How to Use the Diagnostic Procedures

HOW TO USE THE DIAGNOSTIC PROCEDURES

- Use the information about the vehicle driveability or emission concerns to attempt to verify/re-create 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, QT Step 1: Powertrain Control Module (PCM) Quick Test. Carry out the PCM quick test steps. Follow any notes as directed. QT Step 1: Powertrain Control Module (PCM) Quick Test
- If the PCM quick test is completed, no DTCs were retrieved, and no special notes applied, go to Step 2: No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index. 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 most evident). Go to the Step 3: No Diagnostic Trouble Codes (DTCs) Present Symptom Chart 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 appropriate Vehicle System to continue diagnosis. Step 3: No DTC(s) Present Symptom Charts
- The No Diagnostic Trouble Codes (DTCs) Present Symptom Charts contain 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.
- The System/Component column indicates the areas that are 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 the beginning of a pinpoint test in Pinpoint Tests unless noted otherwise. If referred to a pinpoint test in Computers and Control Systems or Vehicle Systems, go to the procedures. Follow the directions given in those procedures, including directions to other tests or Systems. If a damaged part is found, repair as directed. If no concern is found, and diagnosis in that area is complete, return to the No Diagnostic Trouble Codes (DTCs) Present Symptom Chart and continue to the next item. Step 2: No DTC(s) Present Symptom Chart Index
- If a quick system/component test is in the System/Component column, the Reference column indicates 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 step.
- If the No Diagnostic Trouble Codes (DTCs) Present Symptom Chart for the vehicle symptom is completed and no concern is found, return to Step 2: No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index to address the next most prominent symptom. If all diagnosis is complete and no concern is found, it may be helpful to GO to Pinpoint Test Z, to continue diagnosis. Step 2: No DTC(s) Present Symptom Chart Index Test Z: Intermittent
- The installation of any new component that affects the PCM adaptive learning strategies (idle speed, refueling event, or fuel trim) requires the reset of keep alive memory (KAM). Refer to Diagnostic Methods, Resetting The Keep Alive Memory (KAM). Resetting The Keep Alive Memory (KAM)
- After any repair, reconnect any components and remove any test equipment. Verify that the vehicle is operating correctly and the original complaint is no longer present. If a DTC was present, clear the DTCs and repeat the self-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. Refer to Diagnostic Methods, Freeze Frame Data for more information. Freeze Frame Data