The purpose of this test is to evaluate the operation of an inductive crankshaft position sensor with an earth return circuit (non-floating ground) based on the output voltage and frequency 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):
NOTE, engine cranking not starting.
A good waveform, showing good voltage levels with changes in amplitude and frequency as the engine cranking speed changes.
Clear indication of the ‘missing tooth’ signal.
No significant spikes or inconsistent pattern breaks.
As stated in the purpose of this test, it is looking for a crank sensor signal whilst cranking the engine. It is assumed therefore that the engine is a ‘non-starter’ and the test is looking for a viable signal from the sensor thereby eliminating it from the diagnostic procedure.
Many engine management systems will not allow an engine to start without a clear crank sensor signal.
The signal will inform the Engine Control Module (ECM) of both the speed and position of the engine.
If the signal does not exist then the engine will not start, however, the signal must also be within the ECM parameters. Too weak or erratic a signal may be a sensor fault or a sensor positioning error. (Please see the list of mechanical faults in this article).
The example waveform in this test was taken from a high capacity high compression 4-cylinder engine and is a known good signal, the engine fuel system had been disabled in order to carry out the test. We can say in this case that the sound from the cranking engine matches the waveform frequency and amplitude variations.
On a more ‘standard’ fast cranking engine this example could be diagnosed as an erratic signal and may be outside of the ECM parameters thereby preventing starting.
Typical Crankshaft Sensor Faults.
Causes of Crankshaft Sensor Failure.
If the waveform indicates a fault, make a physical inspection of the CPS. The list below highlights some key areas for inspection.
P0016 - Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A
P0315 - Crankshaft position (CKP) system variation values are not stored in the PCM memory
P0335 - CKP Sensor A Circuit Performance
P0336 - Crankshaft Position (CKP) Sensor A Performance
P0337 - Crankshaft Position (CKP) Sensor Circuit Low Duty Cycle
P0338 - Crankshaft Position (CKP) Sensor Circuit High Duty Cycle
P0339 - Crankshaft Position (CKP) Sensor Circuit Intermittent
P0385 - Crankshaft Position (CKP) Sensor B Circuit
P0386 - Crankshaft Position (CKP) Sensor B Performance
P0387 - Crankshaft Position Sensor B Circuit Low Input
P0388 - Crankshaft Position Sensor B Circuit High Input
P0389 - Crankshaft Position Sensor B Circuit Intermittent
P1324 - Crank RPM Too Low
P1335 - CKP Circuit
P1336 - Crankshaft Position (CKP) System Variation Not Learned
P1345 - Crankshaft Position (CKP)-Camshaft Position (CMP) Correlation
P1372 - Crankshaft Position (CKP) Sensor A-B Correlation
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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October 28 2015
excellent information source