Pinpoint Test AN: DTC U0121:00

Four Wheel Drive (4WD) Systems - 1-Speed Torque-On-Demand

Pinpoint Tests

Pinpoint Test AN: DTC U0121:00

Normal Operation
- DTC U0121:00 (Lost Communication With Anti-Lock Brake System (ABS) Control Module: No Sub-Type Information) - sets in continuous memory in the Transfer Case Control Module (TCCM) if data messages received from the ABS module over the High Speed Controller Area Network (HS-CAN) are missing for 5 seconds or longer with ignition in RUN and battery voltage in range. For a complete list of all network messages, refer to Module Communications Network Testing and Inspection.

This pinpoint test is intended to diagnose the following:

- ABS module
- TCCM

PINPOINT TEST AN: DTC U0121:00

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AN1 VERIFY THE CUSTOMER CONCERN

- Ignition ON.
- Verify there is an observable symptom present.
- Is an observable symptom present?

Yes
GO to AN2.

No
The system is operating normally at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.

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AN2 CHECK THE COMMUNICATION NETWORK

- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Network Test.
- Carry out the network test.
- Does the ABS module pass the network test?

Yes
GO to AN3.

No
REFER to Module Communications Network Testing and Inspection.

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AN3 RETRIEVE THE RECORDED DTCs FROM THE ABS MODULE SELF-TEST

- Check for recorded DTCs from the ABS module self-test.
- Is DTC B11E8:16 (B1318) or DTC B11E8:17 (B1317) recorded?

Yes
REFER to Vehicle Dynamic Systems Testing and Inspection.

No
GO to AN4.

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AN4 RETRIEVE THE RECORDED DTCs FROM THE TCCM SELF-TEST

- Check for recorded DTCs from the TCCM self-test.
- Is DTC P0562:00 or P0563:00 recorded?

Yes
GO to Pinpoint Test A Pinpoint Test A: DTCs P0562:00 and P0563:00.

No
GO to AN5.

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AN5 RECHECK THE TCCM DTCs

NOTE: If new modules were installed prior to the DTC being set, the module configuration may be incorrectly set during the Programmable Module Installation (PMI) or the PMI may not have been carried out.

- Clear the DTCs.
- Wait 10 seconds.
- Repeat the TCCM self-test.
- Is DTC U0121:00 still present?

Yes
INSTALL a new ABS module. REFER to Vehicle Dynamic Systems Service and Repair. CLEAR the DTCs. REPEAT the TCCM self-test. If DTC U0121:00 is still present, INSTALL a new TCCM. REFER to Transfer Case Control Module (TCCM) Service and Repair. TEST the system for normal operation. REPEAT the self-test.

No
The system is operating correctly at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.

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