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P code powertrain Medium severity

P1107 Dual Alternator Lower Circuit Malfunction/ Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent Low Voltage

The OBD2 code P1107 indicates a malfunction in the lower circuit of a dual alternator system or an intermittent low voltage issue in the Manifold Absolute Pressure (MAP) sensor circuit

Definition

The OBD2 code P1107 indicates a malfunction in the lower circuit of a dual alternator system or an intermittent low voltage issue in the Manifold Absolute Pressure (MAP) sensor circuit

Common causes

  • Faulty MAP sensor
  • Damaged wiring or connectors in the MAP sensor circuit
  • Poor ground connection
  • Short circuit in the wiring
  • Open circuit in the wiring
  • Faulty alternator or charging system issues
  • Corroded or loose electrical connections
  • Vacuum leaks affecting MAP sensor readings
  • Malfunctioning engine control module (ECM)

Common misdiagnoses

  • Faulty MAP sensor
  • Wiring issues or shorts in the MAP sensor circuit
  • Faulty alternator
  • Battery issues
  • Engine vacuum leaks
  • Faulty engine control module (ECM)
  • Corroded connectors or terminals
  • Faulty throttle position sensor (TPS)
  • Fuel pressure issues
  • Intake air temperature sensor problems

Troubleshooting steps

  1. 1. Check the Basics

    Battery Voltage: Ensure the battery is fully charged and in good condition. A weak battery can cause low voltage issues

  2. 2. Connections

    Inspect battery terminals and ground connections for corrosion or looseness

  3. 3. Inspect the MAP Sensor

    Visual Inspection: Check the MAP sensor for physical damage, loose connections, or corrosion at the connector

  4. 4. Wiring

    Inspect the wiring harness for frays, breaks, or shorts that could affect the signal

  5. 5. Connector

    Ensure the connector is securely attached and free of debris

  6. 6. Test the MAP Sensor

    Voltage Test: Use a multimeter to check the voltage at the MAP sensor connector. Compare the readings to the specifications in the vehicle’s service manual

  7. 7. Signal Test

    With the engine running, monitor the MAP sensor output voltage. It should change with engine vacuum. If it remains constant or is out of range, the sensor may be faulty

  8. 8. Check the Alternator

    Output Voltage: Test the output voltage of the alternator with the engine running. It should typically be between 13.5 to 14.5 volts

  9. 9. Connections

    Inspect the alternator connections and wiring for damage or corrosion

  10. 10. Dual Alternator System

    If applicable, ensure both alternators are functioning correctly and that the wiring between them is intact

  11. 11. Inspect the Ground Connections

    Ground Points: Check all ground connections related to the MAP sensor and alternator. A poor ground can lead to low voltage issues

  12. 12. Continuity Test

    Perform a continuity test on ground wires to ensure they are not broken

  13. 13. Scan for Additional Codes

    Check for Other Codes: Use an OBD-II scanner to check for any other related trouble codes that may provide additional context for the issue

  14. 14. Clear Codes and Test Drive

    Clear Codes: After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code returns

  15. 15. Professional Help

    If the issue persists after following these steps, consider seeking help from a professional mechanic who can perform more advanced diagnostics. By following these steps, you should be able to identify the root cause of the P1107 code and take appropriate action to resolve the issue