Products suited to this guided test*
  • 20 A / 60 A DC (low amps) current clamp

  • Multimeter Probes

  • *At Pico we are always looking to improve our products. The tools used in this guided test may have been superseded and the products above are our latest versions used to diagnose the fault documented in this case study.

Distributorless Ignition System primary ignition voltage and current

The purpose of this test is to examine primary ignition voltage and current within a DIS unit.



This test involves measuring a potentially hazardous voltage.

Please ensure you follow manufacturers' safety instructions and working practices and ensure the rated voltage for all accessories you are using meets or exceeds the expected voltage.


How to perform the test

View connection guidance notes.

  1. Ensure the ignition is turned off.
  2. Connect the 10:1 attenuator to PicoScope channel A.
  3. Connect PicoScope channel A to the ignition coil negative terminal and to earth.
  4. Connect the low amp current clamp to PicoScope channel B.
  5. Select the 20 A scale and zero the clamp.
  6. Connect the clamp around the coil power supply circuit.
  7. Start the engine and run at idle.
  8. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
  9. Start the scope to see live data.
  10. With your waveforms on screen stop the scope.
  11. Turn off the engine and ensure the ignition is off.
  12. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.


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


The orientation of the current clamp relative to the wire will determine whether it has a positive or negative output. If a live waveform does not appear on your screen, or appears to be inverted, try reversing the orientation of the clamp.

Example waveform

Waveform notes

These known good waveform(s) have the following characteristics:

Channel A is a typical primary ignition trace illustrating dwell, firing voltage and spark duration.

Channel B illustrates the current build up in the primary coil throughout the dwell duration.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select, DIS / wasted spark ignition primary current, or voltage

Further guidance


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.

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Guided test: Primary Voltage (Single) vs Current