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

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 The tool used in this guided test may have been superseded and the product above is our latest version used to diagnose the fault documented in this case study.

Gasoline direct injection - injector voltage and current

The purpose of this test is to check the Gasoline Direct Injection (GDI) injector control voltage and current from an Engine Control Module (ECM).



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.

To avoid possible damage to your scope, you may need to use an attenuator for this test.

Scopes with a 200 V range, such as PicoScope 4x25 models, do not need an attenuator for this test.

All other PicoScope Automotive models need an attenuator on the channel input. You can use either a 10:1 or a 20:1 attenuator provided that you adjust the PicoScope software accordingly. Select from the appropriate Channel Options menu:

  • Probe > x10 for a 10:1 attenuator
  • Probe > x20 for a 20:1 attenuator


How to perform the test

View connection guidance notes.

  1. Use the vehicle wiring diagram to identify the positive feed and switched earth circuits.
  2. Connect PicoScope Channel A to the injector positive feed circuit.
  3. Connect PicoScope Channel B to the injector switched earth circuit.
  4. Connect the low amp clamp to PicoScope Channel C.
  5. Select the 20 A scale and zero the clamp before connecting to the injector control circuit.
  6. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
  7. Start the scope to see live data.
  8. Run the engine.
  9. With your waveforms on screen stop the scope.
  10. Turn off the engine.
  11. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.


The orientation of the 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

Injector feed and switched earth voltages and circuit current during engine cranking conditions.

Injector feed and switched earth voltages and circuit current during engine idle conditions.

Injector feed and switched earth voltages and circuit current during wide open throttle engine conditions.

Injector feed and switched earth voltages and circuit current during engine overrun conditions.

Waveform notes

These known good waveforms have the following characteristics:

  • When the injector is off, the ECM supplies 4 to 5 V to both sides of the injector circuit.
  • The ECM switches on the injector by simultaneously supplying a boosted 40 V to the positive feed side Channel A, and a path to earth, 0 V, on the switched earth side Channel B.
  • At injector switch on, the circuit current, Channel C, reaches 6.25 A.
  • Once the injector valve is fully open, the boost voltage is removed from the positive feed, which briefly reduces to 0 V, whilst the switched earth voltage remains at 0 V.
  • Within 0.1 to 0.2 ms, a pulsed, square wave, voltage is established to keep the injector valve open.
  • The circuit current holds the injector open at around 2.75 A.
  • The ECM switches off the injector by simultaneously providing 4 to 5 V to both sides of the circuit.
  • There is a peak in the switched earth voltage after the injector is switched off.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select Injector voltage or Injector current.

Further guidance

A GDI injector delivers fuel directly to the air charge within a cylinder.

The GDI injector fast reaction times enable an engine management system to operate across different cylinder charge modes, for example:

  • a homogenous air charge, having the same, stoichiometric, air-fuel mixture throughout the combustion volume; or
  • a heterogeneous air charge, having a stratified air-fuel mixture with a small, fuel rich, volume within an overall, lean, combustion volume.

GDI injectors can deliver fuel with complex spray patterns and provide multiple injections per compression stroke. Furthermore, fuel can be kept from the cylinder volume until very close to the point of ignition reducing the risk of pre-ignition or knock and allowing the use of higher compression ratios, all of which leads to better thermal and fuel efficiencies.

As fuel injection coincides with the compression stroke, GDI injection pressures must be sufficient to overcome the in-cylinder pressures that occur across all engine load conditions. Therefore, GDI systems require a high pressure, up to 200 bar, fuel delivery system consisting of a common fuel rail supplied by a high-pressure fuel pump.

The ECM improves GDI injector response times by increasing the circuit voltage during the opening phase providing additional energy to move the valve rapidly. However, once the valve is fully open, only a relatively small voltage is necessary to hold it place, which the ECM maintains with a lower, pulsed, square wave voltage.

GDI injector failures may cause loss of engine performance, misfire or excessive smoking symptoms. Possible failure modes may be:  

  • mechanical inlet or outlet blockages, sticky/stuck injector valves or defective spray patterns;
  • or electrical open, short circuits or high resistances in the wiring, solenoids or ECM.

When operating out of their normal tolerances, for example, constant short runs or cold-start operation, GDI systems can cause the build-up of soot within the engine systems, which can cause a variety of secondary issues (e.g. blocked inlets, EGR valves, turbo vanes etc.). As such, regular maintenance is essential for continued operation within tolerances.

Diagnostic trouble codes

Selection of component related Diagnostic Trouble Codes (DTCs):

P0200 – Injector Circuit Malfunction

P0201 – Injector Circuit Malfunction – Cylinder 1

P0202 – Injector Circuit Malfunction – Cylinder 2

P0203 – Injector Circuit Malfunction – Cylinder 3

P0204 – Injector Circuit Malfunction – Cylinder 4

P0205 – Injector Circuit Malfunction – Cylinder 5

P0206 – Injector Circuit Malfunction – Cylinder 6

P0207 – Injector Circuit Malfunction – Cylinder 7

P0208 – Injector Circuit Malfunction – Cylinder 8

P0209 – Injector Circuit Malfunction – Cylinder 9

P0210 – Injector Circuit Malfunction – Cylinder 10

P0211 – Injector Circuit Malfunction – Cylinder 11

P0212 – Injector Circuit Malfunction – Cylinder 12

P0213 – Cold Start Injector 1 Malfunction

P0214 – Cold Start Injector 2 Malfunction

P0216 – Injection Timing Control Circuit Malfunction

P020A – Cylinder 1 Injection Timing

P020B – Cylinder 2 Injection Timing

P020C – Cylinder 3 Injection Timing

P020D – Cylinder 4 Injection Timing

P020E – Cylinder 5 Injection Timing

P020F – Cylinder 6 Injection Timing

P021A – Cylinder 7 Injection Timing

P021B – Cylinder 8 Injection Timing

P021C – Cylinder 9 Injection Timing

P021D – Cylinder 10 Injection Timing

P021E – Cylinder 11 Injection Timing

P021F – Cylinder 12 Injection Timing

P0261 – Cylinder 1 Injector Circuit Low

P0262 – Cylinder 1 Injector Circuit High

P0263 – Cylinder 1 Contribution/Balance Fault

P0264 – Cylinder 2 Injector Circuit Low

P0265 – Cylinder 2 Injector Circuit High

P0266 – Cylinder 2 Contribution/Balance Fault

P0267 – Cylinder 3 Injector Circuit Low

P0268 – Cylinder 3 Injector Circuit High

P0269 – Cylinder 3 Contribution/Balance Fault

P0270 – Cylinder 4 Injector Circuit Low

P0271 – Cylinder 4 Injector Circuit High

P0272 – Cylinder 4 Contribution/Balance Fault

P0273 – Cylinder 5 Injector Circuit Low

P0274 – Cylinder 5 Injector Circuit High

P0275 – Cylinder 5 Contribution/Balance Fault

P0276 – Cylinder 6 Injector Circuit Low

P0277 – Cylinder 6 Injector Circuit High

P0278 – Cylinder 6 Contribution/Balance Fault

P0279 – Cylinder 7 Injector Circuit Low

P0280 – Cylinder 7 Injector Circuit High

P0281 – Cylinder 7 Contribution/Balance Fault

P0282 – Cylinder 8 Injector Circuit Low

P0283 – Cylinder 8 Injector Circuit High

P0284 – Cylinder 8 Contribution/Balance Fault

P0285 – Cylinder 9 Injector Circuit Low

P0286 – Cylinder 9 Injector Circuit High

P0287 – Cylinder 9 Contribution/Balance Fault

P0288 – Cylinder 10 Injector Circuit Low

P0289 – Cylinder 10 Injector Circuit High

P0290 – Cylinder 10 Contribution/Balance Fault

P0291 – Cylinder 11 Injector Circuit Low

P0292 – Cylinder 11 Injector Circuit High

P0293 – Cylinder 11 Contribution/Balance Fault

P0294 – Cylinder 12 Injector Circuit Low

P0295 – Cylinder 12 Injector Circuit High

P0296 – Cylinder 12 Contribution/Balance Fault


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: Gasoline direct injection - injector voltage and current