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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. 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.
  3. Install the scan tool. Turn ignition on, engine off. Record the DTC failure records. Start the engine. Using the scan tool, check ignition voltage. Is the voltage 9-18 volts? If so, go to next step. If not, see DTC P0562: SYSTEM VOLTAGE LOW  or DTC P0563: SYSTEM VOLTAGE HIGH  .
  4. Using the scan tool, check input speed and output speed to verify that the speed sensors are functioning correctly. Were the speed sensors functioning incorrectly? If so, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  under SELF-DIAGNOSTIC SYSTEM. If not, go to next step.
  5. Drive the vehicle under normal operating conditions. Using the scan tool, monitor pressure switch "C", "D", and "E" status. Refer to pressure switch manifold logic. See Figure. Does the scan tool indicate the correct pressure switch status for each range? If so, go to next step. If not, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  under SELF-DIAGNOSTIC SYSTEM.
  6. Using the scan tool, monitor the gear ratio. Is the gear ratio 3.10:1? If so, go to next step. If not, see DIAGNOSTIC AIDS .
    7. CAUTION: When using the scan tool to perform a clutch test in 4th or 5th gear, never exceed 1400 RPM under stall conditions (with brakes held), or transmission damage may occur.
  7. Connect the pressure gauge to the line pressure tap. See HYDRAULIC PRESSURE TESTS  under PERFORMANCE TESTS. Using the scan tool in clutch test mode, select each forward gear range and check line pressure at 600 RPM and 1400 RPM. Is line pressure consistent with the pressure schedule specifications? If so, go to step  10. If not, go to next step.
  8. Is line pressure low in all gear ranges? If so, see SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING. If not, go to next step.
  9. Is line pressure low only in 1st gear or significantly lower in 1st gear than in any other gear? If so, go to step  11. If not, see SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING.
  10. Remove the oil pan. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Inspect the pan for contamination. Inspect the control valve body for sticking valves. Was a condition found and repaired? If so, go to step  12. If not, see SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING.
  11. Inspect for pressure loss in the following areas:
    • Shift Solenoid Seals
    • Valve Body Gaskets
    • Valve Body Passages
    • C1 And C5 Piston Seals

    Was a condition found and repaired? If so, go to next step. If not, see SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING.

  12. Perform the following procedure to verify the repair:
    • Clear the DTC.
    • Operate the vehicle in all gear ranges under normal driving conditions.

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

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