How to Use the Diagnostic Procedures

INTRODUCTION

How to Use the Diagnostic Procedures
- Use the information about the vehicle driveability or emission concerns to attempt to verify and recreate the symptom. Look for any vehicle modifications or aftermarket items that may contribute to the symptom. A check of any applicable TSBs or OASIS messages may be useful, if this information is available.
- Go to Symptom Charts, Powertrain Control Module (PCM) Quick Test. Carry out the PCM quick test. QT : Powertrain Control Module (PCM) Quick Test
- If the PCM quick test is completed, and no DTCs were retrieved, go to the No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index. No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index
- Select the symptom that best describes the vehicle symptom (for multiple symptoms select the one that is most evident). Go to the No Diagnostic Trouble Codes (DTCs) Present Symptom Charts No Diagnostic Trouble Codes (DTCs) Present Symptom Charts that is indicated. If no PCM DTCs are present and the vehicle symptom is not listed in the No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index, go to the diagnostic/repair information to continue diagnosis.
- The No Diagnostic Trouble Codes (DTCs) Present Symptom Charts contains areas to be tested for diagnosis of the vehicle symptom. The chart is arranged to place the higher probability or easiest to test items toward the top of the chart. However, the technician is not required to follow this order due to reasons such as variations in vehicle type, vehicle repair history, or technician experience.
- Follow the instructions in the step (including Preliminary Checks).
- The System or Component column indicates the areas that are tested.
- The Reference column indicates where to go for the System or Component testing. If the steps send you to a specific area for testing (for example a pinpoint test step in a diagnostic/repair information), go to the procedures. Follow the directions given in those procedures, including directions to other tests. If a concern is found, repair as directed. If no concern is found and diagnosis in that area is complete, return to the Symptom Chart and continue as directed. Symptom Related Diagnostic Procedures

- During diagnosis, if directed to test a system or component that is not contained on that vehicle, go to the next step.
- If the Symptom Chart for the vehicle symptom is completed and no concern is found, return to the Symptom Chart Index to address the next most prominent symptom. Symptom Related Diagnostic Procedures
- After any repair, reconnect all components and remove any test equipment. Verify the vehicle is operating correctly and the original complaint is no longer present. If a DTC was present, clear the DTCs and repeat the Quick Test to verify the repair.
- If a symptom is determined to be intermittent, a careful visual and physical underhood inspection of connectors, wiring harnesses, vacuum lines, and components is required. The Customer Information Worksheet may contain more detailed symptom information. Before an in-depth diagnosis begins, start the engine and wiggle wires, tap on components while listening for an indication of a concern (such as an RPM change or a relay clicking).

Information about engine conditions is stored when a DTC that illuminates the malfunction indicator lamp (MIL) is set. This information is called freeze frame data and may be helpful in diagnosing intermittent concerns. For additional information, refer to Diagnostic Methods, Freeze Frame Data. Freeze Frame Data