U0121-LOST COMMUNICATION WITH ANTI-LOCK BRAKE MODULE
For a complete wiring diagram Refer to Section 8W.
- When Monitored:
With the ignition on.
Battery voltage between 10 and 16 volts.
IOD fuse installed.
TIPM is configured correctly.
- Set Condition:
Bus messages not received from the Antilock Brake Module for approximately 2 to 5 seconds.
| Possible Causes |
| (D65) CAN C BUS(+) CIRCUIT SHORTED TO VOLTAGE |
| (D64) CAN C BUS(-) CIRCUIT SHORTED TO GROUND |
| DTCS RELATED TO BATTERY VOLTAGE, IGNITION, OR VIN MESSAGES |
| TIPM NOT CONFIGURED CORRECTLY |
| ANTILOCK BRAKE MODULE POWER AND GROUND |
| ANTILOCK BRAKE MODULE |
| MODULE THAT SET THIS DTC |
Diagnostic Test
1. VERIFY DTC IS ACTIVENOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.
With the scan tool, read active DTCs.
Is this DTC active?
Yes
- Go To 2
No
- Refer to the Stored Lost Communication test procedure. Refer to the table of contents in this section.
2. CHECK FOR ANY OF THE FOLLOWING ACTIVE DTCS
With the scan tool, read all active DTCs from all modules.
NOTE: Check for TIPM configuration, CAN C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTCs.
Does the scan tool display any active DTCs to the conditions listed above?
Yes
- Diagnose and repair the DTC. Refer to the Index for a complete list of the symptoms.
No
- Go To 3
3. VERIFY THAT THE ABS IS ACTIVE ON THE BUS
Turn the ignition on.
With the scan tool, select Network Diagnostics.
Verify that the ABS is active on the bus.
Is the ABS active on the bus?
Yes
- Go To 4
No
- Refer to the No Response test procedure. Refer to the table of contents in this section.
4. CHECK FOR ADDITIONAL COMMUNICATION RELATED DTCS
With the scan tool, select Network Diagnostics.
Is there more than one module with active DTCs “Logged Against” the ABS?
Yes
- Replace/update the Antilock Brake Module in accordance with the service information.
- Perform the appropriate VERIFICATION TEST.
No
- Go To 5
5. CLEAR DTC IN MODULE SETTING FAULT
With the scan tool, select the module setting the DTC against the ABS.
Clear active DTCs.
Is this DTC still active?
Yes
- Replace/update the module that set this DTC in accordance with the service information.
- Perform the appropriate VERIFICATION TEST.
No
- Go To 6
6. CYCLE IGNITION
Cycle the ignition from RUN to OFF three time ending with the key in the RUN position.
Does this DTC become active?
Yes
- Go To 7
No
- The condition is not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals.
- Perform the appropriate VERIFICATION TEST.
7. CHECK FOR ADDITIONAL LOST COMMUNICATION FAULTS
With the scan tool, select Network Diagnostics.
Does the TIPM and other CAN C BUS modules show Lost Communication with the remaining CAN C BUS modules?
Yes
- Go To 8
No
- Replace/update the module that set this DTC in accordance with the service information.
- Perform the appropriate VERIFICATION TEST.
8. (D65) CAN C BUS (+) CIRCUIT SHORTED TO VOLTAGE
Measure the voltage between the (D65) CAN C Bus (+) circuit and ground.
Is the voltage above 5 volts?
Yes
- Repair the (D65) CAN C Bus (+) circuit for a short to voltage.
- Perform the BODY VERIFICATION TEST – VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).
No
- Go To 9
9. (D64) CAN C BUS (-) CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Measure the resistance between ground and the (D64) CAN C Bus (-) circuit.
Is the resistance below 10K Ohms?
Yes
- Repair the (D64) CAN C Bus (-) circuit for a short to ground.
- Perform the BODY VERIFICATION TEST – VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).
No
- Replace/update the module that set this DTC in accordance with the service information.
- Perform the appropriate VERIFICATION TEST.