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  • P0743 Torque Converter Clutch Solenoid/Trans Relay Circuits

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    DTC P0743: TORQUE CONVERTER CLUTCH SOLENOID/TRANS RELAY CIRCUITS

    Circuit Description

    Circuit is monitored continuously while ignition is on. DTC sets if voltage detected on TCC at PCM does not match desired voltage.

    Possible Cause

    The following items may be area of concern:

    • Fused B+ feed to transmission control circuit open.
    • Transmission control relay defective.
    • TCC solenoid control circuit open.
    • TCC solenoid control circuit shorted to ground.
    • TCC wire harness defective.
    • Transmission control relay output circuit open.
    • Transmission control relay output circuit shorted to ground.
    • PCM defective.
    • DTC P1765 is set.
    • Transmission control circuit shorted to voltage.
    • Solenoid and harness assembly defective.

    Diagnostic Procedure

    1. Using scan tool, read DTCs. If good trip counter for DTC P0743 is not displayed or displayed count is not zero, go to step 16 . If good trip counter is displayed and displayed count is zero, go to next step.

    2. Using scan tool, read DTCs. If DTC P1765 is also set, see DTC P1765: TRANS 12-VOLT SUPPLY RELAY CNTRL CIRCUIT . If DTC P1765 is not set, go to next step.

    3. Using scan tool, read transmission DTCs. If DTC P0743, P0748 and P0753 are present, go to next step. If DTC P0743, P0748 and P0753 are not present, go to step 8 .

    4. Turn ignition off. Disconnect transmission solenoid harness connector. Inspect connector and terminals for damage. Repair as necessary. Turn ignition on. Using test light connected to ground, check fused transmission control relay output circuit at transmission solenoid connector terminal No. 1. If test light illuminates brightly, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. If test light does not illuminate, or does not illuminate brightly, go to next step.

    5. Turn ignition off. Remove transmission control relay from underhood Power Distribution Center (PDC) or Integrated Power Module (IPM), as applicable. Turn ignition on. Using test light connected to ground, check fused B+ circuit at transmission control relay connector terminal No. 30 (terminal C3 on AB body). If test light illuminates brightly, remove test light and go to next step. If test light does not illuminate, or does not illuminate brightly, repair circuit for open. If fuse is open, ensure to check for short to ground or
    high resistance in fused B+ circuit.

    6. Turn ignition off. Measure resistance between ground and fused transmission control relay output circuit at transmission solenoid connector terminal No. 1. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair relay output circuit for short to ground.

    7. Using fused jumper wire, jumper fused B+ circuit (terminal No. 30 (terminal C3 on AB body) and transmission control relay output circuit (terminal No. 87 (terminal C5 on AB body) together at transmission control relay connector. See WIRING DIAGRAMS . Turn ignition on. Using test light connected to ground, check fused transmission control relay output circuit at transmission solenoid connector terminal No. 1. If test light illuminates brightly, replace transmission control relay. If test light does not illuminate, or does not illuminate brightly, repair relay output circuit for open. If fuse is open, ensure to check for short to ground or high resistance in relay output circuit.

    8. Turn ignition off. Disconnect PCM harness connector C2 (White) and transmission solenoid harness connector. Measure resistance of TCC solenoid control circuit between PCM harness connector C2 (White) terminal No. 11 and transmission solenoid harness connector terminal No. 7. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair TCC solenoid control circuit for open.

    9. Measure resistance between ground and TCC solenoid control circuit at PCM harness connector C2 (White) terminal No. 11. If resistance is less than 5 ohms, repair TCC solenoid control circuit for short to ground. If resistance is 5 ohms or more, go to next step.

    10. Turn ignition on. Measure voltage of TCC solenoid control circuit. If voltage is more than .5 volt, repair TCC solenoid control circuit for short to voltage. If voltage is .5 volt or less, go to next step.

    11. Turn ignition off. Measure resistance between TCC solenoid control circuit and all other circuits at transmission solenoid connector. If resistance is less than 100 k/ohms between TCC solenoid control circuit and any other circuit, repair circuit as necessary. If resistance is 100 k/ohms or more, go to next step.

    12. Ensure ignition is off. Remove transmission control relay from underhood Power Distribution Center (PDC) or Integrated Power Module (IPM), as applicable. Measure resistance of TCC solenoid control circuit between fused transmission control relay output circuit at transmission solenoid connector terminal No. 1 and PCM harness connector C2 (White) terminal No. 11. If resistance is 25-60 ohms, go to next step. If resistance is not 25-60 ohms, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS.

    13. Measure resistance between ground and TCC solenoid control circuit at transmission solenoid connector terminal No. 7. If resistance is less than 5 ohms, repair short to ground in transmission solenoid assembly. If resistance is 5 ohms or more, go to next step.

    14. Measure resistance between TCC solenoid control circuit and governor pressure solenoid control circuit at PCM harness connector C2 (White) terminals No. 8 and 11. Resistance should be 28-68 ohms. Measure resistance between TCC solenoid control circuit and 3-4 shift solenoid control circuit at PCM harness connector C2 (White) terminals No. 11 and 21. Resistance should be 50-120 ohms. If resistance for both measurements is within specification, go to next step. If resistance is not as specified, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS.

    15. Measure resistance between TCC solenoid control circuit and all other transmission solenoid assembly circuits at appropriate PCM harness connector terminals. If resistance is less than 100 k/ohms between TCC solenoid control circuit and any other circuit, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. If resistance is 100 k/ohms or more, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.

    16. Conditions required to set DTC are not currently present. Inspect all applicable connectors and terminals for damage. Repair as necessary. If connectors and terminals are okay, see INACTIVE DTC CONDITION under SELF-DIAGNOSTIC SYSTEM. Testing is complete.


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