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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 82 (Automatic Transmission Diagnosis - ALLISON) >> Diagnostic Tests >> DTC P0731: Incorrect 1ST Gear Ratio (2002) >> Diagnostic Procedure

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. Install the scan tool. Monitor the gear ratio. Is 3.10 shown for 1st gear ratio? If so, go to next step. If not, see DIAGNOSTIC AIDS .
  5. Drive the vehicle under normal operating conditions. Using the scan tool, monitor engine, turbine, and output speed readings. Is speed sensor data erratic or are signal dropouts detected? If so, see the appropriate speed sensor DTC. If not, go to next step.
    6. 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.
  6. Conduct a clutch test for the gear range indicated by this DTC. See CLUTCH TEST  under PERFORMANCE TESTS. Did turbine speed remain at zero? If so, see DIAGNOSTIC AIDS . If not, go to next step.
  7. Remove the dipstick and inspect the transmission fluid for clutch debris or burnt odor. If necessary, drain a small amount of fluid for this inspection. Are there signs of a clutch failure? If so, go to next step. If not, go to step  9.
  8. Remove the transmission for overhaul or replacement. Is replacement complete? If so, go to step  11.
  9. Inspect for stuck or sticking trimmer valve. Was a valve problem found and repaired? If so, go to step  11. If not, go to next step.
  10. Replace solenoid "A". See SOLENOID VALVES  under REMOVAL & INSTALLATION. Is replacement complete? If so, go to next step.
  11. 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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