Flow of Diagnosis

HOW TO USE THE DIAGNOSTIC PROCEDURES

- Use information about the vehicle's driveability or emission concern to attempt a verification/recreation of the symptom(s). Look for any vehicle modifications or aftermarket items that may contribute to the symptom(s). Check Technical Service Bulletins (TSBs) that may apply.
- Go to Diagnosis By Symptom, Step 1: PCM Quick Test. Perform the Quick Test steps and follow any notes and/or directions.
- If you are not familiar with the Quick Test procedure, please review the information under Diagnostic Methods before proceding.
- If the Quick Test is completed, no Diagnostic Trouble Codes (DTCs) were received, and no Special Notes applied, follow the directions in Quick Test to Step 2: No DTC(s) Present Symptom Chart Index.
- Select the symptom that best describes the vehicle symptom. For multiple symptoms, select the one that is the most noticeable. Follow the directions to the Step 3: No DTC(s) Present Symptom Chart that is indicated.
- The No DTC(s) Present Symptom Chart contains areas to be tested for diagnosis of the vehicle's symptom(s). The chart is arranged to place the higher probability or easiest to test items toward the top of the chart. The technician, however, is not required to follow this order due to reasons such as variation in vehicle type, vehicle repair history, or technician experience.
+ The System/Component column indicates the areas that will be tested. This column may also contain a quick system/component test.
+ The Reference column indicates where to go for the System/Component testing. All references are to Pinpoint Test Steps unless noted otherwise. Follow the directions given in those procedures, including directions to other tests. If a damaged part is found, repair or replace it as directed. If no fault is found and diagnosis in that area is complete, return to the No DTC(s) Present Symptom Chart and continue as directed.
+ If a quick system/component test is in the System/Component column, the reference column will indicate where to go if the test failed.
- During diagnosis, if directed to test a system/component that is not contained on that vehicle, proceed to the next item.
- If the No DTC(s) Present Symptom Chart for the vehicle symptom is completed and no fault is found, return to Step 2: No DTC(s) Present Symptom Chart Index to address the next most prominent symptom. If all diagnosis is complete and no fault is found, it may be helpful to go to Pinpoint Test Step Z1 for further diagnosis.
- After service, restore vehicle by reconnecting components, removing test equipment, etc. Verify that the vehicle is operating properly and the original symptom is eliminated. If a DTC was present, rerun Quick Test to verify the repair and complete a PCM Reset to clear any Continuous Memory DTCs.
- If a symptom is determined to be intermittent, careful visual and physical inspection of connectors, wiring harnesses, vacuum lines, and components is required. Before an in-depth diagnosis begins, start the engine and wiggle wires, tap on components, etc., while listening for an indication of a concern (such as RPM change or relay clicking).
- Information about engine conditions is stored when a diagnostic trouble code that lights the malfunction indicator lamp is set. This information is called Freeze Frame Data and can be helpful in diagnosing intermittents.