Diagnostic Instructions
DTC Descriptor
DTC C0387 59: Unable to Complete Shift Circuit/Component Protection Timeout
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Circuit/Component Timeout
|
Unable to Complete Shift
| --
| --
| --
| DTC C0387 59
|
Circuit/System Description
The transfer case control module commands shifts through motor A and motor B control circuits causing the transfer actuator to shift the transfer case to different modes or ranges depending on driver selection. The transfer case control module
monitors actuator current and incremental sensor output in order to shift the transfer case and verify that the proper position has been obtained. Deviations in current and position from expected values will cause this DTC to set.
Conditions for Running the DTC
| • | System voltage is 10.5-18 volts. |
Conditions for Setting the DTC
| • | A shift request was received but could not be completed within 15 seconds causing this DTC to set. |
| • | An incomplete shift is one that cannot reach the desired mode or range and cannot return to the original mode or range. |
| • | If the shift lever detent shaft were to bind, or there was a mechanical failure, or motor A control and motor B control were shorted together the shift would not be completed. This will cause the DTC to set in order to protect the system
components from damage. |
| • | A faulty transfer case shift control module can cause incorrect incremental sensor or motor current measurements which would also result in this DTC setting. |
| • | Intermittent motor A/B or incremental sensor circuit wiring failures can also cause this DTC to set. |
Action Taken When the DTC Sets
| • | All shifting is disabled until condition is corrected. |
| • | The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle. |
Conditions for Clearing the DTC
| • | 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. |
Reference Information
Schematic Reference
Transfer Case Control Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
Diagnostic Aids
Motor control A shorting to motor control B could cause this DTC.
Circuit/System Testing
- If either DTC C0306 or DTC C0396 is set, diagnose these DTCs first.
- Using a DMM, with the Ignition off, check to see if motor A control and motor B control are shorted together after disconnecting the transfer case control module and the transfer case actuator.
| ⇒ | If motor A control is shorted to motor B control repair the circuits as necessary. If the circuits checked good go to next step. |
- Inspect the actuator connector for damage or corrosion.
| ⇒ | If corrosion is found then repair the damage and attempt an ATC motor learn procedure. If unable to complete motor learn go to next step. |
- Replace the transfer case shift control module with known good unit and attempt an ATC motor learn.
| ⇒ | If the ATC motor learn is successful then system is OK, if not then proceed to next step. |
- Remove the transfer actuator and check to see if the shift detent shaft is binding.
| ⇒ | If the shift lever detent shaft is binding refer to
Transfer Case Disassemble
. If the shift lever detent shaft is not binding replace the transfer case actuator. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
