Manifold Absolute Pressure/Barometric Pressure Circuit High Input
The MAP (Manifold Absolute Pressure) sensor is reporting a pressure reading that is higher than expected, indicating the sensor circuit is receiving excessive voltage or pressure. This causes the engine computer to miscalculate air density and fuel injection timing, leading to poor engine performance and increased emissions.
What You Might Notice
- Check Engine Light (MIL) illuminated
- Engine running rough or poorly
- Decreased fuel economy
- Black or dark smoke from exhaust
- Engine may fail to start or stall frequently
Most Common Causes
- 1
Faulty MAP Sensor
The MAP sensor itself has failed electrically or mechanically, sending a false high-pressure signal to the PCM. This is the most common cause of a P0108 code.
- 2
Vacuum Leak in MAP Supply Line
A crack or disconnection in the vacuum hose between the engine manifold and MAP sensor allows unwanted air into the circuit, causing incorrect pressure readings.
- 3
Wiring Short or Ground Fault
A short circuit on the MAP sensor signal wire or reference voltage wire, or an open ground circuit, prevents proper voltage regulation and causes high-input readings.
- 4
Engine Vacuum Leak
A general engine vacuum leak or worn engine components producing abnormally low manifold vacuum can trigger the high-pressure fault if the sensor interprets the condition incorrectly.
How to Diagnose It
- 1
Check Faulty MAP Sensor — The MAP sensor itself has failed electrically or mechanically, sending a false high-pressure signal to the PCM. This is the most common cause of a P0108 code.
- 2
Check Vacuum Leak in MAP Supply Line — A crack or disconnection in the vacuum hose between the engine manifold and MAP sensor allows unwanted air into the circuit, causing incorrect pressure readings.
- 3
Check Wiring Short or Ground Fault — A short circuit on the MAP sensor signal wire or reference voltage wire, or an open ground circuit, prevents proper voltage regulation and causes high-input readings.
- 4
Check Engine Vacuum Leak — A general engine vacuum leak or worn engine components producing abnormally low manifold vacuum can trigger the high-pressure fault if the sensor interprets the condition incorrectly.
How to Fix It
- 1
Replace MAP Sensor
Remove the faulty MAP sensor from the intake manifold and install a new OEM or quality replacement. Reconnect the vacuum line and electrical connector, then clear the code and test-drive to verify the fix.
- 2
Inspect and Repair Vacuum Lines
Check the vacuum hose running from the engine manifold to the MAP sensor for cracks, splits, or loose connections. Replace any damaged hose or reconnect loose fittings securely.
- 3
Check Wiring and Connectors
Inspect the MAP sensor electrical connector and wiring harness for corrosion, loose pins, or damage. Clean corroded connectors with dielectric grease and reseat them firmly. Check for pinched or damaged wires along the harness.
- 4
Diagnose Engine Vacuum System
Perform a smoke test or visual inspection of the entire engine vacuum system to identify any leaks that may be causing incorrect manifold pressure readings. Repair or replace any failed gaskets, seals, or hoses contributing to vacuum loss.
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