Section 2: Diagnostic Methods

Introduction 0-3

Introduction

Section 2: Diagnostic Methods

This section contains information on specific diagnostic tasks that are used during diagnosis. Descriptions of specific diagnostic methods are included, as well as detailed instructions on how to access or carry out the task.

Section 3: Symptom Charts

All diagnosis begins in Section 3 with QT Powertrain Control Module (PCM) Quick Test. If the PCM Quick Test is completed and no diagnostic trouble codes (DTCs) have been retrieved, the technician is directed to the No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index in Section 3. The No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index contains the list of symptoms addressed in this manual, and directs the technician to the appropriate chart in the No Diagnostic Trouble Codes (DTCs) Present Symptom Charts. If no PCM DTCs are present and the vehicle symptom is not listed in the No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index, the technician should go to the appropriate Workshop Manual section to continue diagnosis.

Section 4: Powertrain Diagnostic Trouble Code (DTC) Charts and Descriptions

This section contains the Diagnostic Trouble Code (DTC) Charts and Descriptions. These charts and descriptions are referenced if a DTC is retrieved in Section 3. Also included in this section is the list of possible causes and diagnostic aids.

Section 5: Pinpoint Tests

All pinpoint tests are included in this section. Never enter a pinpoint test unless directed there. When directed to a pinpoint test, always read the information included at the beginning of the pinpoint test.

Section 6: Reference Values

This section contains the Typical Diagnostic Reference Values charts. The technician is directed to these charts from Pinpoint Test Z in Section 5.

How to Use the Diagnostic Procedures

• Use the information about the vehicle driveability or emission concerns to attempt to verify/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 Section 3, GO to Quick Test QT1 Powertrain Control Module (PCM) Quick Test. Carry out the PCM quick test steps. Follow any

notes as directed.

• If the PCM 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 evident). Go to the No

Diagnostic Trouble Codes (DTCs) Present Symptom Charts as 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 Workshop Manual section to continue diagnosis.

• 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

Section 5 of this manual unless noted otherwise. If referred to a pinpoint test in this manual or a Workshop Manual section, go to the procedures. Follow the directions given in those procedures, including directions to other tests or sections. 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 failed.

• During diagnosis, if directed to test a system/component that is not contained on that vehicle, go 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 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, it may be helpful to GO to Pinpoint Test Z in Section 5 to continue diagnosis.

• The installation of any new component that affects the PCM adaptive learning strategies (adaptive airflow, idle speed, refueling event, or

fuel trim) requires the reset of keep alive memory (KAM). Refer to Section 2, Resetting The Keep Alive Memory (KAM) to reset the KAM.

• After any repair, reconnect any 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 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 a RPM change or a relay clicking).

2016 Powertrain Control/Emissions Diagnosis, Gasoline Engines, 3/2015