Reading Diagnostic Trouble Codes

TEST DESCRIPTION

Diagnostic Chart:

The numbers below refer to the step numbers on the diagnostic table.
2. The diagnostic tables in this system are designed for use with a scan tool. If the scan tool is inoperative, this condition must be corrected before beginning any other diagnostic procedures. DO NOT clear the DTCs unless you are instructed to do so by a diagnostic procedure.
5. Checking for applicable service bulletins before proceeding with diagnosis is recommended.
6. If any multiple DTCs are stored, diagnose in the following order of priority:
- The ECM DTCs, P0601, P0602, P0603, P0604 or P0606
- The system voltage DTCs
- The component level DTCs-the sensors, the solenoids, the relays etc.-The multiple DTCs within this category should be diagnosed in numerical order starting with the lowest numbered DTC.
- The system level DTCs-the Misfire, the fuel trim, etc.
- The transmission DTCs-The transmission DTCs are not located in this system. Refer to A Transmission On Board Diagnostic (OBD) System Check for transmission DTC diagnosis.

When there is a known exception, a DTC table may direct the technician to diagnose a different DTC first.

7. Capturing the stored information will preserve the data that will be lost when you are instructed to clear the DTCs at the end of a diagnostic table, or if an ECM disconnect occurs during a diagnostic procedure. The Freeze Frame data stores in the scan tools memory. Any non-emissions DTCs that are set should be written down at this time. The Freeze Frame only stores data for the emissions related DTCs. The captured information should be reviewed at the end of the diagnostic table in order to catch the next DTC in the event that multiple DTCs were stored. Follow the order of the priority as listed above.