Diagnostic Scan

Using a Diagnostic Scanner on your vehicle.

How does it work and why is it important?

It is important to know that a diagnostic scan allows us to access your vehicle’s fault codes but does not tell us how to fix them.


Why am I being charged for a diagnostic scan?

Diagnostic equipment is expensive as it requires a license fee and Qualified Technicians who studied diagnostics to diagnose the faults.

  • Licenses – besides the original cost price to purchase the machine, a license also needs to be renewed each year
  • Technician training – each technician that uses a diagnostic machine must be qualified to do so. The technician will learn how to understand each fault code and use that knowledge to trace ‘Why’ the fault has come up
How does my car read faults?

All newer cars have sensors that sit around the Engine, Transmission, Exhaust, Brakes and Cooling System. These sensors constantly read the information that flows past them. This information could be anything from the air/fuel ratios in your exhaust to the temperature of your engine.

If one of the sensors pick up a fault it will send a signal through to the ECU (Engine Control Unit), the ECU will then store this fault. If the fault that comes through is something the ECU finds dangerous to your car, or you, it will send a signal and a light will come up on your dashboard.

How does the diagnostic scanner work?

Once plugged in, the diagnostic machine scans your vehicle’s ECU and bring up all the stored faults. The fault code, however, can only tell the technician which location the fault is coming from, or from which sensor. It however does not tell the technician ‘Why’ it is showing that specific fault or how to fix it.

Additional costs may be needed, depending on the type of fault code. The technician might need to strip or even conduct further tests to determine which part is faulty.


  • Car comes into the workshop with an engine light on the dash. We then quote the customer on a diagnostic scan.
  • The diagnostic scan shows us that there is a problem with the oil pressure in the engine being too low.
  • We will then first quote the customer to clean the oil pressure switch. This is the least expensive option and will most likely solve the issue. Unfortunately, the fault returned after a couple of days.
  • For the next step, we send the customer a quote to remove the sump. Once the customer has agreed to the quote we proceed with stripping.
  • The sump was then removed and we saw that the oil pick up was blocked by timing belt fibers. Therefore, causing the oil pressure to drop and read as low.
  • The second last step would be to quote the customer on cleaning the oil pick-up and replacing the car’s timing belt.
  • Once the quoted repair is complete, the fault is then cleared from the ECU, and it did not return

In this example, we could have easily just replaced the oil pressure switch, but this would not have resolved the problem. In order to resolve the issue, we needed to complete additional stripping and testing after the diagnostic scan. We recommend that a qualified technician, from a reputable company such as autoworks scans your vehicle. This is to ensure that you do not pay for any unnecessary repairs that do not solve the issue.

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