Coil-on-plug ignition - secondary vs primary

You will require a PicoScope to perform this test. A list of suitable accessories can be found at the bottom of this page.

Note: This helpfile refers to a 20:1 attenuator. If you are using a 10:1 attenuator please adjust the Probe settings for the relevant channel. These settings can be found under the Channel Options button, then: Probe > 10:1 Attenuator.

How to perform the test

Channel A: Primary ignition voltage

Plug the 20:1 Attenuator into Channel A on the PicoScope and plug a BNC test lead into the attenuator. Fit a large black clip on the black test connector (earth) and connect the clip to the battery negative terminal. Unplug the coil-on-plug unit's connector and join the two halves using a Universal Breakout Lead of the appropriate size, as illustrated in Figure 1. Identify the wire in the breakout lead that carries the coil-on-plug primary connection, and plug it into the coloured connector on the BNC test lead.

Channel B: COP probe

Using the COP Probe cable with ground clip (TA033), connect the end with the ground clip to the scope's Channel B input and the other end to the COP Probe. Connect the ground clip to a reliable ground point on the engine block.

When placing the tip of the probe on the coil, ensure that you use the flat edge. Try to be consistent with the position on the coil: find the best signal on the first coil to be tested and then repeat that on the other coils.

Example waveform

Waveform notes

The waveforms that you will see during this test are discussed in these topics:

  • Channel A: Primary ignition waveform
  • Channel B: Secondary COP ignition waveform


This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.

Suitable accessories

  • Connector breakout lead kit A


  • 10:1 Attenuator


  • PicoScope Battery Clip


  • Large Dolphin/Gator Clips


  • Premium Test Lead: BNC to 4 mm, 3 m


  • Premium Test Leads: Set of four leads 3 m (TA125 - TA128)


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Guided test: Secondary vs Primary