Diagnostic System Check

DIAGNOSTIC SYSTEM CHECK - COMPUTERS AND CONTROL SYSTEMS

DESCRIPTION
The Diagnostic System Check-Computers and Controls Systems is an organized approach to identifying a condition that is created by a malfunction in the engine control system. 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 order to diagnose the concern. Understanding and correctly using the diagnostic table reduces diagnostic time and prevents the replacement of good parts.

TEST DESCRIPTION

Steps 1-2:

Steps 3-8:

Steps 9-11:

The numbers below refer to the step numbers on the diagnostic table.
2. 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.
5. 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 DTC's. 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:
- When a diagnostic procedures instructs you to clear the DTC's
- When a diagnostic procedure instructs you to disconnect the PCM connectors
- When a diagnostic procedure instructs you to replace the PCM
6. The presence of DTC's which begin with "U", indicate that some other module is not communicating. Following the specified procedure will gather all the available information before you perform the tests.
8. If there are other modules with DTC's set, refer to the DTC list. The DTC list directs you to the appropriate diagnostic procedure.If the control module stores multiple powertrain DTC's, diagnose the DTC's in the following order:
- Component level DTC's, such as sensor DTC's, solenoid DTC's, and relay DTC's- Diagnose the multiple DTC's within this category in numerical order. Begin with the lowest numbered DTC, unless the diagnostic table directs you otherwise.
- System level DTC's, for example, misfire DTC's, fuel trim DTC's, and catalyst DTC Diagnostic Trouble Code Descriptions
10. 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.