Bosch CDI3 injector - current

The purpose of this test is to evaluate the correct operation of the Bosch Cdi 3 diesel solenoid injector based on current flow, response, and formation during engine run conditions.

Connection guidance

Connection for diagnostic work will vary dependent on application.

Technicians should whenever possible gain access to the test circuit without damage to seals and insulation. If this is not possible then make sure appropriate repairs are completed.

General connection advice

PicoScope offers a range of options within the test kits.

Dependent on difficulty of access, choose from:

  1. Breakout leads.
  2. Back-pinning probes.

Testing sensors and actuators (to include relevant circuit/connectors):

  • When testing a sensor, it is desirable to gain access at the control unit.
  • When testing an actuator, it is desirable to gain access at the actuator.

How to perform the test

Connect the current clamp to Channel A of the PicoScope. Select the 20 A range if required and switch the current clamp on. Press the zero button before connecting the clamp to the circuit.

Attach the low current amps clamp to the signal wire from the Common-rail Diesel Injection (CDi) control unit to the injector as shown in Figure 1.

Example waveform

Waveform notes

The waveform in the illustration shows pilot and main stages of injection. The traces will vary depending on engine load and speed.

Further guidance

The common rail diesel injection system is almost a standard feature of the new diesel motor vehicle. The injector is mechanically similar to the direct injection type of injector which has been used for many years, but we no longer rely on fuel pressure to "crack off" the injector, and instead we electronically control the opening time and duration of the injector similar to a petrol injector.

The CDi version 3 system injector differs from the earlier topic within these help pages in the following ways:

  • Seven hole injector
  • 1600 bar pressure
  • A more powerful electromagnet resulting in more rapid firing of the injector and lower current consumption

Should you suspect a fault with the signal, test the wiring from the CDI control unit to the injector.

Ensure that the CDI control unit has good power supplies and grounds where required by checking with the appropriate technical data.


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


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Guided test: Bosch CDI3 injector - current