P1107 - Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent Low Voltage

Introduction:

The P1107 diagnostic trouble code (DTC) indicates an issue with the Manifold Absolute Pressure (MAP) sensor circuit. Specifically, the engine control unit (ECU) has detected an intermittent low voltage signal from the MAP sensor. This sensor is crucial for engine performance, as it provides the ECU with information about the pressure inside the intake manifold, allowing it to accurately adjust fuel delivery and ignition timing. Ignoring this code can lead to poor fuel economy, rough idling, and potentially damage to the engine.

Comprehensive Information Table:

Detailed Explanations:

1. Key Components:

• Manifold Absolute Pressure (MAP) Sensor: This sensor measures the pressure inside the intake manifold. It's typically a three-wire sensor: one wire for voltage supply (usually 5V), one for ground, and one for the signal voltage that varies with pressure. The signal voltage is sent to the ECU.
• Engine Control Unit (ECU): The ECU is the brain of the engine management system. It receives data from various sensors, including the MAP sensor, and uses this information to control fuel injection, ignition timing, and other engine parameters.
• Wiring Harness and Connectors: The wiring harness provides the electrical connections between the MAP sensor, the ECU, and the power source. Connectors ensure a secure and reliable connection between the components.

2. Description:

The P1107 code specifically indicates that the ECU has detected an intermittent low voltage signal from the MAP sensor. This means the voltage signal is occasionally dropping below the expected range. The ECU uses the MAP sensor signal to determine the engine's load. A low voltage signal from the MAP sensor may be interpreted by the ECU as a very low engine load or even a vacuum leak, leading to incorrect fuel and ignition adjustments. An "intermittent" fault means the problem doesn't occur constantly, making diagnosis more challenging.

3. Possible Causes:

• Faulty MAP Sensor: The sensor itself may be failing and providing an inaccurate or intermittent signal. This is a common cause. Internal corrosion or damage can cause the sensor to malfunction.
• Wiring Issues: Damaged, corroded, or loose wiring in the MAP sensor circuit can cause intermittent voltage drops. Check the wiring harness for any signs of damage, such as frayed wires, cracked insulation, or corroded connectors.
• Connector Problems: Loose, corroded, or damaged connectors can interrupt the electrical signal between the MAP sensor and the ECU. Inspect the MAP sensor connector and the ECU connector for any signs of damage or corrosion.
• Vacuum Leaks: While not directly related to the electrical circuit, a significant vacuum leak can cause the MAP sensor reading to be abnormally low, potentially triggering the code. A vacuum leak will cause the engine to draw in unmetered air, affecting the manifold pressure.
• ECU Issues: In rare cases, the ECU itself may be faulty, leading to misinterpretation of the MAP sensor signal. This is the least likely cause but should be considered if all other possibilities have been ruled out.
• Poor Ground Connection: A bad ground connection can cause intermittent voltage drops. Check the ground connection for the MAP sensor circuit and ensure it's clean and secure.
• Interference: Electrical interference from other components can sometimes affect the MAP sensor signal. Inspect nearby wiring and components for potential sources of interference.

4. Common Symptoms:

• Check Engine Light: The most obvious symptom is the illumination of the Check Engine Light (CEL) on the dashboard.
• Poor Fuel Economy: The inaccurate MAP sensor signal can cause the ECU to miscalculate fuel delivery, leading to reduced fuel efficiency.
• Rough Idling: The engine may idle roughly or stall, especially when cold.
• Hesitation or Stumbling: The engine may hesitate or stumble during acceleration.
• Reduced Engine Power: The inaccurate MAP sensor signal can limit engine performance.
• Difficulty Starting: In some cases, a faulty MAP sensor can make the engine difficult to start.
• Black Smoke from Exhaust: If the engine is running rich due to the incorrect MAP sensor reading, black smoke may be visible from the exhaust.

5. Diagnostic Procedure:

1. Read the Codes: Use an OBD-II scanner to confirm the presence of the P1107 code and check for any other related codes.
2. Inspect the MAP Sensor: Visually inspect the MAP sensor for any signs of damage, such as cracks or leaks.
3. Check the Wiring: Carefully inspect the wiring harness and connectors associated with the MAP sensor for any signs of damage, corrosion, or loose connections. Use a multimeter to check the continuity of the wires and ensure there are no shorts to ground or voltage.
4. Test the MAP Sensor Voltage: With the engine running, use a multimeter to measure the voltage signal from the MAP sensor. The voltage should vary smoothly with changes in engine vacuum. Compare the readings to the manufacturer's specifications.
5. Check the MAP Sensor Ground: Ensure the MAP sensor has a good ground connection. Use a multimeter to check the resistance between the MAP sensor ground terminal and a known good ground point.
6. Check for Vacuum Leaks: Use a vacuum gauge or smoke tester to check for any vacuum leaks in the intake manifold and vacuum lines.
7. Monitor MAP Sensor Data: Use a scan tool to monitor the MAP sensor data in real-time. Look for any erratic or intermittent readings.
8. Perform a "Wiggle Test": With the engine running and the scan tool monitoring the MAP sensor data, gently wiggle the wiring harness and connectors associated with the MAP sensor. If the MAP sensor data changes significantly, it indicates a wiring or connector issue.
9. Test the MAP Sensor with a Vacuum Pump: Disconnect the MAP sensor and use a hand-held vacuum pump to apply vacuum to the sensor. Monitor the voltage output of the sensor with a multimeter. The voltage should change smoothly as the vacuum is applied.
10. Replace the MAP Sensor: If all other tests have failed to identify the problem, replace the MAP sensor with a new, known-good sensor.
11. Test the ECU (Last Resort): If all other tests have failed, and you suspect the ECU may be the problem, consult a qualified technician for further diagnosis.

6. Related Codes:

• P0105: Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction
• P0106: Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem
• P0107: Manifold Absolute Pressure/Barometric Pressure Circuit Low Input
• P0108: Manifold Absolute Pressure/Barometric Pressure Circuit High Input
• P0109: Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

Frequently Asked Questions:

• What does the P1107 code mean? The P1107 code indicates an intermittent low voltage signal from the Manifold Absolute Pressure (MAP) sensor circuit. This means the voltage is occasionally dropping below the expected range.

• Can I drive with a P1107 code? It's not recommended to drive with a P1107 code for extended periods. The engine may run poorly and fuel economy will likely suffer, potentially leading to further engine damage.

• Is the MAP sensor expensive to replace? MAP sensors are generally not very expensive, typically ranging from $30 to $100 depending on the vehicle make and model.

• Can a vacuum leak cause a P1107 code? Yes, a significant vacuum leak can cause the MAP sensor reading to be abnormally low, potentially triggering the P1107 code.

• How do I test a MAP sensor? You can test a MAP sensor using a multimeter to measure the voltage signal while applying vacuum, comparing the readings to the manufacturer's specifications.

Conclusion:

The P1107 code requires careful diagnosis to pinpoint the root cause. By systematically checking the MAP sensor, wiring, connectors, and vacuum system, you can identify and repair the issue, restoring your engine's performance and fuel efficiency. If you are not comfortable performing these diagnostic steps yourself, it is best to consult a qualified mechanic.