Fault code P0109 – a step-by-step guide to diagnosing and fixing it

Error code P0109 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system detects a fault in the intake air pressure sensor or barometric pressure sensor (MAP/BARO Sensor Circuit Intermittent). This DTC P0109 indicates an intermittent signal from the sensor that measures the intake manifold pressure or atmospheric pressure. With various manufacturers, this fault code can also be referred to as "Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent".

What can cause this fault code?

• Defective MAP/BARO sensor
• Damaged or corroded plug connections on the sensor
• Interrupted or short-circuited cable connections
• Dirty or blocked vacuum hoses
• Defective engine control unit (ECU)
• Loose sensor bracket or fastening
• Electrical faults in the sensor cable
• Defective intake manifold with leaks

What symptoms occur in parallel with fault code P0109?

• Engine performance: Reduced engine power and poor acceleration
• Idling problems: Unsteady or fluctuating idling
• Fuel consumption: Increased fuel consumption due to incorrect mixture formation
• Starting behavior: Difficulty starting the engine, especially in cold weather
• Exhaust behavior: Black or white smoke from the exhaust
• Check engine light: Permanently illuminated check engine light

How can the problem with error code P0109 be rectified?

• Repairing trouble code P0109 requires a systematic diagnosis of the affected components.
• Replace the MAP/BARO sensor: Replace the defective sensor with an original part or high-quality spare part after checking the function with a multimeter
• Repair cable connections: Check and repair all cable connections to the sensor, including ground connections and signal lines
• Clean plug connections: Clean all plug connections with contact spray and make sure they are tight and corrosion-free
• Replace vacuum hoses: Replace damaged or clogged vacuum hoses and check all connections for leaks
• Engine control unit diagnostics: Have the ECU professionally tested and reprogrammed or replaced if necessary
• Check the intake manifold: Check the intake manifold for cracks or leaks and seal them or replace the component