Car Diagnostic Help - Getting Straight Answers About Your Car

Car Diagnostic Help

Your Car Diagnostic Guide

A proper car diagnostic test is the first (crucial!) step towards working out a solution.  Without properly working out what's wrong you can waste a lot of time and money chasing down possible causes without actually solving the root cause.

It's better to test & not guess

Don’t allow an untrained workshop play 'swap-a-tronics' with your car. This will cost you more in the end or not get the fault repaired correctly.

Car Diagnostic Cheat Sheet

Ask these 3 Questions to work out if your mechanic has the right equipment to diagnose your car.

Benefits of Getting it Right:


Fast Results

Problems are identified FAST - no waiting around while endless tests are done.


Save Money

Save money on repairs by fixing faults before they spiral out of control and cause damage to other areas.


Lower fuel costs

Your car's emissions and electric systems are tested to ensure you aren't wasting money on unburned fuel.

When should you invest in a car diagnostic test?  Does your car have any of the following symptoms?

  • You have a problem with your car and it's not performing as it should be
  • Check engine light is on, blinking or coming on intermittently
  • Other lights like your battery light are on
  • Car is underperforming and have gone into 'limp home' mode
  • Your car is using a lot of fuel, you may see black smoke from the exhaust or notice a burnt fuel smell
  • Your car is running rough or jerking

These are just a few faults that warrant a car diagnostic test being done.  If you answered yes, to any of the above then:

  1. Book your car into a workshop that has the correct equipment. Use this cheatsheet so you know what questions to ask
  2. Complete a diagnosis sheet - the more information you can provide the better
Auto Edge’s new diagnostic machine is THE key to your vehicle’s longevity and efficiency. Get your car, van or truck a complete health check today.

The reason that diagnostics have become more important is that most vehicles now have computers that control the function of the operations from increasing fuel supply to allowing the air conditioning to operate. These computers operate within a preferred scale and if it goes out of range then problems will result.  

Problems don't always trigger an alert...

The check engine light will come on and alert you that there is fault with your car only if its safety related or to do with fuel emissions.  But there are codes that won't be apparent to the driver but will show up next time your car is scanned. 

Correct servicing of your vehicle will catch these faults before they become an issue if your servicing centre has the right equipment and is actually doing the test as part of their service.

Sometimes these checks are done and a fault may occur with an electronic component.  You may need to have your vehicle examined and a number diagnostic tests will be needed to pinpoint the defective part.

Testing Equipment - What to Look For in a Workshop

  • infrared camera

Coil Tester

This is a great tool to find ignition coils that are breaking down under load.  The tester simply loads the coil up and you can see a strong steady spark that is faultless. If it misses a beat then it should be replaced.

A Practical Example - Engine Misfire Diagnostic Process

To better explain how all this works, here is an example of how Auto Edge would deal with an engine misfire.  The car owner reported that the car was running rough, the vehicle was vibrating and had black smoke coming out of the exhaust, so this is what we did:

  • Collect Information - check diagnostic form, date of last service and information from car owner
  • Check car - how does car look, sound, feel and smell?
  • Test drive if possible
  • Scan for faults using the correct scanner
  • Research codes if any have come up on the scan
  • Test battery and charging system
  • Conduct emission test with a 5 gas analyser (this measures things like air/fuel ratio and the percentage of hydrocarbons)
  • Test spark plugs, leads and coils electronically with a KV (kilovolt tester) at idle and load
  • If coil was poor then remove it from the vehicle and load test it on bench tester
  • Replace coil and recheck, exhaust emission and test drive
  • Depending on readings obtained from KV test, all coils and spark plugs may need to be replaced as a preventative maintenance measure
  • Car is then retested to ensure all faults have been eliminated and a final test drive to confirm results.