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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis 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. Inspect the engine cooling system for air flow restrictions, air flow blockage or debris. Inspect the transmission cooling system for air flow restrictions, air flow blockage, damaged cooler lines or hoses, and low transmission fluid cooler flow. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Did you perform the inspection and correct the conditions if necessary? If so, go to next step. If not, see appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  3. Check the transmission fluid level. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Is the transmission fluid level correct? If so, go to next step. If not, see appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  4. Install the scan tool. Turn ignition on, engine off. Record DTC and failure records. Start the engine. Using the scan tool, check ignition voltage. Is the voltage 9-18 volts? If not, see DTC P0562: SYSTEM VOLTAGE LOW  or DTC P0563: SYSTEM VOLTAGE HIGH  .
  5. Turn the ignition on, engine off. Using scan tool, monitor transmission fluid temperature. Start the engine and drive the vehicle under normal operating conditions or in the specific operating mode when the overtemperature condition occurred if known. Do the transmission fluid temperature readings appear inconsistent or exceed 250°F (121°C)? If so, go to next step. If not, see DIAGNOSTIC AIDS .
  6. Disconnect transmission in-line 20-way connector. Using a DVOM, measure the resistance of the TFT sensor between transmission in-line 20-way connector terminals "G" and "H". Is the resistance within the specified range? See COMPONENT RESISTANCE  under ELECTRONIC COMPONENT SPECIFICATIONS. If so, go to next step. If not, go to step  9.
  7. Reconnect the transmission in-line 20-way connector. Disconnect the TCM C2 connector. Measure the resistance between TCM connector C2 terminals No. 10 and 20. Is the resistance within the specified range? See COMPONENT RESISTANCE  under ELECTRONIC COMPONENT SPECIFICATIONS. If so, go to step  12. If not, go to next step.
  8. Inspect and repair the transmission wiring harness assembly. Is the repair complete? If so, go to step  13.
  9. Remove the pressure switch manifold. See PRESSURE SWITCH MANIFOLD  under REMOVAL & INSTALLATION. Measure the resistance between pressure manifold switch terminals "E" and "F". Is the resistance within the specified range? See COMPONENT RESISTANCE  under ELECTRONIC COMPONENT SPECIFICATIONS. If so, go to next step. If not, go to step  11.
  10. Replace the internal wiring harness. See TRANSMISSION INTERNAL WIRING HARNESS  under REMOVAL & INSTALLATION. Is the replacement complete? If so, go to step  13.
  11. Replace the pressure switch manifold. See PRESSURE SWITCH MANIFOLD  under REMOVAL & INSTALLATION. Is the replacement complete? If so, go to step  13.
    12. CAUTION: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM.
  12. Replace the TCM. See TRANSMISSION CONTROL MODULE  under REMOVAL & INSTALLATION. Is the replacement complete? If so, go to next step.
  13. Perform the following procedure to verify the repair:
    • Clear the DTC.
    • Using the scan tool, monitor the transmission fluid temperature.
    • Drive the vehicle under normal operating conditions or in the specific operating mode where the overtemperature condition occurred if known.

    Did the DTC return? If so, go to step  1. If not, system is okay.

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