San Diego Diagnostic Service-Why a diagnostic charge?

Many people believe that their car can be connected to a diagnostic machine and it will tell us what is wrong with the vehicle. This is not entirely true. In reality, we have a variety of diagnostic equipment that communicate with the computers on your vehicle.  This provides us valuable data to guide us through the diagnostic process. Unfortunately, many times the data is vague or generic. On 1996 and later vehicles, the vehicles on board computer can provide significant amounts of data, but not definitive answers. On 1995 and earlier, there is very limited data making it more labor intensive to figure out what is wrong.


A thorough diagnostic process involves a variety of procedures. Generally, the first step is to connect the diagnostic scanner to the vehicle and check for any malfunction codes. The mechanic can also look at data streaming in real time from the vehicles computer. When there is a trouble code stored it typically indicates what area or system is malfunctioning. Using this information our mechanics can put their training, experience and trouble shooting skills to work and properly identify the cause of the malfunction and recommend the best, most effective way to correct it. This is done by following diagnostic trouble shooting flow charts. These charts indicate which tests should be performed, and the results will indicate if additional tests are needed. Some of these charts are short, others are several pages. The mechanics knowledge and experience guide him where to begin in the troubleshooting process. Below are some examples of some of the procedures that would be used in the diagnostic process.


• Talk to the customer to get the most detailed information about the complaint and review records from previous repairs.
• Drive vehicle to verify complaint.
• Check databases for recalls and/or technical service bulletins, etc.
• Visual inspection of suspected areas on the vehicle.
• Wiggle tests (of electrical connections).
• Connect scanner to obtain codes and inspect real time data stream.
• Perform electrical and/or mechanical tests of suspect component including lab scope patterns.
• Research information on the problem indicated from places like Alldata, Mitchell, OEM Websites and the International Automotive Technicians Network database.
• Check condition of battery and alternator.
• Possibly perform a compression test.
• Possibly perform a leak down test.
• Possibly perform a vacuum test.
• Possibly perform a cooling system pressure test.
• Possibly perform a smoke test.
• Possibly perform fuel pressure, quantity and quality tests.
• Possibly check fuel injectors fuel spray pattern.
• Possibly perform an emission test (4 or 5 gas analyzer).
• Possibly examine the ignition patterns on a scope or scanner.
• Possibly check exhaust pressure.
• Possibly check for grounds and power to components related to the fault like relays modules, etc.
• Possibly a dynamometer test.
• Consult with other techs or tech support groups if the problem is an unusually difficult one.

Diagnosing a car is not an easy thing today. To properly repair your car, truck, SUV or hybrid a shop must be equipped with sophisticated and expensive equipment as well as subscriptions to technical information providers and most importantly very intelligent, well-educated expert mechanics!  Stop by