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 , Powertrain Control Module (PCM)/Secondary On board Diagnostic Module C (SOBDMC) Quick Test. Carry out the Quick Test steps. Follow any notes as directed.
• If the Powertrain Control Module (PCM)/Secondary On board Diagnostic Module C (SOBDMC) Quick Test is completed, no DTCs were retrieved, and no special notes applied, go to the 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 noticeable). Go to the NO DIAGNOSTIC TROUBLE CODES (DTCS) PRESENT SYMPTOM CHARTS as indicated. If no PCM or SOBDMC DTCs are present and the vehicle symptom is not listed in the No Diagnostic Trouble Code (DTC) Present Symptom Chart Index, go to the appropriate Service Information article to continue diagnosis.
• The No Diagnostic Trouble Code (DTC) Present Symptom Chart 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. The technician, however, 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 pinpoint test steps in Pinpoint Tests of this article unless noted otherwise. If referred to a pinpoint test step in this article or a Service Information article, go to the procedures. Follow the directions given in those procedures, including directions to other tests or article. 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 CHARTS to continue to the next item.
  • If a quick system/component test is in the System/Component column, the reference column indicates where to go if the test is not passed.
• If the No Diagnostic Trouble Code (DTC) Present Symptom Chart for the vehicle symptom is completed and no concern is found, return to the 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, go to Pinpoint Tests , Pinpoint Test Z to continue diagnosis.
• The installation of any 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 RESETTING THE KEEP ALIVE MEMORY (KAM) .
• After repair, restore the vehicle by reconnecting any components and removing test equipment. Verify the vehicle is operating correctly and the original complaint is eliminated. If a DTC was present, repeat the Quick Test to verify the repair and clear the continuous PCM and SOBDMC DTCs.
• If a symptom is determined to be intermittent, 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 and tap on components while listening for an indication of a concern (such as an RPM change or a relay clicking).

The information called freeze frame data can be stored when the PCM or SOBDMC DTC is present. This information can be helpful in diagnosing intermittent concerns. Refer to FREEZE FRAME DATA , for more information.