air filter
• Faulty lambda sensor
• Defective throttle valve
• Problems with the exhaust gas recirculation (EGR valve)

What symptoms occur in parallel with error code P1198?

• Loss of power: Noticeable reduction in engine power
• Unsteady idling: Engine runs unevenly at idle speed
• Increased fuel consumption: Significantly higher consumption than usual
• Starting problems: Difficult starting or longer starting times
• Jerking when accelerating: Uneven power delivery
• Black smoke from the exhaust: Indication of incomplete combustion
• Check engine light: Permanent illumination of the warning light

How can the problem with error code P1198 be rectified?

• The repair requires a systematic diagnosis, as this trouble code can have various causes.
• Clean or replace the mass air flow sensor and check the cable connections
• Have the fuel injectors professionally cleaned or replaced
• Check fuel pump and fuel filter and replace if necessary
• Check air filter and replace if dirty
• Check intake tract for leaks and replace damaged hoses
• Clean the throttle valve and test the throttle valve control function
• Check lambda sensors and replace defective sensors
• Clean or replace the EGR valve and flush the lines
• Read out engine control unit and reprogram or replace if necessary