Diagnostic System Check

DESCRIPTION
The Diagnostic System Check is an organized approach to identifying a condition created by an electronic engine control system malfunction. The Diagnostic System Check must be the starting point for any driveability concern. The Diagnostic System Check directs the service technician to the next logical step in diagnosing the concern. Understanding the table and using the table correctly reduces diagnostic time and prevents the replacement of good parts.

TEST DESCRIPTION

Steps 1-3:

Steps 4-8:

Steps 9-12:

The numbers below refer to the step numbers on the diagnostic table.
2. Lack of communication may be due to a partial malfunction of the class 2 or UART serial data circuit or due to a total malfunction of the class 2 or UART serial data circuit. The specified procedure determines the particular condition.
6. This step stores the powertrain control module (PCM) diagnostic trouble code (DTC) information into the scan tools memory. Review the captured information at the end of the diagnostic procedure in order to catch the next DTC in the event there are multiple DTCs stored. Review the Freeze Frame/Failure Records data. Use this information in order to determine how frequently and how recently the DTC set. This information and other operating conditions when the DTC set may help diagnose an intermittent condition. Capturing the stored information preserves data that the PCM loses when the following occurs:
- When you are instructed to clear DTCs
- The PCM connectors are disconnected
- The PCM is replaced during a diagnostic procedure
7. The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
9. If there are other modules with DTCs set, refer to the DTC list. The DTC list directs you to the appropriate diagnostic procedure. If multiple powertrain DTCs are stored, diagnose in the following order of priority: Diagnostic Trouble Code Descriptions
- Component level DTCs Sensors, solenoids, relays etc. Multiple DTCs within this category should be diagnosed in numerical order starting with the lowest numbered DTC, unless otherwise directed.
- System level DTCs Misfire, fuel trim, catalyst etc.
11. This step is for areas that have an Inspection/Maintenance or emission testing program. The testing facility found one or more I/M system statuses not set.