The purpose of this test is to evaluate the operation of an inductive Crankshaft Position (CKP) sensor, with no reference voltage, during engine cranking.
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:
Testing sensors and actuators (to include relevant circuit/connectors):
These known good waveforms have the following characteristics:
Channel B mirrors channel A
There is no excessive noise, nor any inconsistent breaks in either waveform.
With the engine off, prior to cranking, the voltage is constant.
At the start of cranking, there is an almost immediate response to crankshaft rotation.
As engine speed increases, amplitude and frequency increase until normal cranking speed is reached.
The waveform shows a cyclic variation in engine speed indicating the effect of the 4-stroke engine cycle: compression strokes decrease the engine speed, whereas expansion strokes increase the engine speed.
The oscillations are punctuated by a periodic gap caused by the timing reference mark, which indicates a fixed position within crankshaft rotation.
Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select ‘Crankshaft sensor (inductive)’.
A Crankshaft Position (CKP) sensor provides an Engine Control Module (ECM) with its primary engine timing reference signal. The ECM uses it to calculate the engine speed and position for accurate injection and ignition control. The signal is also used to detect engine speed anomalies from misfires etc.
An inductive CKP sensor consists of a circuit with a wire coiled around a magnet. The sensor is accompanied by a pulse wheel, typically arranged about the flywheel circumference. The pulse wheel passes through and disturbs the sensor magnetic field inducing a circuit voltage. The induced voltage depends on engine speed: the faster the pulse wheel rotates, the greater the magnetic field disturbance.
When either the tooth or gap centres align with the sensor, there is an equal and opposite magnetic field disturbance and no voltage is induced. Conversely, as either a tooth leading or trailing edge aligns with the sensor, the magnetic field disturbance and induced voltage are greatest.
Positive voltage is produced when a tooth leading edge is closer than its trailing edge, and a negative voltage is produced in the opposite case.
The missing tooth on the pulse wheel provides the main timing reference mark. As the gap passes through the magnetic field, there is a period of reduced disturbance and voltage. Furthermore, the trailing and leading edge of the teeth that immediately precede and follow the gap are further apart, thus they produce a larger net magnetic field disturbance and induced voltage.
The CKP sensor signal is critical to ECM operation and it will not start or run an engine if the signal is missing or faulty. Therefore, the sensor can cause engine cranking but not starting or engine cutting out symptoms.
Possible faults are:
Short or open circuits and high resistance in the sensor coil or circuit.
Reduced sensor output due to excessive dirt and detritus on the sensor housing or pulse wheel.
Incorrect fitment or operation of the sensor or crankshaft components, causing:
A two pin CKP sensor and ECM circuit can be arranged in two ways, with either:
Selection of component-related Diagnostic Trouble Codes (DTCs):
P0016 Crankshaft Position - Camshaft Position Correlation Bank 1 Sensor A
P0017 Crankshaft Position - Camshaft Position Correlation Bank 1 Sensor B
P0018 Crankshaft Position - Camshaft Position Correlation Bank 2 Sensor A
P0019 Crankshaft Position - Camshaft Position Correlation Bank 2 Sensor B
P0315 Crankshaft Position - system variation values are not stored in the PCM memory
P0335 Crankshaft Position Sensor A Circuit Malfunction
P0336 Crankshaft Position Sensor A Circuit Range/Performance
P0337 Crankshaft Position Sensor A Circuit Low Input
P0338 Crankshaft Position Sensor A Circuit High Input
P0339 Crankshaft Position Sensor A Circuit Intermittent
P0385 Crankshaft Position Sensor B Circuit Malfunction
P0386 Crankshaft Position Sensor B Circuit Range/Performance
P0387 Crankshaft Position Sensor B Circuit Low Input
P0388 Crankshaft Position Sensor B Circuit High Input
P0389 Crankshaft Position Sensor B Circuit Intermittent
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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