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Streamlining the Diagnostic Process


Streamlining the Diagnostic Process

Diagnostic Process StepsThere has been an “explosion” of new systems to help vehicles become safer in the last few years.  Adaptive cruise control and parking assist sensors used to be the “cool new feature” in the 1990s.  Then In 2007, Blind spot monitoring.  Then newer technologies such as infrared night vision, radar collision avoidance systems, and sophisticated cameras created a new group of systems called “ADAS” – Advanced Driver Assistance Systems.  The increase in sensors and ECU’s built the foundation for the next generation vehicles coming. All these new sensors make vehicle diagnosis and repair more complicated than ever.

In 2018 FCA vehicles began using a Secure Gateway Module.  This Secure Gateway Module (or SGW) is located under the dashboard and acts like a hardware firewall between the vehicle’s network and the outside world.  The module will allow “Read Access” (read codes, read data), but will restrict any functions that send a command to the vehicle, such as clearing codes or functional tests.  Only authorized tools are allowed access to these functions.  All Snap-on tools support FCA as well as other existing OEM secure linkages with current software. 

But there is some good news, too. The same computer and information technologies that add complexity to vehicles, are enabling improved diagnostic strategies that drastically simplify and reduce time spent in diagnosis and repair.

The question is do you have a diagnostics process? Most technicians have their own specific approach for diagnosing typical drivability problems, electrical or mechanical issues. Why is it that one technician can take 20 minutes diagnosing a car and another may take a week to only come up with the same fix?

The first tech focused on the customer complaint and the effect it had on the vehicle in order to identify the cause.  The other technician is implementing a shotgun approach to find the fix.  Although this approach can lead to the fix, it is not the most productive method. Flying by the seat of your pants doesn’t work in today’s sensor and ECU environment.

There’s a step process that simplifies the fix path. Certainly there could be more but we’ll start with the simplest approach.

Step 1. Verify the Customer’s Complaint

Ask questions. Document the Condition! Is complaint present now? When does it happen? Cold?  Warm-up? Hot? Under what Conditions? Driving Fast or Slow? Idle or under load? Can you match the condition?

Step 2: Scan Checks

A pre-scan shows all supported modules, not just engine in that vehicle. Many systems today are interlinked.  Some systems do not turn on a light or put a message on the vehicle’s Diagnostic Information Center. Uncover unseen issues or find hidden safety issues. Think of how this helps your repair customer. 

General Repair

General Repair Shops that perform a pre-scan makes it easier to charge for diagnostics. Furthermore, shops can use the report to validate if a vehicle is worth fixing and advise the customer accordingly – providing them an easy to understand handout helping them to feel more confident that the vehicle has been properly checked over and of the suggested repair.


Every shop is in the emissions business. Three critical monitors must be set to 'Complete' status for cars to pass an emissions test required in states, counties or provinces. OBDII is designed to be a 'rolling emissions test', so use the report to communicate probles by setting the readiness monitor status to 'Complete' to flag a detected problem.

Also, with current software a Snap-on tool will upload your pre- and post-scan report automatically to the Snap-on Cloud within seconds. It can be shared via a link, SMS Email or PDF from any PC or phone anywhere in the world from your free account.

Step 3: Technical Service Bulletins (TSBs).

If TSBs match a code or symptoms follow the OEM recommendation for additional testing or repair. Manufacturers are repairing cars with software and firmware. Many technicians spend way too much time trying to find a problem that the manufacturer has already discovered. Snap-on offers TSB availability in as little as 2 weeks but never more than 8 weeks after release from a manufacturer in our ShopKey® Pro product. Technical service bulletins should be checked early in your diagnostic procedure and never overlooked.

Step 4: Functional Tests and Guided Component tests.

Functional Tests

Functional Tests can pinpoint a problem or verify the repair. These tests command a window to go up or down, turn signals to work and more. This literally could cut your diagnostic time in half.

And then there is service resets and relearns… repairs have components that need to be reset or relearned after a simple repair. For instance, a 2006 General Motors car – replacing the oxygen sensor sounds easy enough, but if you do not reset the Resistance Calculated Oxygen Temperature Circuit back to factory level you risk damaging the sensor prematurely. This just one of thousands of examples needed to be done today.  

Guided Component Tests

Guided Component Tests provide an extensive collection of vehicle specific component tests and reference information for engine, transmission, ABS, charging, transfer case, suspension, ADAS systems and more

Use a tool that provides vehicle specific preconfigured meter tests and reference information designed to help save diagnostic time, plus verify faulty components and the repair. Guided instructions and reference information should be included, such as component locating, appropriate test selecting, showing test lead connections and electrical connector and pin configurations. Also, test results (including waveform examples), procedures, tips, and specifications.

Step 5: Post Scan.
Customers expect and demand their vehicle works exactly as the manufacturer intended. All post-scan reports are date and time stamped, and easy to understand. These complete “health” checks provide customers the confidence that the repair has corrected the problem.

New vehicle systems will only accelerate. And, diagnostic tools need to ‘go big or go home’ to support your needs with faster and easier repair frameworks through process and technology.

But, no matter the tool you use, your diagnostic process is key. Spend time looking at thought-out steps versus a shotgun approach. See what you can do today to reduce wasted time and improve throughput to your advantage.