Inductive crankshaft position sensor - Cranking

The purpose of this test is to evaluate the operation of an inductive Crankshaft Position Sensor (CPS) with an earth return circuit (non-floating ground) based on the output voltage and frequency during engine cranking.

Connection Guidance

Connection for diagnostic work will of course vary dependant 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.

Dependant on difficulty of access, choose from,

1. Breakout leads.
2. Back -pining probes.

Testing Sensors and Actuators; (to include relevant circuit/connectors).

• When testing a sensor, it is desirable to gain access at the control unit.
• When testing an actuator, it is desirable to gain access at the actuator.

How to perform the test

NOTE, engine cranking not starting.

1. Connect PicoScope channel A to the vehicle.
2. Minimise the help page and with the example waveform on your screen PicoScope has already selected suitable scales for you to capture a waveform.
3. Select GO or press the space bar to see live data.
4. Crank the engine for around 3 seconds to capture your waveform.
    

Component Graphic

Example waveform

Waveform Notes

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.

 

Waveform Library

The Waveform Library has 559 examples of inductive crankshaft sensor.

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select ‘crankshaft sensor inductive’.

Further Guidance

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 modern 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.

• Engine will not start
• Engine stalls
• Problems starting
• Error code is stored

Causes of Crankshaft Sensor Failure.

• Internal sensor coil short circuits
• Open circuit in harness or connectors
• Short circuit in harness or connectors
• Mechanical damage to the encoder wheel
• Soiling caused by metal abrasion sticking to permanent magnet

 

Generic DTC’s Crankshaft Position Sensor.

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

Mechanical Checks.

If the waveform indicates a fault, make a physical inspection of the CPS. The list below highlights some key areas for inspection.

• CPS fitment to housing / mounting. The sensor must sit correctly and securely.
• Inspect CPS tip for damage / foreign object.
• Inspect pick-up ring for damage / foreign object.
• Inspect air gap between CPS and pick-up ring.
• Inspect run-out of pick-up ring.
• Inspect end float at the pick-up ring.
• Inspect CPS for water / coolant ingress and corrosion.
• Inspect CPS and ECM connector pin number alignment as per vehicle specification.
• Inspect CPS location for sources of interference (high current consumers E.g. starter motor, ignition coils and injectors).

AT017-5

Suitable accessories