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

  • 10:1 Attenuator

  • 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 The tools used in this guided test may have been superseded and the products above are our latest versions used to diagnose the fault documented in this case study.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 primary ignition voltage (dual) and current

The purpose of this test is to examine the primary driver voltages and the current draw from a DIS coil pack. 



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. Use manufacturer data to identify circuit functions.
  2. Ensure the ignition is turned off.
  3. With a 10:1 attenuator on PicoScope Channel A connect to one of the coil driver circuits.
  4. With a 10:1 attenuator on PicoScope Channel B connect to the second coil driver circuit.
  5. Connect the low amp clamp to PicoScope Channel C. Select the 20 A scale and zero the clamp before connecting around the coil unit power supply circuit.
  6. Start the engine and run at idle.
  7. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
  8. Start the scope to see live data.
  9. With your waveforms on screen stop the scope.
  10. Turn off the engine and ensure the ignition is off.
  11. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.


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

The waveform shows the driver voltages for both windings in the ignition coil. It also shows the current drawn during both driver events, allowing you to see if both coils are drawing the same amount of current during the operating cycle.

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 voltage

Further guidance

Distributorless Ignition System (DIS)

DIS has major advantages over the distributor-based ignition system. These advantages include an absence of rotating high-voltage distribution components, and far lower levels of electromagnetic interference.

DIS is fitted only to vehicles that have an even number of cylinders, such as 2, 4, 6 or 8. This is because two cylinders are connected to one coil, which can send a spark to both cylinders at the same time. This system is commonly known as a wasted spark system. The two spark plugs are arranged so that one is fired on the power stroke of the engine and the other on the exhaust stroke of the opposing cylinder, offset by 360 degrees. After a complete rotation of the engine the two cylinders are now on the opposing strokes and the two spark plugs fire again but with opposite roles.

On a four-cylinder engine, there are two coils with individual drivers that tend to operate cylinders 1 and 4, and 2 and 3. This means there is a dual spark every 180 degrees, with one of those sparks wasted on an exhaust stroke of the opposing cylinder which is firing on the power stroke.


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 (Dual) vs Current