C0398
DTC C0398
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC C0398 5A
- Incremental Sensor - Rotational Position Sensor Correlation Plausibility Failure
Typical Scan Tool Data
Circuit/System Description
The transfer case incremental position sensor (IPS) and the transfer case two/four wheel drive actuator position sensor, also known as the rotational position sensor (RPS), both send transfer case mode/range position information to the transfer case shift control module (TCCM). Both sensors send this information as voltage signals which are converted to degrees by the TCCM software. If the two sensors disagree by greater than a predetermined amount the DTC will set.
The IPS is more sensitive than the RPS, but needs to reference the RPS value at key-up and mode changes. The IPS is an integral part of the transfer case actuator and cannot be replaced independently.
The RPS is an absolute sensor and is an independently replaceable part. The TCCM syncs the IPS with the RPS at key-up and mode changes.
Conditions for Running the DTC
* Ignition ON.
* System voltage 10.5-18 V.
Conditions for Setting the DTC
The incremental sensor and the rotational position sensor are both showing valid positions, but differ by greater than a predetermined amount when NO mode change is in progress.
Action Taken When the DTC Sets
* Shifting disabled.
* The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.
Conditions for Clearing the DTC
* The TCCM clears the DTC once the conditions for setting the DTC are no longer present.
* A history DTC clears after 40 consecutive warm up cycles without a fault present.
* History DTCs can be cleared using a scan tool.
Diagnostic Aids
* The incremental position sensor and the rotational position sensor both show position in degrees. Monitor these parameters for erratic or unreasonable readings.
* A Key ON, engine OFF sequence with transfer case encoder motor removed, but still attached to the harness, will cause C0398 5A to set.
Reference Information
Schematic Reference
Transfer Case Control Schematics (MP 3023/3024-NQH - Transfer Case)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information.
Circuit/System Verification
1. Key ON, engine OFF.
2. Connect a scan tool.
3. Monitor the IPS and RPS parameters on the scan tool. Using the transfer case shift control switch, shift the transfer case into all modes. The IPS and RPS parameters should track each other.
Circuit/System Testing
1. If DTC C0392 (RPS) or C0396 (IPS) is set, diagnose it first.
2. Go to Component Testing.
Component Testing
Note: Order of component testing is important.
1. Rotational Position Sensor (RPS)
1. Key OFF. Disconnect the RPS X1 connector. Remove the RPS. Inspect the mating surface for damage. Replace if damage is found.
2. Rotate the RPS sensor tab to the lock position. Reconnect the RPS.
3. Key ON, engine OFF.
4. While monitoring the RPS parameter on the scan tool, push in the locking tab and rotate the RPS sensor tab. In the lock position the RPS parameter should read 25-45°. Upon rotating the RPS tab, the RPS parameter should display a sweep from -146 to +204 degrees.
• If the RPS parameter does not display as described, replace the RPS.
5. Using a wide, flat blade screwdriver in the RPS mounting slot, attempt to rotate the transfer case control actuator shaft. The shaft should not turn.
• If the shaft can be turned, then internal damage has occurred to the transfer case control actuator shaft or mating gears. Refer to transfer case disassemble and inspection, and repair as necessary.
2. Transfer Case Encoder Motor (TCEM) - Incremental Position Sensor
1. Remove the TCEM from transfer case. Using a paint pen or marker, place indexing marks on the encoder motor drive gear and the mounting surface of the encoder motor.
2. Attach the TCEM to the TCEM connector.
3. Key ON, engine OFF.
Note: Pressing the exit button on the scan tool between commanding the Transfer Case Motor Control forward and reverse is critical to proper diagnosis. Pressing the exit button changes the commanded state to NONE. If you DO NOT press the exit button between changing directions, the Incremental Position Sensor parameter may not update. When this happens you have to command the new direction a second time in order for the scan tool to update. Repeatedly changing directions may cause the Incremental Position Sensor parameter to flip extremes, -150° to +360° / +360° to -150°.
4. While monitoring the Incremental Position Sensor parameter, command the TCEM forward using the Transfer Case Motor Control function of the scan tool. After 10 seconds the Incremental Position Sensor parameter should read -150° or +360°. Push the exit button on the scan tool once to return the commanded state to NONE. Command the TCEM reverse. After 10 seconds the Incremental Position Sensor should read +360° or -150°.
• If the Incremental Position Sensor parameter does not display as described, repeat step 4. If the Incremental Position Sensor parameter continues to not display as described, replace the TCEM.
5. Key OFF. Install the TCEM.
6. Key OFF for at least 3 minutes.
7. Key ON, engine OFF. The TCCM should relearn the TCEM position and the Transfer Case Position parameter should display a valid mode.
• If the Transfer Case Position parameter displays Invalid, perform the Transfer Case High/Low Clutch Reset (Transfer Case High/Low Clutch Reset) procedure.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Transfer Case Disassemble (Transfer Case Disassemble)
* Transfer Case Two/Four Wheel Drive Actuator Replacement (Transfer Case Two/Four Wheel Drive Actuator Replacement)
* Transfer Case Two/Four Wheel Drive Actuator Position Sensor Replacement (Transfer Case Two/Four Wheel Drive Actuator Position Sensor Replacement)
* Transfer Case High/Low Clutch Reset (Transfer Case High/Low Clutch Reset)