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EFI Diagnosis. Step 1 – Listen to the Customers Complaint. The customers complaint will point you in the general direction in your diagnosis Don’t allow the customer to steer you in the wrong direction
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Step 1 – Listen to the Customers Complaint • The customers complaint will point you in the general direction in your diagnosis • Don’t allow the customer to steer you in the wrong direction • Get used to the customer’s language (Does it sound like a rod knocking, or sound like when the kids put wooden blocks in the cloths dryer?) • Don’t tell the customer that their “diagnosis” is wrong (at least not directly) • Ask relevant questions (Engine temperature, Speed, Frequency) • Don’t jump to conclusions
Step 2 – Verify the Complaint • Test drive the vehicle and verify the complaint • Helps you more clearly understand the customer’s complaint • You will then know what to look for after making the repair, to verify that the symptoms are gone • Make note of relevant conditions (engine load, RPM, throttle position, engine temp, transmission gear)
If You Can’t Duplicate the Complaint • Have the customer drive the car • It may be that the customers driving style is contributing to the complaint • Ask the customer for more details about the complaint • Check TSB’s (Technical Service Bulletins) • Check the ECM for any stored fault codes
Once You Have Verified the Complaint • Systematically narrow your diagnosis down • Troubleshooting chart • Use service information • Sensor range specifications • Wiring diagrams • Description of operation
Once You Have Found the Problem • Talk to the customer and explain to them, in as non-technical terms as possible, what you have found. Address the following questions before the customer asks: • What is the problem? • What caused the problem? • What should be done to repair the problem? • What will it affect if the problem isn’t repaired?
Once the Problem Has Been Repaired • Test drive the vehicle to verify that the repair has indeed fixed the problem • There may be additional problems • When test driving, notice any other problems with the vehicle, even if they aren’t related to the original problem the customer came in for • Let the customer know about any problems you noticed when test driving and let them know how important it is to have them repaired • What is the problem? • What caused the problem? • What should be done to repair the problem? • What will it affect if the problem isn’t repaired? • Clear any trouble codes stored in the ECM
Diagnosis Equipment • Your Brain • Service Manual • Scan Tool • DVOM • Lab Scope • Fuel Pressure Gauge • 4 or 5 Gas Analyzer • Compression Tester • Leakdown Tester
Scan Tool Diagnosis • A scan tool is a useful piece of diagnostic equipment and will allow us to “see what the computer is seeing” • A scan tool is not magic and will not fix the vehicle by itself • Scan tool will provide us with various information • Trouble Codes • Data Stream • Service Programming (OBDII with a Tech II or equivalent)
Trouble Codes • Trouble codes will be set if the ECM sees sensor data outside a specific range • Look at the service information for specifics • You must determine why that sensor was out of range • Faulty sensor • Sensor was monitoring improper engine operation • I.E. O2 Lean Code • Faulty O2? • Clogged Fuel Filter?
Data Stream • Using a scan tool to monitor the data stream, essentially allows you to see what the ECM is seeing, in terms of the various sensor signals • By referencing the service information, we can determine if the value the ECM is seeing is correct