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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 38 (Automatic Transmission - Diagnosis [La4A-El]) >> Diagnostic Tests >> DTC P1780: O/D Off Switch Malfunction >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Mazda 626 and 2001 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.
  1. DTC P1780 indicates O/D OFF switch was not cycled during KOER self-test. Possible cause:
    • O/D OFF switch not cycled during KOER self-test.
    • O/D OFF switch circuit damage.
    • Faulty O/D OFF switch.
    • Faulty PCM.

    Repeat KOER self-test if O/D OFF switch was not cycled in original test. If O/D OFF switch was cycled during KOER self-test, go to next step.

  2. Turn ignition off. Disconnect 104-pin PCM harness connector. PCM is located behind center console. Inspect pins for damage. Install breakout box, leaving PCM disconnected. Turn ignition on. Measure voltage between breakout box test pin No. 29 (O/D OFF circuit) and test pins No. 24 and 77 (PWR GND circuit) at breakout box while cycling O/D OFF switch. If voltmeter reading does not cycle when O/D OFF switch is cycled, go to next step. If voltmeter reading cycles when O/D OFF switch is cycled, replace PCM. After repairs, go to step  6.
  3. Turn ignition off. Disconnect O/D OFF switch harness connector. Inspect pins for damage and repair if necessary. Measure resistance between breakout box test pin No. 29 (O/D OFF circuit) and test pins No. 24 and 77 (PWR GND circuit). If resistance is 10 k/ohms or more, go to next step. If resistance is less than 10 k/ohms, repair short circuit. After repairs, go to step  6.
  4. Connect ohmmeter positive lead to O/D OFF switch power at fuse panel. Connect negative lead to power terminal of O/D OFF switch wiring harness connector. Note resistance measurement. Measure resistance between breakout box test pin No. 29 (O/D OFF circuit) and O/D OFF switch signal terminal of O/D OFF switch connector. If both resistance measurements are less than 5 ohms, go to next step. If either resistance measurement is 5 ohms or more, repair open circuit. After repairs, go to step  6.
  5. Measure resistance between breakout box test pin No. 29 (O/D OFF circuit) and test pins No. 71 and 97 (VPWR circuit). If resistance is 10 k/ohms or more, replace O/D OFF switch. After repairs, go to next step. If resistance is less than 10 k/ohms, repair short circuit. After repairs, go to next step.
    6. CAUTION: On vehicles equipped with immobilizer system, reprogram ignition key identification numbers after PCM replacement. See PROGRAMMING .
  6. Disconnect breakout box. Connect all components. Erase all DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Record continuous memory DTCs and freeze frame data. Perform KOEO and KOER self-tests. See RETRIEVING DIAGNOSTIC TROUBLE CODES (QUICK TEST)  under SELF-DIAGNOSTIC SYSTEM. If DTC P1780 are still present, replace PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. If no DTCs are present but symptoms still exist, see TROUBLE SHOOTING .
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