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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 52 (Automatic Transaxle Diagnosis - 4T65-E) >> Diagnostic Tests >> DTC P1860: TCC Pulse Width Modulated Solenoid Electrical Problem >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Buick Regal, 2002 Buick Century, 2001 Buick Regal, and 2001 Buick Century. 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 DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the CLEAR INFO function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Are DTCs P0753 or P0758 also set? If so, go to next step. If not, go to step  9 .
  3. Inspect the fuse in the ignition "1" voltage circuit for an open. Replace the fuse if necessary. Was the fuse open? If so, go to next step. If not, go to step  7 .
    4. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
  4. Test the ignition "1" voltage circuit (CKT 1039) of the TCC PWM solenoid valve for a short to ground between the fuse block and the transaxle in-line 20-way connector. Did you find and correct the condition? If so, go to step  19 . If not, go to next step.
    5. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
  5. Disconnect the transaxle wiring harness from the 1-2 shift solenoid valve, the 2-3 shift solenoid valve and the TCC PWM solenoid. Test the ignition "1" voltage circuit (CKT 839) of the TCC PWM solenoid valve for a short to ground between the transaxle in-line 20-way connector and the solenoids. Did you find the condition? If so, go to step  16 . If not, go to next step.
  6. Test the 1-2 shift solenoid valve, the 2-3 shift solenoid valve and the TCC PWM solenoid valve for a short to ground between the ignition "1" voltage side of each solenoid and the transaxle case. Replace any faulty solenoid. See appropriate shift solenoid under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  19 .
  7. Test the ignition "1" voltage circuit (CKT 839) of the TCC PWM solenoid valve for an open between the fuse block and the transaxle in-line 20-way connector. Did you find and correct the condition? If so, go to step  19 . If not, go to next step.
  8. Test the ignition "1" voltage circuit (CKT 1039) of the TCC PWM solenoid valve for an open between the transaxle in-line 20-way connector and the solenoid. Did you find the condition? If so, go to step  16 . If not, see DIAGNOSTIC AIDS  .
  9. Turn ignition off. Disconnect the transaxle 20-way harness connector (additional DTCs may set). Install the Jumper Harness (J 44152) on the engine side of the transaxle in-line 20-way connector. Using the Connector Test Adapter Kit (J 35616-A), connect a test lamp from terminal "T" to terminal "E" of the jumper harness. Turn ignition on, engine off. With a scan tool, command the TCC PWM solenoid valve on and off three times. Does the test lamp turn on and off? If so, go to step  12 . If not, go to next step.
  10. Test the ignition "1" voltage circuit (CKT 1039) of the TCC PWM solenoid valve for an open between the fuse block and the transaxle in-line 20-way connector. Did you find and correct the condition? If so, go to step  19 . If not, go to next step.
  11. Test the control circuit (CKT 418) of the TCC PWM solenoid valve for an open, a short to ground or a short to power between the PCM and the transaxle in-line 20-way connector. Did you find and correct the condition? If so, go to step  19 . If not, go to step  18 .
  12. Connect the jumper harness to the transaxle side of the transaxle in-line 20-way connector. Using a DVOM, measure the resistance between terminals "T" and "E" of the jumper harness. Does the resistance measure within 10-16 ohms? If so, go to next step. If not, go to step  15 .
  13. Measure the resistance from terminals "T" and "E" to the transaxle case. Are both readings greater than 10 k/ohms? If so, see DIAGNOSTIC AIDS  . If not, go to next step.
  14. Disconnect the harness at the solenoid. Measure the resistance from each terminal of the solenoid to the transaxle case. Are both readings greater than 10 k/ohms? If so, go to step  16 . If not, go to step  17 .
  15. Disconnect the harness from the TCC PWM solenoid valve. Measure the resistance of the solenoid. Is the resistance within 10-15 ohms? If so, go to next step. If not, go to step  17 .
  16. Replace the transaxle internal wiring harness assembly. See TRANSAXLE INTERNAL WIRING HARNESS  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  19 .
  17. Replace the TCC PWM solenoid valve. See TORQUE CONVERTER CLUTCH PULSE WIDTH MODULATION SOLENOID  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  19 .
  18. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  19. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Drive the vehicle in D3 or D4 until the TCC is commanded on.
    • The TCC duty cycle must be greater than 60 percent for at least 5 seconds continuously.
    • Release the throttle to command less than 10 percent duty cycle.
    • 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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