Code Definition

P0109 — Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0109

P0109 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0109 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0109 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0109 code indicates an intermittent fault in the circuit of the Manifold Absolute Pressure (MAP) sensor or the Barometric Pressure sensor. These sensors measure the pressure in the intake manifold and the atmospheric pressure, respectively, and are vital for the Engine Control Module (ECM) to accurately manage fuel injection and ignition timing. An intermittent fault in these circuits can lead to erratic engine behaviour, fluctuating performance, and inefficient fuel consumption.

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