Code P0105: MAP sensor (manifold pressure): circuit fault

Original definition (SAE J2012): Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction^[1][2]

• P0105Manifold absolute pressure or barometric pressure sensor circuit: malfunction.
• P0107Manifold absolute pressure or barometric pressure sensor circuit: low input signal, meaning the sensor voltage is below the expected range.^[6][7][8]
• P0108Manifold absolute pressure or barometric pressure sensor circuit: high input signal, meaning the sensor voltage is above the expected range.^[9][10][11]

1. 1Faulty or damaged MAP (or barometric pressure) sensor, for example through internal wear, heat, vibration or contaminants.^[1][12][13]
2. 2Sensor wiring and connectors in poor condition: damaged wires, loose or corroded connections, open circuit or short circuit.^[1][12][13]
3. 3Leaking or blocked vacuum hose to the sensor, on cars where the sensor is connected to the manifold by a hose.^[1][14]
4. 4Sensor port blocked by dirt or deposits.^[1][3][13]
5. 5Faulty engine ECU, or one that needs reprogramming: Autodoc puts it at the end of its list of checks.^[1]

• Engine warning light (check engine light) on in the instrument cluster.^[4][12][14]Engine warning light: faults that cause it
• Difficulty starting the engine.^[1][12][14]Hard to start: faults that cause it
• Rough or unstable idle, with the engine running unevenly.^{[1][3][12][14]}Vibrations: faults that cause it
• Loss of power, especially when accelerating.^[1][3][14]Less power: faults that cause it
• Jerking or hesitation from the engine while driving.^[1][3]Jerking: faults that cause it
• Increased fuel consumption.^[1][12]Uses more fuel: faults that cause it
• Higher polluting emissions and, in some cases, black smoke from the exhaust.^[1][2]Black smoke: faults that cause it
• In the Saab manual for a 9-3 turbo (Trionic 5), the ECU falls back on basic boost pressure only, that of the turbo itself, and driveability gets worse; in addition, the air conditioning compressor may stop working and the turbo boost gauge shows implausible readings.^[4]Limp mode: faults that cause it

1. 1Read all stored codes: the Saab manual warns that the sensor fault can come with other codes (misfires, closed-loop mixture, boost pressure control) that are worth taking into account.^[4]
2. 2Visually check the sensor connector and wiring (loose or corroded connections, damaged wires) and, if the sensor is connected to the manifold by a vacuum hose, check that the hose is properly attached, with no cracks or blockages.^[1][12][14]
3. 3With a diagnostic tool, watch the sensor value: with the ignition on and the engine off it should read roughly atmospheric pressure (about 102 kPa in the Saab manual) and, with the engine idling, drop clearly (between 40 and 60 kPa on that engine).^[4]
4. 4With a multimeter, check the supply, ground and signal at the connector: a typical analogue sensor is supplied with 5 V and, according to Pico, gives around 4.5 V at atmospheric pressure and 1.5 V at idle. Also measure the continuity of the wiring to the ECU and wiggle the wiring loom while watching the value, to detect intermittent faults.^[1][4][13]
5. 5If the sensor port is dirty, carefully clean it with electrical component cleaner or compressed air and check the reading again.^[1][3][14]
6. 6Only if the wiring, the supply and the hose are fine and the sensor still gives inconsistent values, replace it; the ECU is checked last.^[1][14]