Fault code P0090 – a step-by-step guide to diagnosing and fixing it

Error code P0090 is displayed and the check engine light is on - what does this mean?

The OBD-II system has detected a fault in the control circuit of the fuel metering valve "A", with an open circuit. This DTC affects the fuel injection system and can occur with different manufacturers, although the specific designation of the affected valve may vary.

What can cause this fault code?

• Defective fuel metering valve
• Damaged or interrupted cable to the metering valve
• Corroded or loose plug connections
• Defective engine control unit output stage
• Short circuit in the wiring
• Oxidized contacts on the valve connector
• Defective fuse in the fuel control circuit

What symptoms occur in parallel with fault code P0090?

• Starting problems: The vehicle is difficult to start or starts irregularly
• Erratic idling: The engine runs unstable or rough at idle
• Loss of power: Reduced engine power while driving
• Increased fuel consumption: Significantly increased fuel consumption
• Engine misfires: Jerking or misfiring at various engine speeds
• Exhaust problems: Black or white smoke from the exhaust

How to fix the problem of error code P0090?

• The repair requires a systematic diagnosis of the fuel metering valve circuit.
• Replace the fuel metering valve completely and clean the plug connection, then delete the fault memory and carry out a test drive
• Check the wiring to the metering valve and replace damaged cables, test all connections for continuity
• Clean plug connections on valve and control unit, use contact spray and ensure tight fit
• Have the engine control unit checked for a defective output stage and repair or replace if necessary
• Check fuses in the fuel control circuit and replace blown fuses
• Perform a complete electrical diagnosis with an oscilloscope and measure the signal quality at the metering valve