Does a pocket sized plug in device for your vehicle, like FIXD or HUM diagnose your car?

April 16, 2020

Great Information, But Not Diagnosis

The FIXD device is being touted as one of the top 10 gifts for Christmas and that is can save you $1,000’s in unnecessary car repairs.  This device along with the HUM device are great little informational tools that can give you the code(s) that your computer sees when you are having performance issues, or if one of your warning lights has illuminated on your dash, like the check engine light.

These codes are not a diagnosis, it is a direction or starting point to work towards a diagnosis.  To diagnose a vehicle properly you have to run tests, much like a doctor does when trying to diagnose a health problem.  The following steps need to be followed:

  • Identify & duplicate the problem.
  • Scan for diagnostic trouble codes and record with all data that is in the freeze-frame. This identifies the driving conditions for when the code is being set.
  • Perform pinpoint testing of all components in the system of concern.
  • Testing modules, wiring, power, and grounds in the system of concern.
  • Analyze the testing results against the data from the engine’s computer.
  • Test theory based on results to determine the actual cause.
  • Make recommendations for repair.
  • After repair retest the system(s) to verify full functionality.

Providing Information is Different than Testing

The FIXD and HUM device does not run any tests except to give you the code, a simple explanation of the code and the most likely repair.  While this information is great to have and helps you to discern perhaps with research how urgent it is to have the vehicle diagnosed and repaired, it is not a true and accurate diagnosis.  Guessing at a repair and replacing the most probable part failure, without proper testing will cost a lot more than a proper diagnosis and repair.

For example you could have an exhaust leak and it can cause a lean condition diagnostic trouble code, or it can cause oxygen sensor codes because they are accurately reporting a lean condition due to the exhaust leak. Once the exhaust leak is fixed it could take care of all of the above-mentioned conditions.  But this device would most likely recommend replacing your oxygen sensors, and some of the newer cars have as many as 8 oxygen sensors.

You Still Need a Proper Diagnosis

A properly maintained and when there is a problem a properly diagnosed car will always be more economical than guessing.  Happy Motoring!

Karen Johnston, AUTO REPAIR INSIDER

All About Automotive, 139 NW 2nd Street, Gresham, OR 97030

Steve and Karen Johnston are owners of All About Automotive, providing auto repair and auto maintenance in Historic Downtown Gresham. If you have questions or comments, call them at 503-465-2926 or email them at cars@allaboutautomotive.com.