- Flow of Diagnosis - Start Here

Flow Of Diagnosis:

Flow of Diagnosis
The flow of diagnosis is the where to start when diagnostics are necessary. The steps that the technician should follow are outlined below:
Review The Driveability And Repair History Worksheets
These worksheets are to be filled out by the customer when the vehicle is brought in for diagnostics. The technician should review both the driveability and repair history worksheets. Refer to Technical Management Support / Vehicle Inspection Forms & Symptom Checklists.

Verify The Customer Complaint
To verify the customer complaint the technician will need to run or road test the vehicle and verify that the customer complaint is a deviation from normal operation.

Check For Applicable Technical Service Bulletins
Check all available service information. This includes PROM or manual updates, warranty, and recall information. Difficult to diagnose problems are often described in periodical publications by experienced technicians who have encountered like symptoms in similar vehicles.

Service Diagnostics (Paper and Electronic)
1. Diagnostic Trouble Code (DTC) Stored Follow the designated DTC Table exactly to make an effective repair.
2. No DTC - Select the symptom from the symptom tables and follow the diagnostic paths or suggestions to complete the repair, or refer to the applicable component/system check.
3. No Matching Symptom - Analyze the complaint. Develop a plan for diagnostics. Utilize the wiring diagrams and theory of operation.
4. Intermittents - Conditions that are not always present are intermittent. In order to resolve Intermittents, perform the following steps:

4.1. Observe the history DTCs, the DTC modes and, the freeze frame data. Call technical assistance for similar cases where repair history may be available. Combine the technician knowledge with efficient use of the available service information.
4.2. Evaluate the symptoms and conditions described by the customer.
4.3. Use a check sheet or other method in order to identify the circuit or electrical system component.
4.4. Follow the suggestions for intermittent diagnosis found in the service documentation.
4.5. The Tech 1, Tech 2 and Fluke 87 scan tools have data capturing capabilities that can assist in detection of Intermittents.

5. Vehicle operates as designed/No trouble found
6. Call technical assistance for similar cases where repair history may be available. Combine technician knowledge with efficient use of the available service information.

6.1. This condition exists when the vehicle is found to operate normally.
6.2. The condition described by the customer may be normal. Verify against another vehicle that is operating normally.
6.3. The condition may be intermittent. Verify the complaint under the conditions described by the customer before releasing the vehicle.

Re-Examine the Complaint
When the complaint cannot be successfully found or isolated, a reevaluation is necessary. The complaint should be re-verified and could be intermittent or normal.

Repair and Verification Tests
After isolating the cause, the repairs should be made. Then validate for proper operation and verify that the symptom has been corrected. This may involve road testing the vehicle in order to verify that the complaint has been resolved.

Checking The Basics
All diagnostics should begin with checking the basics.

Computers and Controls / Flow of Diagnostics
The Computers and Controls / Flow of Diagnostics is an organized approach to identifying a problem created by an electronic engine control system malfunction.