P1156 (Volkswagen): Manifold Absolute Pressure Sensor Circuit Open/Short To Grou… — what it means, the affected system and what to check before replacing parts.
Meaning, symptoms, causes and checks
Manifold Absolute Pressure Sensor Circuit Open/Short To Ground. Source catalogue definition; confirm applicability using vehicle service information.
Affected system: Powertrain
Symptoms
Check Engine light illumination
Rough engine idling
Significant loss of engine power
Increased fuel consumption
Engine hesitation or stalling under acceleration
Possible causes
Damaged or corroded MAP sensor wiring
Defective Manifold Absolute Pressure (MAP) sensor
Short circuit to ground in the sensor signal harness
Disconnected or damaged MAP sensor connector
Faulty Engine Control Module (ECM)
What to check
Inspect the MAP sensor connector for signs of moisture, corrosion, or pushed-out pins
Check the wiring harness between the MAP sensor and the ECM for continuity and shorts to ground using a multimeter
Verify the presence of 5V reference voltage and a good ground at the sensor connector
Monitor the MAP sensor signal voltage via a diagnostic scan tool while the engine is running
Replace the MAP sensor if the circuit tests indicate internal sensor failure