Circuit Description
The vehicle control module (VCM) or powertrain control module (PCM) monitors the class 2 serial data circuit for communications from the transfer case shift control module. If the transfer case shift control module is unable to communicate with the VCM this DTC will set.
Conditions for Setting the DTC
No class 2 serial data from the transfer case shift control module.
Action Taken When the DTC Sets
This DTC will not illuminate the MIL.
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear after 40 consecutive warm up cycles with no failures of any non-emissions related diagnostic test. |
| • | VCM/PCM battery voltage is interrupted. |
| • | Use a scan tool. |
Diagnostic Aids
This DTC will not set unless the VCM/PCM and the transfer case shift control module have already established communications. This DTC will only diagnosis an open or intermittent connection from the transfer case shift control module to the splice.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step verifies that communication may be established between the scan tool and the transfer case shift control module.
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This step tests for any opens in the class 2 serial data circuit between the VCM and the transfer case shift control module. This step also tests for any intermittent malfunctions associated with the serial data circuit.
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Use a scan tool in order to clear and check for any DTCs in all the modules connected to the class 2 serial data circuit (the VCM/PCM, the EBCM and the transfer case shift control module).
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear DTC Information function is used. | ||||||||||||
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 4.3L | |||||||||
Does the scan tool communicate with the transfer case shift control module? | -- | |||||||||||
Inspect the class 2 serial data circuit for the following intermittent conditions:
Did you find an intermittent condition? | -- | |||||||||||
4 |
Does DTC U1026 reset? | -- | ||||||||||
5 | This DTC is intermittent. Are any additional DTCs stored? | -- | Go to the Applicable DTC | |||||||||
6 | Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||
Are any DTCs displayed? | -- | Go to the Applicable DTC | ||||||||||
