P0109: Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent. Meaning, possible symptoms and checks before repair.
Meaning, symptoms, causes and checks
The controller detects interrupted or abnormal MAP/BARO input changes. A static measurement may miss the problem. Recording the signal and supplies under the same conditions is more useful than replacing a sensor from one reading.
Affected system: Powertrain
Symptoms
- Engine warning light; a fallback operating mode is possible.
- Uneven idle, hesitation or reduced power, depending on the control strategy.
Possible causes
- Damaged wiring or connector; unstable reference supply or ground.
- Internal sensor failure; an open or shorted input, depending on the circuit design.
What to check
- Identify the sensor and pin assignment for this code, then read related supply or shared-reference faults.
- Inspect the connector and MAP port; if a sensing hose is fitted, check for cracks, pinching and deposits.
- With the engine off and pressures equalized, compare the reading with actual atmospheric pressure using the OEM tolerance.
- Record signal, reference and ground while gently moving the harness; look for correlated jumps rather than only an average reading.
- After repair, clear codes and recheck MAP/BARO pressure and input under the original recorded conditions, following the manufacturer’s procedure.
Also written as: P0109-00, P010900, PO109 (some scan tools add the fault-type byte, e.g. -00).