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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 69 (Automatic Transmission Diagnosis - 4L80-E (Diesel)) >> Diagnostic Tests >> DTC P1860: TCC PWM Solenoid Circuit - Electrical Malfunction >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Cab & Chassis Sierra 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. Install a scan tool. Turn ignition on, engine off. Before clearing the DTC, use the scan tool to record the freeze frame and failure records. Using the CLEAR INFO function erases the freeze frame and failure records from the PCM. Record the DTC freeze frame and failure records. Clear the DTC. If DTCs P0753 or P0758 are also set, inspect the fuse. Is the fuse open? If so, go to next step. If not, go to step  4 .
  3. Inspect the voltage circuit (1020), the three solenoids and the transmission wiring harness assembly for a short to ground. Did you find and correct the condition? If so, go to step  17 . If not, see DIAGNOSTIC AIDS  .
  4. Turn ignition off. Disconnect the transmission in-line 20-way connector. Additional DTCs may set. Install the Jumper Harness (J-44152) on the engine side of the 20-way connector. Turn ignition on, engine off. Connect a test light from jumper harness terminal "E" to a good ground. Does the test light illuminate? If so, go to step  6 . If not, go to next step.
  5. Repair the open or high resistance in the TCC PWM solenoid valve voltage circuit (1020) between the instrument panel fuse block and the transmission in-line 20-way connector. Did you complete the repair? If so, go to step  17 .
  6. Install the test light from jumper harness terminal "E" to terminal "S". Use the scan tool OUTPUT CONTROL function to command the TCC PWM solenoid valve on and off three times. Does the test light illuminate when the TCC PWM solenoid valve is command on, and turn off when commanded off? If so, go to step  8 . If not, go to next step.
  7. Test the TCC PWM solenoid valve control circuit (418) for an open or short to ground between the PCM connector C3 terminal C5 and the transmission in-line 20-way connector. Did you find and correct the condition? If so, go to step  17 . If not, go to step  9 .
  8. Install the jumper harness on the transmission side of the 20-way connector. Using a DVOM and the Connector Test Adapter Kit (J-35616-A), measure the resistance between terminals "E" and "S". Does the resistance measure 10-15 ohms? If so, go to step  11 . If not, go to step  10 .
  9. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17 .
  10. Disconnect the transmission wiring harness at the TCC PWM solenoid valve. Measure the resistance of the TCC PWM solenoid valve. Does the resistance measure 10-15 ohms? If so, go to step  12 . If not, go to step  15 .
  11. Test the resistance between terminal "E" and a good ground. Test the resistance between terminal "S" and a good ground. Do both readings measure greater 250 k/ohms? If so, see DIAGNOSTIC AIDS  . If not, go to step  13 .
  12. Test the automatic transmission internal wiring harness assembly for an open circuit. Was an open condition found? If so, go to step  16 .
  13. Disconnect the wiring harness at the TCC PWM solenoid valve. Measure the resistance between each of the component terminals and a good ground. Do both readings measure greater 250 k/ohms? If so, go to next step. If not, go to step  15 .
  14. Test the transmission internal wiring harness assembly for a short to ground. Was a short to ground condition found? If so, go to step  16 .
  15. Replace the TCC PWM solenoid valve. See SOLENOID VALVES  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17 .
  16. Replace the transmission internal wiring harness assembly. See TRANSMISSION INTERNAL WIRING HARNESS  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  17. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Select the parameters: TCC DUTY CYCLE, TCC DUTY CYCLE OPEN/SHORTED TO GND and TCC DUTY CYCLE SHORTED TO VOLTS.
    • Operate the vehicle.
    • The TCC PWM solenoid valve is commanded on and TCC DUTY CYCLE SHORTED TO VOLTS is "NO".
    • The TCC PWM solenoid valve is commanded off and TCC DUTY CYCLE OPEN/SHORTED TO GND is "NO".
    • Each condition is met for 5 seconds.
    • Select SPECIFIC DTC.
    • Enter DTC P1860.

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

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