Diagnostic System Check

DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS












Description
The Diagnostic System Check-Engine Controls 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
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.

6. This step stores the powertrain control module (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/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 DTCs.
- When a diagnostic procedure instructs you to disconnect the PCM connectors.
- When a diagnostic procedure instructs you to replace the PCM.

7. The presence of DTCs 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.

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 the control module stores multiple powertrain DTCs, diagnose the DTCs in the following order:
- Component level DTCs, such as sensor DTCs, solenoid DTCs, and relay DTCs. Diagnose the multiple DTCs within this category in numerical order. Begin with the lowest numbered DTC, unless the diagnostic table directs you otherwise.
- System level DTCs, for example, misfire DTCs, fuel trim DTCs, and catalyst DTCs.

11. 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.