Troubleshooting Hints

PERFORM BEFORE BEGINNING SYSTEM DIAGNOSIS
1. First step of Class 2 data line diagnosis should be to check for loss of Class 2 Serial Data Diagnostic Trouble Codes (DTCs) using a scan tool.
2. DTC U1300 sets if the Class 2 serial data line experiences short to ground. However, this code will never be received as current because the Class 2 bus does not function during this condition.
3. DTC U1301 sets if the Class 2 serial data line experiences short to B+. However, this code will never be received as current because the Class 2 bus does not function during this condition.
4. The Class 2 serial data line does not have a "master" controller. Communication occurs by peer-to-peer transfers. Therefore, an open circuit on one part of the Class 2 circuit typically does not cause a total loss of communication of all modules on the bus.
5. Before component replacement, check for poor terminal contact at component and harness connectors.
6. Check for a broken (or partially broken) wire inside of the insulation which could cause system failure but prove good in a continuity/voltage check. (Refer to General Troubleshooting Procedures.)
7. Check for proper installation of aftermarket electronic equipment which may effect the integrity of other systems. (Refer to General Troubleshooting Procedures.) Diagnostic Aids