P0107: MAP Sensor Circuit Low Input

Quick answer

• What the code means: The Powertrain Control Module (PCM) detects a lower than expected voltage signal from the Manifold Absolute Pressure (MAP) sensor.
• Severity: Get it diagnosed soon, but it's generally safe to drive home or to a repair shop. Prolonged driving can lead to poor fuel economy and reduced engine performance.
• Most common cause: A faulty MAP sensor or a vacuum leak.

What the P0107 code means

The P0107 diagnostic trouble code stands for "Manifold Absolute Pressure/Barometric Pressure Sensor Low Input." This means that the vehicle's Powertrain Control Module (PCM) has detected a voltage signal from the MAP sensor that is significantly lower than the expected range for the current engine conditions. Essentially, the MAP sensor, which measures the pressure inside the intake manifold, is sending a signal that indicates very low pressure, which could imply a strong vacuum or a problem with the sensor itself or its circuit.

In simpler terms, your car's computer is seeing a reading from the MAP sensor that suggests there's less air pressure in the engine's intake manifold than there should be. This could be due to a faulty sensor, an electrical issue, or a problem causing an actual vacuum in the intake.

Common symptoms

• Check Engine Light illuminated
• Poor fuel economy
• Rough idle or stalling
• Lack of engine power or hesitation during acceleration
• Difficulty starting the engine
• Black smoke from the exhaust (due to rich fuel mixture)

Common causes

1. Faulty MAP sensor: This is the most frequent culprit. The sensor itself can fail internally, leading to inaccurate voltage readings.
2. Vacuum leaks: Leaks in the intake manifold gaskets, vacuum hoses, or other components can cause an excessively strong vacuum, resulting in a low pressure reading at the MAP sensor.
3. Wiring issues: Damaged, corroded, or open circuits in the MAP sensor wiring harness can lead to an incorrect low voltage signal.
4. Connector problems: A loose or corroded electrical connector at the MAP sensor can disrupt the signal.
5. Faulty PCM: While less common, a defective Powertrain Control Module could misinterpret the MAP sensor signal or have an internal fault. This should only be considered after other possibilities have been ruled out.

How a technician diagnoses it

1. Verify the complaint and perform a visual inspection: The technician will first confirm the P0107 code with an OBD-II scan tool and visually inspect the MAP sensor, its wiring harness, and vacuum lines for any obvious damage, disconnections, or corrosion.
2. Check for Technical Service Bulletins (TSBs): The technician will check for any known issues or recalls related to the vehicle's make and model that might pertain to MAP sensor problems.
3. Monitor live MAP sensor data: Using a scan tool, the technician will observe the live data stream from the MAP sensor. At idle, a healthy MAP sensor typically reads between 1.0V and 1.7V (or 15-22 inHg/50-75 kPa). A voltage consistently below this range would confirm a low input issue. They will also observe how the voltage changes with throttle input; it should increase as the throttle opens.
4. Test MAP sensor voltage and ground: With the ignition on and engine off, the technician will use a multimeter to check for proper 5-volt reference voltage and a good ground at the MAP sensor connector. If either is missing, the wiring or PCM may be at fault.
5. Test MAP sensor signal circuit: The technician will check the signal wire for continuity and for any short to ground or voltage. They