Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 1. A DTC U1001-U1254 "Lost Communications with XXX" with a history status may indicate the cause of U1000 or U1255.
- 2. The modules not communicating are the likely cause of U1000 or U1255. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.
- 7. The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001 - U1254 "Lost Communications with XXX" for those modules that it was monitoring.
- 9. The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.
- 12. If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.
- 14. The module which set U1000 or U1255 is the likely cause of the malfunction.
Scheme 36
Scheme 37
The number below refers to the step number on the diagnostic table.
- 8. The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.
Scheme 38
Scheme 39
The number below refers to the step number on the diagnostic table.
- 4. If the battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool.
Scheme 40
The numbers below refer to the step numbers on the diagnostic table.
- 2. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit.
- 3. The following DTCs may be retrieved with a history status. These DTCs are not the cause of the present condition. U1300 U1301 U1305
- 8. A State of Health DTC with a history status may be present along with a U1000 or U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
- 10. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
- 12. An open between the DLC and the class 2 serial data circuit will prevent the scan tool from communicating with any module. This condition will not set a DTC.
- 13. Splitting the class 2 serial data circuit will help isolate the location of the malfunction. If communication can be established, the malfunction is located in the wiring or one of the modules that is no longer connected to the DLC. If communication cannot be established, the malfunction is located in the wiring or one of the modules that is still connected to the DLC.
- 21. If there are no current DTCs that begin with the letter "U", the communication malfunction has been repaired.
- 22. The communication malfunction may have prevented diagnosis of the customer complaint.
