Multi-point injector - voltage and 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.

Connection guidance

Connection for diagnostic work will vary dependent on application.

Technicians should wherever 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 module.
  • When testing an actuator, it is desirable to gain access at the actuator.
   

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 Channel Options, then:
• Probe > 10:1 Attenuator
• Probe > 20:1 Attenuator

How to perform the test

  1. Connect a breakout lead between the injector and loom connectors.
  2. Connect PicoScope Channel A to the injector power supply at the breakout lead.
  3. Connect the low amp current clamp into Channel B on your PicoScope. Switch on the current clamp and select the 20 A scale. Zero the current clamp before connecting to the vehicle.
  4. Attach the current clamp onto the breakout lead, injector supply circuit.
  5. Minimise the help page and with the example waveform on your screen PicoScope has already selected suitable scales for you to capture a waveform.
  6. Run the engine.
  7. Select go or press the space bar to see live data.
  8. Turn off the engine.
  9. Use the Waveform Buffer and Zoom tools to examine your waveform.

Waveform notes

These known good waveforms have the following characteristics:

Initially, the waveform shows voltage on the switched earth side of the injector at battery voltage, 14-15 V, no current is flowing and the injector is off.

When the Engine Control Module (ECM) provides an earth path the trace switches to 0 V and current begins to flow. At this point the injector valve starts to open, marking the start of injection.

The current increases in two phases. The change point, at around 1.5 ms, marks when the injector valve is fully open.

Around 3-4 ms after the start of injection, the circuit current reaches its peak value, which is sustained for the remainder of the injection period.

Both the injector voltage and current show that the injection duration is about 4.25 ms.

When the injector is switched off at 4.25 ms and the current flow stops, there is a spike in the waveform voltage, which peaks at about 85 V, and the injector begins to close.

At about 1 ms after injector switch off, there is a hump in the decaying voltage spike.

The waveform voltage remains at battery positive volts until the next start of injection.

Waveform Library

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

Example multi-point petrol injector

Example cross-section multi-point petrol injector

Further guidance

An indirect injector is used to deliver the correct quantity of atomised fuel to the air in the inlet tract, as it is drawn through to a cylinder.

A multi-point injection system has one injector per cylinder supplied by a common fuel rail. As the rail pressure regulator maintains a constant pressure difference between the injectors’ fuel inlet and outlet to the manifold, the injected fuel quantity depends only on injection duration.

The ECM uses input signals from a range of sensors dependent on both system type and manufacturer application in order to calculate injection duration.

For example, when a cold engine is started the ECM increases the injection duration to counter the effects of cold starting, but then decreases the injection duration as the engine reaches its normal operating temperature.

Indirect-injection fuel injectors employ solenoid-controlled valves, which work against a spring force acting to close them. The valves open when sufficient current flows through their circuit. The injector valve will not open fully if there is insufficient current.

An ECM, or dedicated control module, dictates the current flow in each injector circuit by switching in and out the individual injector earth paths.

When current flows, an injector solenoid builds and stores energy, until it is saturated. When the current flow stops, the stored energy is returned to the circuit, inducing a large voltage spike. The voltage spike varies from vehicle to vehicle; some injector circuits include a Zener diode or a resistor-capacitor combination that limits, or squares off, its peak.

The decay of the voltage spike is sometimes momentarily interrupted by the action of the valve as its spring forces it rapidly back to its closed position. This indicates normal movement of the injector valve.

Example sequential circuit

Example simultaneous bank circuit

There are two types of multi-point injection system:

Sequential systems fire injection pulses each 720° of crankshaft rotation to coincide with the opening of each cylinder inlet valve. Injection durations range from 4-5 ms at engine idle.

Simultaneous systems fire all the injectors together in an inline engine arrangement, or each bank of injectors in a ’V’ arrangement, twice every 720° of crankshaft rotation. In these systems, less fuel is injected per injection, therefore their injection durations are reduced to around 2.5 ms at engine idle.

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

GT388-2

Disclaimer
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

  • Premium 6-way breakout lead set

    £269.00

  • 30 A (low amps) current clamp

    £259.00

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

    £111.00

  • Back-pinning Probe Set

    £40.00

  • Flexible Back-pinning Probe

    £3.00

  • PicoScope Battery Clip

    £2.75

  • Premium Test Lead: BNC to 4 mm, 3 m

    £47.00

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Guided test: Multi-point injector - voltage and current