Injector and injector current

The purpose of this test is to monitor the injector voltage and current to determine the integrity of the injector circuit and the operation of the injector.

    To avoid damage to your scope, you may need to use an attenuator for this test. These instructions do not refer to an attenuator as it is based on our PicoScope 4425 automotive scope.

If you are using a previous PicoScope Automotive model, you will need either a 10:1 or 20:1 attenuator and will need to adjust the Probe settings for the relevant channel. These settings can be found under the Channel Options button, then:

• Probe > 10:1 Attenuator
• Probe > 20:1 Attenuator

How to perform the test

Channel A

Plug the premium test lead into Channel A on the PicoScope and place a large black clip on the test lead with the black moulding (negative), and a back-pinning or multimeter probe onto the test lead with the red moulding (positive). Place the black clip onto the battery negative terminal and probe the switched earth side of the injector with a back-pinning or multimeter probe.

Alternatively the TA012 break out lead can be used, as illustrated in Figure 1.

Channel B

Connect the current clamp into Channel B on the PicoScope*. The current clamp should be placed onto the fuel injector's supply wire.

Alternatively the TA012 break out lead can be used placing the low amps current clamp on either the blue or the yellow exposed cable section of the test lead, as illustrated in Figure 2. As there is no consistency as to which terminal carries the supply, it may be necessary to observe both waveforms and select the correct one.

With the example waveform displayed on the screen you can now hit the space bar to start looking at live readings. Snap the accelerator quickly from idle to full throttle and observe the waveform expanding under acceleration and (on some models) shutting off on over-run. The waveform is stabilised by using the falling voltage to trigger the oscilloscope.

* If you have an old style current clamp with 4-mm banana plugs instead of a BNC connector, connect it to the PicoScope using the premium test lead.

Example waveform

Waveform notes

When monitoring the injector waveform using both voltage and amperage, this allows the operator to see the 'correct' time that the injector is physically open. It can be clearly seen from the current waveform (shown in red), that the waveform is 'split' into two easily defined areas.

The first part of the waveform is responsible for the electromagnetic force lifting the pintle; in this example the time taken is approximately 1.6 ms. This is often referred to as the solenoid reaction time. The remaining 2.5 ms is the actual time the injector is fully open. This, when taken as a comparison against the injector voltage duration (blue trace), is different to the 1.8 ms shown.

When the earth is removed a voltage is induced into the injector and a spike approaching 85 volts is recorded.

Technical information

Please see individual waveform topics:

  • Multi-point injector (Voltage)
  • Multi-point injector (Current)


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

  • 30 A (low amps) current clamp


  • 20 A / 60 A DC (low amps) current clamp


  • 2 Pin AMP connector breakout lead


  • Back-pinning Probe Set


  • Flexible Back-pinning Probe


  • 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: Multi-point (Voltage vs Current)