Lexus OBD-II Error Code P1172

Lexus OBD-II Major Transmission

Model: OBD-II | Code: P1172

Applicable Systems
IS ES RX GX LX LC

Symptoms

The TCM has detected a manufacturer-specific transmission fault. The transmission may default to limp mode. DTC P1172 is stored in the Lexus engine control module.

Possible Causes

  • Transmission solenoid fault
  • Transmission fluid temperature high
  • Gear ratio incorrect
  • TCM internal fault

Troubleshooting Steps

  1. Step 1: Connect an OBD-II scanner and read DTCs to confirm P1172
    DTC P1172 present with freeze frame data
  2. Step 2: Inspect wiring and connectors in the affected circuit for damage, corrosion, or loose pins
    Wiring intact, connectors clean and seated
  3. Step 3: Perform component-level testing per manufacturer service manual
    Component values within spec or component confirmed faulty
  4. Step 4: Repair or replace the faulty component, clear DTC, and verify no return
    DTC cleared and does not return after a road test

How to Reset

Clear the DTC after repair using a diagnostic scanner. The code clears automatically if the fault is not detected for 3 consecutive drive cycles.

Common Replacement Parts

  • varies: Diagnose and replace the confirmed faulty component (Confirm part number via VIN at a Lexus dealership)

Frequently Asked Questions

  • Q: What does P1172 mean?

    This manufacturer-specific DTC indicates a transmission system fault. Refer to the vehicle's service manual for the exact diagnostic procedure.

  • Q: Can I drive with P1172?

    Limited driving is possible, but the affected system may not operate correctly. Have the vehicle diagnosed promptly to prevent potential damage.

Related Lexus Fault Codes

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Source: SAE J2012 Lexus Manufacturer-Specific DTC

Category: OBD-II