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Will Not Shift Between 2HI & 4HI Modes

  1. Check TCCM for stored codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES . If any DTCs are present, go to appropriate DTC test. If no DTCs are present, go to next step.
  2. Test drive to confirm 2WD to 4WD mode change does not operate. Disconnect TCCM harness connector and check for corrosion and damage. Repair replace as necessary. Reconnect all electrical components. Turn ignition on. Measure voltage at TCCM harness connector terminal No. C4. See Figure. Measure voltage at TCCM harness connector terminal No. C4. If battery voltage does not exist, go to next step. If battery voltage exists, repair suspect wire for short to battery power.
  3. Turn ignition on. Measure voltage at TCCM harness connector terminal No. C4 and C5 while pressing 4HI and 2HI buttons. if battery voltage exists when corresponding button is pressed, go to next step. If battery voltage does not exist when corresponding button is pressed, go to step 5).
  4. Measure resistance between TCCM harness connector terminals No. C10, D10, D12, D13 (Black wires) and ground. If resistance is greater than 2 Ohms, repair open suspect ground [Black) wire. If resistance is less than 2 ohms, replace TCCM.
  5. Measure resistance of Gray/Black wire and White wire between TCCM harness connector terminals No. C4 and C5 and 4WD selector switch harness connector. If resistance of either circuit is greater than one ohms, repair open circuit as necessary. If both circuits are one ohm or less, replace 4WD selector switch.
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