• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Watchdog/Safety Failure | Internal Electronic Failure |
---|---|---|---|---|
Electronic Control Unit Malfunction | -- | -- | DTC C0550 39 | DTC C0550 39 |
This DTC indicates and RAM/ROM checksum, a EEPROM failure, or an ECU malfunction due to an internal microprocessor failure.
• | The ignition is ON. |
• | System voltage is 10.5-18 volts. |
The EEPROM, RAM and ROM, and ECM Microprocessor do self checks against one another and the data does not match causing the DTC to set.
• | Shifting is still disabled until the DTC has cleared itself. |
• | The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle. |
• | The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present. |
• | A history DTC clears after 40 consecutive warm up cycles without a fault present. |
• | History DTCs can be cleared using a scan tool. |
Transfer Case Control Schematics
• | Circuit Testing |
• | Wiring Repairs |
Control Module References for scan tool information.
It is sometimes possible to set this DTC falsely due to low voltage. Attempt to clear this DTC and retest.
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for TCSCM replacement, setup, and programming |