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:
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.
An indirect injector in a multi-point injection system 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.
Typically, coolant and air temperature, manifold pressure, air flow and driver demands are included.
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 employ solenoid controlled valves, which work against a spring force acting to close them. As such, these injector valves will open when sufficient current flows through their circuit. If there is insufficient current, the injector valve will not open fully.
The solenoid injector circuit is connected in parallel to a constant battery feed via a relay, a dedicated control module or ECM.
The 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, the injector solenoids build and store energy, until they are saturated. When the current flow is stopped, the stored energy is returned to the circuit. This characteristic produces the large voltage spike visible in the injector waveform. The peak voltage varies from vehicle to vehicle; some injector circuits include a Zener diode or a resistor-capacitor combination that limits, or squares-off, the peak.
The hump, observed as the waveform voltage spike decays, occurs as the valve spring forces the injector valve rapidly back to its closed position. If the hump is missing, the valve may not be moving properly.
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 to 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.
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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