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P1908 Transmission Pressure Circuit Solenoid Open or Short to Ground

The OBD2 code P1908 indicates a malfunction in the transmission pressure circuit, specifically that there is an open circuit or a short to ground in the solenoid responsible for regulating transmission fluid pressure

Definition

The OBD2 code P1908 indicates a malfunction in the transmission pressure circuit, specifically that there is an open circuit or a short to ground in the solenoid responsible for regulating transmission fluid pressure

Common causes

  • Faulty transmission pressure solenoid
  • Damaged wiring or connectors
  • Short circuit in the wiring harness
  • Open circuit in the wiring harness
  • Faulty transmission control module (TCM)
  • Poor ground connection
  • Corrosion at electrical connectors
  • Internal transmission failure

Common misdiagnoses

  • Faulty Transmission Control Module (TCM)
  • Wiring issues or shorts in the harness
  • Faulty transmission pressure sensor
  • Incorrect fluid levels or quality
  • Faulty solenoid pack
  • Transmission fluid leaks
  • Internal transmission damage
  • Electrical connector issues

Troubleshooting steps

  1. 1. Check the Vehicle's Service Manual

    Refer to the specific service manual for your vehicle to understand the wiring diagrams, solenoid specifications, and any specific procedures related to the transmission pressure circuit

  2. 2. Visual Inspection

    Wiring and Connectors: Inspect the wiring harness and connectors related to the transmission pressure solenoid for any signs of damage, corrosion, or loose connections

  3. 3. Solenoid Condition

    Check the solenoid itself for any physical damage or signs of wear

  4. 4. Check for Additional Codes

    Use an OBD-II scanner to check for any other related trouble codes that may provide more context to the issue

  5. 5. Test the Solenoid

    Resistance Test: Disconnect the solenoid connector and use a multimeter to measure the resistance of the solenoid. Compare the reading to the specifications in the service manual. If the resistance is out of range, the solenoid may be faulty

  6. 6. Power and Ground Test

    With the connector still disconnected, check for power and ground at the solenoid connector while the vehicle is in the appropriate mode (e.g., ignition on, engine running). Ensure that the correct voltage is present

  7. 7. Check for Shorts or Opens in the Wiring

    Continuity Test: Perform a continuity test on the wiring between the transmission control module (TCM) and the solenoid. Look for any breaks or shorts in the wiring

  8. 8. Ground Test

    Check for proper grounding of the solenoid circuit. A poor ground can cause the solenoid to malfunction

  9. 9. Inspect the Transmission Control Module (TCM)

    If the solenoid and wiring are in good condition, the issue may lie within the TCM. Check for any signs of damage or malfunction

  10. 10. If possible, reprogram or reset the TCM to see if that resolves the issue

  11. 11. Check Fluid Levels and Condition

    Ensure that the transmission fluid is at the correct level and in good condition. Low or contaminated fluid can affect solenoid operation

  12. 12. Clear the Code and Test Drive

    After performing repairs or replacements, clear the trouble code using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  13. 13. Professional Diagnosis

    If the issue persists after following these steps, it may be necessary to consult a professional mechanic or technician who has access to advanced diagnostic tools and equipment.Conclusion By following these troubleshooting steps, you can systematically identify and address the cause of the P1908 code. Always ensure safety precautions are taken when working on a vehicle, and consult a professional if you are unsure about any step in the process