OBD2 Code P0107: Understanding and Fixing a Low MAP Sensor Voltage

The Obd2 Code P0107 signals a problem with your vehicle’s Manifold Absolute Pressure (MAP) sensor circuit, specifically indicating a low voltage reading. This diagnostic trouble code (DTC) is crucial to address promptly as it can affect engine performance and fuel efficiency. As an auto repair expert at obd-de.com, I’ll guide you through understanding, diagnosing, and resolving the P0107 error code.

What is OBD2 Code P0107?

The P0107 code is triggered when your car’s Engine Control Module (ECM) detects that the voltage signal from the MAP sensor is abnormally low for an extended period. The MAP sensor is a vital component in your engine management system. It measures the pressure inside the intake manifold, providing crucial data to the ECM. This pressure reading is influenced by factors like engine speed, throttle position, air temperature, and atmospheric pressure.

The MAP sensor uses a diaphragm that reacts to pressure changes, converting these changes into an electrical resistance. This resistance is then translated into a voltage signal sent to the ECM. A typical MAP sensor has three circuits:

5-Volt Reference Circuit: Supplies a stable 5V to the sensor from the ECM.
Low Reference Circuit (Ground): Provides a ground connection to the sensor from the ECM.
MAP Sensor Signal Circuit: Carries the voltage signal from the sensor back to the ECM, reflecting the manifold pressure.

When the ECM reads a voltage signal consistently below a certain threshold (typically below 0.05 volts for more than 5 seconds), it interprets this as a “low voltage” condition, and sets the P0107 code.

Symptoms of OBD2 Code P0107

A P0107 code can manifest in various symptoms that affect your vehicle’s drivability:

Check Engine Light: The most immediate symptom is the illumination of the Check Engine Light on your dashboard.
Poor Engine Performance: The engine may run rough, hesitate during acceleration, or feel sluggish.
Reduced Fuel Economy: Inaccurate MAP sensor readings can lead to improper air-fuel mixture, decreasing fuel efficiency.
Engine Stalling: In some cases, especially at idle, the engine might stall due to incorrect fuel delivery.
Difficulty Starting: An incorrect MAP sensor signal can make it harder to start the engine.
Failed Emission Test: Due to inefficient combustion, your vehicle may fail an emissions test.

Potential Causes of OBD2 Code P0107

Several factors can lead to a P0107 code. Identifying the root cause is essential for effective repair:

Faulty MAP Sensor: The MAP sensor itself might be defective and providing inaccurate low voltage readings.
Wiring Issues: Damage to the wiring harness or connectors associated with the MAP sensor circuit. This includes:
- Short to Ground: A short circuit in the signal, 5-volt reference, or low reference circuit, causing low voltage.
- Open Circuit: A break in any of the MAP sensor circuits (signal, 5-volt reference, or ground).
- Corrosion or Damage: Corroded or damaged connectors and wiring can disrupt the signal.
Vacuum Leaks: Although less directly related to the electrical circuit, significant vacuum leaks can cause the MAP sensor to read lower pressure than expected, potentially triggering a P0107 in some systems, or contributing to the problem.
ECM Issues: In rare cases, a faulty ECM could be the cause, although this is less common than sensor or wiring problems.
Restricted Intake Manifold or Exhaust System: While less likely to directly cause P0107, restrictions can affect manifold pressure readings.

Diagnosing OBD2 Code P0107: Step-by-Step Guide

Diagnosing P0107 requires a systematic approach. Here are steps a technician would typically follow:

Initial Scan and Verification: Use an OBD2 scanner to confirm the presence of the P0107 code. Clear the code and test drive the vehicle to see if it returns. Note any other DTCs present, as related codes like P0108 (MAP sensor high voltage), P0120-P0123 (Throttle Position Sensor), or P0641/P0651 (Sensor Reference Voltage) can provide additional clues.
Inspect Wiring and Connectors: Visually inspect the MAP sensor and its wiring harness. Look for:
- Damaged, frayed, or melted wires.
- Loose or corroded connectors.
- Signs of rodent damage.
  Repair or replace any damaged wiring or connectors.
Check MAP Sensor Voltage with Scan Tool: With the ignition ON and engine OFF, use a scan tool to read the MAP sensor voltage. It should typically read between 0.05 and 4.9 volts. A reading significantly outside this range, especially consistently low, supports a P0107 diagnosis.
Circuit Testing: If visual inspection doesn’t reveal issues, proceed with circuit testing using a multimeter:
- Ground Circuit Test: Disconnect the MAP sensor connector and, with the ignition OFF for at least 90 seconds, check for continuity (less than 5 ohms resistance) between the low reference circuit terminal and ground. High resistance indicates a problem in the ground circuit.
- 5-Volt Reference Circuit Test: With ignition ON, test for voltage between the 5-volt reference circuit terminal and ground. You should measure between 4.8 and 5.2 volts. Incorrect voltage suggests a problem with the 5V reference circuit or the ECM.
- Signal Circuit Short to Voltage Test: Verify with a scan tool that the MAP parameter is reading low (less than 12 kPa). Higher than expected readings may indicate a short to voltage in the signal circuit.
- Signal Circuit Short to Ground/Open Test: Use a fused jumper wire to connect the signal circuit terminal to the 5-volt reference terminal. The scan tool MAP reading should jump to a high value (greater than 103 kPa). No change or a low reading indicates a short to ground or an open circuit in the signal wire.
MAP Sensor Component Testing: If circuit testing is normal, the MAP sensor itself is suspect. Perform component testing:
- Voltage Variation Test: With the sensor removed but electrically connected (using jumper wires for 5V reference and ground), and a vacuum pump attached, slowly apply vacuum to the sensor. Monitor the voltage output with a multimeter. The voltage should vary smoothly between 0 and 5.2 volts without erratic spikes or drops as vacuum is applied and released. Erratic or out-of-range voltage indicates a faulty MAP sensor.
ECM as Last Resort: If all other tests pass, and you suspect the ECM, this should be the last component considered. ECM issues are less frequent than sensor or wiring problems. ECM testing and replacement might require specialized tools and procedures.

How to Fix OBD2 Code P0107

Based on the diagnosis, common fixes for P0107 include:

MAP Sensor Replacement: If component testing indicates a faulty sensor, replacing the MAP sensor is the most likely solution. Ensure you use a high-quality replacement sensor compatible with your vehicle.
Wiring and Connector Repair: Repair or replace any damaged, corroded, or shorted wiring and connectors in the MAP sensor circuit. Ensure solid, clean connections.
Vacuum Leak Repair: Address any significant vacuum leaks if they are contributing to low MAP readings or engine performance issues.
ECM Replacement (Rare): If the ECM is diagnosed as faulty, it will need replacement and reprogramming, which is best left to a professional technician.

After performing any repairs, clear the P0107 code with an OBD2 scanner and test drive the vehicle to ensure the code does not return and that the symptoms are resolved.

Conclusion

OBD2 code P0107 indicates a low voltage issue within the MAP sensor circuit, which can stem from various causes, most commonly a faulty sensor or wiring problems. A methodical diagnostic approach, as outlined above, is crucial for pinpointing the root cause. While some repairs like sensor replacement and wiring fixes can be DIY for experienced individuals, complex electrical issues or ECM problems are best handled by qualified automotive technicians. Addressing P0107 promptly will restore your vehicle’s performance, fuel efficiency, and ensure it runs smoothly.