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Diagnostic Aids

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  1. 1) DTC 1729 Or 1781: Perform Switch Functional Check

    Turn ignition on. Observe 4x4L indicator and switch to and from 4x4L. If indicator light agrees with lever position, go to next step. If indicator light does not agree with lever position, go to step  4).

  2. 2) Check 4x4L Parameter Identification (PID)

    Ensure scan tool is connected to Data Link Connector (DLC). Using scan tool, access 4x4L PID from PID/DATA MONITOR & RECORD menu. Observe 4x4L PID reading and switch to and from 4x4L. If 4x4L PID reading agrees with lever position, go to next step. If 4x4L PID reading does not agree with lever position, go to step  11).

  3. 3) Check For Intermittent

    While observing 4x4L PID, wiggle and bend all wiring harness circuits for 4x4L. If 4x4L PID switched states (on/off) at any time, isolate fault and repair as necessary. Reconnect all connectors. Clear DTCs, and repeat QUICK TEST . If 4x4L PID did not switch states, no problem is indicated at this time. Clear DTCs, and repeat QUICK TEST .

  4. 4) Check Voltage At Switch

    Disconnect 4x4L switch 2-pin connector. Switch is located on front of transfer case. Measure voltage between ground and Light Blue/Black wire at 4x4L switch wiring harness connector. If battery voltage is present, replace 4x4L switch. Clear DTCs, and repeat QUICK TEST . If battery voltage is not present, go to next step.

  5. 5) Check Indicator Light

    Observe 4x4L indicator light and shift to and from 4x4L. If indicator light always stays on, locate and repair short to ground between indicator light and switch connector. Clear DTCs, and repeat QUICK TEST . If indicator light does not always stay on, go to next step.

  6. 6) Check Voltage At Fuse

    Measure voltage between ground and both sides of fuse No. 17 at instrument panel fuse block. If battery voltage is present at both readings, go to step  9). If battery voltage is not present at both readings, go to next step.

  7. 7) Check Power Feed To Fuse

    Measure voltage between ground and power side of No. 17 fuse holder (Red/Light Green wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open circuit in Red/Light Green wire. Clear DTCs, and repeat QUICK TEST .

  8. 8) Check For Short To Ground

    Ensure 4x4 lever is not in LOW position. Turn ignition off. Measure resistance between ground and non-powered side of No. 17 fuse holder (Red/Yellow wire). If resistance is more than 10 k/ohms, replace fuse. Clear DTCs, and repeat QUICK TEST . If resistance is 10 k/ohms or less, locate and repair short to ground in Red/Yellow wire.

  9. 9) Check 4x4L Bulb

    Turn ignition off. Remove and inspect 4x4L indicator bulb. Replace bulb as necessary. Clear DTCs, and repeat QUICK TEST . If bulb is okay, go to next step.

  10. 10) Check Voltage At Indicator Bulb

    Turn ignition on. Shift out of 4x4 Low. Measure voltage between ground and Red/Yellow wire at indicator bulb socket. If battery voltage is present, locate and repair open circuit in Light Blue/Black wire between indicator bulb and 4x4L switch. Clear DTCs, and repeat QUICK TEST .

  11. 11) Check Light Blue/Black Wire For Continuity

    Turn ignition off. Disconnect PCM 104-pin connector, and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (014-00950), leaving PCM disconnected. Disconnect 4x4L switch connector. Measure resistance between Light Blue/Black wire at 4x4L switch wiring harness connector and test pin No. 14 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, locate and repair open circuit in Light Blue/Black wire. Clear DTCs, and repeat QUICK TEST .

  12. 12) Check Light Blue/Black Wire For Short To Ground

    Measure resistance between ground and Light Blue/Black wire at 4x4L switch wiring harness connector. If resistance is less than 10 k/ohms, locate and repair short to ground in Light Blue/Black wire. Clear DTCs, and repeat QUICK TEST . If resistance is 10 k/ohms or more, replace PCM. Clear DTCs, and repeat QUICK TEST .
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