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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 Chevrolet Suburban, and 2002 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Perform the transmission fluid checking procedure. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Was the fluid checking procedure performed? If so, go to next step. If not, see appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  3. Install a scan tool. Turn ignition on, engine off. Before clearing the DTCs, use the scan tool to record the failure records. Using the CLEAR INFO function erases the failure records from the PCM. Record the failure records. Clear the DTCs. Does the scan tool indicate that the TFT sensor signal voltage is less than 0.14 volt? If so, go to next step. If not, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect the transmission in-line 20-way harness connector. Multiple DTCs may set. Turn ignition on, engine off. Does the scan tool indicate that the TFT sensor signal voltage is greater than 4.92 volts? If so, go to next step. If not, go to step  9.
  5. Turn ignition off. Install the Jumper Harness (J-44152) on the transmission side of the transmission in-line 20-way connector. Using a DVOM and the Connector Test Adapter Kit (J-35616-A), measure the resistance between jumper harness terminals "L" and "M". Does the resistance measure within 16 k/ohms at 14°F (-10°C) to 133 ohms at 230°F (110°C)? If so, go to next step. If not, go to step  7.
  6. Measure the resistance between terminal "L" and a good ground on the transmission case. Does the resistance between terminal "L" and any other terminal measure less than 50 k/ohms? If so, go to next step. If not, see DIAGNOSTIC AIDS .
  7. Disconnect the TFT sensor from the transmission wiring harness. Measure the resistance between terminal "L" and all other terminals of the jumper harness. Does the resistance measure less than 50 k/ohms? If so, go to step  10. If not, go to next step.
  8. Replace the TFT sensor. See TFT SENSOR  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  12.
  9. Test the TFT sensor signal circuit (1227) for a short to ground. Did you find and correct the condition? If so, go to step  12. If not, go to step  11.
  10. Replace the transmission internal wiring harness assembly. See TRANSMISSION INTERNAL WIRING HARNESS  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  12.
  11. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  12. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Be sure the TFT sensor indicates a voltage greater than 0.16 volt for 15 seconds.
    • Select SPECIFIC DTC.
    • Enter DTC P0712.

    Has the test run and passed? If so, system is okay. If not, go to step  1.

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