Troubleshooting Hints - Data Link Communications

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 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 Troubleshooting Procedures.)
7. Check for proper installation of aftermarket electronic equipment which may effect the integrity of other systems. (Refer to Troubleshooting Procedures.) Diagnostic Aids