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 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:
Testing sensors and actuators (to include relevant circuit/connectors):
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:
Initially, the waveform voltage on the switched-earth side of the injector is at battery positive voltage (around 13-15 volts) and no current flows around the injector circuit.
When the engine control module (ECM) provides an earth path to the battery negative voltage (0 volts), the injector valve starts to open and current begins to flow. This marks the start of injection.
The circuit current ramps-up in two phases, with the change between the two occurring about 1.25ms after the start of injection. The change point marks when the injector valve is open fully.
Both the injector voltage and current show that the injection duration is about 4.25ms. Within this time, at around 2.5ms after the start of injection, the circuit current reaches its peak value, which is sustained by the ECM for the remainder of the injection period.
When the ECM removes the earth path to the injector circuit (at 4.25ms), the current flow stops and the injector valve starts to close. At this point, there is a peak (spike) in the waveform voltage reaching up to around 80 volts.
Within one milli-second of the injector being switched off and as the waveform voltage decays from its peak, there is a slow-down in the decay rate followed by a rapid resumption of the initial decay rate: this ‘hump’ in the waveform voltage indicates the normal closing behaviour of the injector valve.
The waveform voltage remains at battery positive volts until the next start of injection (switch to earth).
The function of an (indirect) injector in a multi-point injection system is to deliver the correct quantity of atomised fuel to the air in the inlet tract, as it is drawn through to a cylinder.
On these systems, there is one injector per cylinder, but all injectors are supplied by a shared (common) fuel rail. As the fuel rail pressure regulator maintains a constant pressure differential between an injector’s fuel inlet and its outlet to the manifold, the ECM only needs to adjust the injection duration to control the delivered fuel quantity.
Typically, the ECM uses input signals from the coolant and intake-air temperature sensors, a manifold air pressure (MAP) sensor and/or air-flow meter (AFM) sensor, and the accelerator and throttle position sensors, etc. to calculate the required fuel quantity. 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 commonly have solenoid-controlled valves, which work against a spring force acting to close them. As such, the solenoid must be energised with a current flowing through it for the valve to open. If the solenoid is not sufficiently energised the valve will not open fully.
Typically, an injector circuit has a constant battery feed (which may be shared with the other injectors), supplied from a relay or control module, and a switched-earth (to battery negative), controlled by the ECM (or separate injection control module).
When current flows through them, solenoids build and store energy in their electromagnetic field. When the current flow stops, the solenoid's electromagnetic field collapses, producing a large but brief electromagnetic force in the direction opposite to the original current flow (i.e. a back-emf). The back-emf is visible as a large voltage spike in an injector’s switched-earth voltage waveform.
The peak back-emf voltage will vary from vehicle to vehicle; some injector circuits include a Zener diode or a resistor-capacitor combination that acts to limit the peak back-emf voltage (for example, it might be 'squared-off').
The ‘hump’ observed in an injector’s back-emf spike occurs because the valve spring forces the injector valve to move rapidly back to its closed position, which disturbs the solenoid's collapsing electromagnetic field. This waveform feature is an important diagnostic aid: if it is missing, it can be assumed that the valve is not moving properly.
There are two types of multi-point injection systems:
Sequential systems fire one injection pulse per engine cycle (720° of crankshaft rotation) in time to coincide with the opening of the inlet valve.
Simultaneous systems fire all the injectors within one bank at the same time (i.e. all the injectors in an inline engine arrangement, or each bank of injectors in a ’V’ arrangement), twice per engine cycle. In these systems, less fuel is required per injection, therefore the injection durations are reduced in comparison to sequentially firing systems (e.g. to about 2.5ms).
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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