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 ACTIVE

NOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.

Is this DTC active?

Yes

Go To 2

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

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.

Go To 3

3.VERIFY THAT THE ABS IS ACTIVE ON THE BUS

Is the ABS active on the bus?

Yes

Go To 4

Refer to the No Response test procedure. Refer to the table of contents in this section.

4.CHECK FOR ADDITIONAL COMMUNICATION RELATED DTCS

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.

Go To 5

5.CLEAR DTC IN MODULE SETTING FAULT

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.

Go To 6

6.CYCLE IGNITION

Does this DTC become active?

Yes

Go To 7

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

Does the TIPM and other CAN C BUS modules show Lost Communication with the remaining CAN C BUS modules?

Yes

Go To 8

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

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).

Go To 9

9.(D64) CAN C BUS (-) CIRCUIT SHORTED TO GROUND

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).

Replace/update the module that set this DTC in accordance with the service information.
Perform the appropriate VERIFICATION TEST.