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DTC Troubleshooting

DIAGNOSIS PROCEDURE - DTC U0121 CAN COMMUNICATION ERROR (NO MESSAGE FROM ABS MODULE)

Step Action Value(s) Yes No
1 Perform an On-Board Diagnostic (OBD) System Check.
Is the system check complete?		 - Go to Step 2. Go to "ON-BOARD DIAGNOSTIC (OBD II) SYSTEM CHECK ".
2
  1. Turn the ignition switch to LOCK.
  2. Install the scan tool to the Data Link Connector (DLC).
  3. Turn the ignition switch to ON.

Are any Diagnostic Trouble Codes (DTCs) displayed?		 - Go to Step 3. Try with another scan tool
3 Refer to the applicable DTC TABLE . Start with the DTC with the lowest numerical value and move up.
Is the DTC identified as valid trouble code U0121?		 - Go to Step 4. Go to applicable DTC TABLE .
4
  1. Turn the ignition switch to LOCK.
  2. Disconnect the Engine Control Module (ECM) and the ABS module.
  3. Check for an open or a short to ground in the wire between the CAN high of ABS module and ECM connector terminal 41.

Is the problem found?		 - Go to Step 6. Go to Step 5.
5 Check for an open or short to ground in the wire between the CAN low of ABS module and ECM connector terminal 22.
Is the problem found?		 - Go to Step 6. Go to Step 7.
6
  1. Change the unshielded twisted pair between ABS module and ECM or repair the connector terminal as needed.
  2. Using the scan tool, clear the DTCs.
  3. Start the engine and idle at normal operating temperature.
  4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?		 - Go to Step 9. Go to Step 2.
7
  1. Replace the ABS module.
  2. Using the scan tool, clear the DTCs.
  3. Start the engine and idle at normal operating temperature.
  4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?		 - Go to Step 9. Go to Step 8.
8
  1. Replace the ECM.
  2. Using the scan tool, clear the DTCs.
  3. Start the engine and idle at normal operating temperature.
  4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?		 - Go to Step 9. -
9 Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?		 - Go to applicable DTC TABLE . System OK
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