Lack of communication may be because of a partial or a total malfunction of the Class 2 serial data circuit. The specified procedure determines the particular condition.

This step stores the PCM DTC information into the scan tool's memory. After you complete the diagnostic procedure, review the captured information in order to catch the next DTC if the control module stores multiple DTCs. Review the Freeze Frame data and the Failure Records data. Use this information in order to determine how frequently and how recently the DTC set. This information may help diagnose an intermittent condition. Information about the operating conditions at the time that the DTC set may also help diagnose an intermittent condition. Capturing the stored information saves the data that the PCM loses during the following conditions:

The presence of DTCs which begin with "U", indicate that some other control module is not communicating. Following the specified procedure will gather all the available information before you perform the tests.

If there are other control modules with DTCs set, refer to the DTC list. The DTC list directs you to the appropriate diagnostic procedure.

If the control module stores multiple powertrain DTCs, diagnose the DTCs in the following order:

This step is for areas that have inspection and maintenance testing procedures for emissions testing. Use this step if the testing facility found one or more I/M system statuses that did not set.