Diagnostic Troubleshooting Strategy

Use these steps to plan your diagnostic strategy. If you follow them carefully, you will be sure that you have exhausted most of the possible ways to find an HBB fault.

1. Gather information about the problem from the customer.
2. Verify that the condition described by the customer exists.
3. Check for any HBB DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  .
4. If you cannot verify the condition and no HBB DTC sets, it can be assumed that the malfunction is intermittent.
5. If you can verify the condition but no HBB DTC sets, or the system cannot communicate with the scan tool, check that the basic brake system is operating properly.
   • If the basic brake system is not operating properly, diagnose and repair basic brake system. See DISC article.
   • If the basic brake system is operating properly, diagnose and repair by symptom. See SYMPTOM INDEX  table under SYSTEM TESTS.
6. If an HBB DTC sets, record the number of DTCs, then erase DTCs from memory using the scan tool. See CLEARING DIAGNOSTIC TROUBLE CODES  .
7. Duplicate the HBB DTC set conditions to see if the same HBB DTC will set again. See DTC SET CONDITIONS in appropriate DTC test.
   • If the same HBB DTC sets again, perform the diagnostic procedures for the DTC. See DTC DEFINITION  table under RETRIEVING DIAGNOSTIC TROUBLE CODES.
   • If you cannot make the same HBB DTC set again, it can be assumed that the malfunction is intermittent.