Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Ignition Coil Testing
Ignition system faults may be diagnosed with the DISplus or GT1 if equipped with a Measurements Interface Box. Enter the test plan for ignition coil (a choice of four coils, 1, 2, 3, or 4 will be given). The oscilloscope will be pre-set during the test plan.
When measuring kV on cylinders 1 and 2, remember that the voltage is flowing from the outer electrode to the center and back to the coil. This will be indicated by negative voltage readings on the oscilloscope. kV's on cylinders 1 and 2. The voltage will be approximately 20% higher than on cylinders 3 and 4.
- Secondary output in the 7- 9 kV range are normal during firing of the cylinder on the compression stroke and 3 - 5 kV for the cylinder on the wasted spark stroke.
- A defective coil will influence two cylinders, a defective plug wire only influences one cylinder.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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