Camshaft position sensor - Hall effect

The purpose of this test is to evaluate the correct operation of a Hall Effect Camshaft position (CMP) sensor based on the signal voltage and formation with the engine at idle speed.

Connection guidance

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

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

Testing sensors and actuators (to include relevant circuit/connectors):

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

How to perform the test

  1. Using manufacturer data identify the signal circuit for the camshaft sensor.
  2. Connect to Channel A of your PicoScope.
  3. Start the engine and allow it to idle.
  4. Minimise the help page and with the example waveform on your screen PicoScope has already selected suitable scales for you to capture a waveform.
  5. Select GO or press the space bar to see live data.

Example waveforms

All values included in the Example waveform are typical and not specific to all vehicle types.

Channel A. Example waveform indicates the voltage signal (square waveform) output of the CMP with the engine running at idle speed.

NB. The output signal from the Hall Effect CMP can be either 5 V or 12 V depending on manufacturer.

Waveform notes

Typical values

Engine at idle speed (650-850 rpm)

  1. Signal ruler at zero volts indicating the ground level of the CMP output signal.
  2. Indicates the peak voltage  from the CMP sensor (5 V in the example above)
  3. Time Rulers: The Time Ruler handle is located at the bottom left hand corner of the waveform. Drag both Time Rulers to align with specific areas of interest within the waveform. The frequency of the signal between the Time Rulers is recorded in the Frequency Legend (5)
  4. Example waveform 1. Time Rulers highlighting one revolution of the camshaft which will rotate at half engine speed. The Frequency Legend (5) will indicate approximately half engine speed when the Time Rulers are positioned such as to indicate one complete camshaft revolution.
    Example waveform 2. (50 ms/div) Timer Rulers highlighting two camshaft revolutions. Given the camshaft is rotating at half engine speed, in order to establish the repeated pattern obtained from the camshaft pick up (and so qualify one camshaft revolution) the time base has been increased. Here we can identify the unique signal for the camshaft under test as each manufacturer will utilize various pick-ups generating different waveform patterns. What we can be assured of is the pattern will be repeated for every camshaft revolution, hence simplifying identification of a single camshaft revolution
  5. The Frequency /RPM legend indicates the frequency of the camshaft signal based upon the position of the time rulers (3). With the Time rulers placed such as to identify one camshaft revolution, PicoScope will calculate the frequency of 1 full camshaft cycle and display this value in the Frequency Legend (5) In addition, the rpm of the camshaft will also be displayed which equates to half engine speed.
  6. The Ruler Legend recording the numerical time and voltage values relative to the position of the Signal (1) and Time Rulers (3)

Waveform Library

The Waveform Library has 1154 examples of hall effect camshaft sensors.

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select Camshaft sensor (Hall effect).

Further guidance

The CMP must be considered an essential component of the modern day engine management system. While compact in construction, the correct operation of the CMP is paramount to an efficient running engine. To fully appreciate the role played by the Hall Effect CMP we must understand the operational principle behind the square wave voltage signal generated by such a critical component. Once we understand how this component functions, we can evaluate the cause of any errors within our waveform.

The Hall Effect principle relies upon a tiny voltage that is generated perpendicular to current flow through a conductor (Hall Element) in close proximity to a magnetic field. If either the current flow or magnetic field changes, the tiny voltage generated will change in direct proportion. The tiny voltage generated across the Hall Element will eventually be amplified and converted into the square wave signal voltage captured in the Example Waveform above

The Hall Effect Element is housed in the sensing tip of the CMP adjacent to a permannet magnet and in close proximity to the camshaft pick up. The rotation of the pick up will change the surrounding magnet field which in turn effects the tiny voltage generated across the Hall Element. The fluctuating tiny voltage is then amplified and converted as mentioned below.

Refer to vehicle technical data for specific test conditions and results.

The example waveform illustrates the square wave 5 V output signal from a Hall Effect CMP. An alternative output signal voltage of 12 V is also used across all manufacturers and so it is vital to check the relevant technical data to ensure the output voltage level is correct. Both styles of CMP will share a common ground level voltage of 0 V as indicated by the Signal Ruler (1) where the numerical value is represented in the Ruler Legend (6). N.B. There maybe occasions where the vehicle manufacturer raises the ground level of the Hall Effect CMP slightly above zero volts in order to reduce noise and improve self diagnosis. (refer to the vehicle technical data).

Unlike the inductive style CMP the amplitude of the Hall Effect CMP signal remains fixed (regardless of engine speed), however the frequency of the signal will increase in direct proportion to engine speed. The correct formation of the square wave signal is paramount to ensure efficent engine performance. Each square pulse is generated by the movement of the camshaft pick-up passing the sensing tip of CMP. Each pulse represents a single tooth, lug or drilling of the pick up which should therefore be uniform in structure, without deformation and identical in sequence.

Depending on manufacturer, numerous style pick-ups are utilised to denote one complete camshaft revolution. In the example wavefroms above three different pulse widths are used per camshaft revoution where other maufacturers may use one single pulse (a single lug) or multiple pulses denoting the precise camshaft postion in relation to firing order (refer to the vehicle technical data).

Fundamental to the correct operation of the Hall Effect CMP is the power supply and ground reference at the sensor. A typical CMP sensor connector consists of 3 wires, which can be memorised as “G.P.S” Ground (0 V) – Power (5 or 12 V) - Signal (5 or 12 V)

Both the power and ground are required to supply the integrated circuitry (IC) within the CMP which in turn is responsible for supplying stable current through the Hall Effect Element and converting the tiny voltage generated by the rotating pick up into a stable square wave output signal. 

Generic camshaft DTC's

P0010 A camshaft position actuator circuit (bank 1)

P0011 A camshaft position - timing over advanced or system performance (Bank 1)

P0012 A camshaft position - timing over retarded (Bank 1)

P0013 B camshaft position - actuator circuit (Bank 1)

P0014 B camshaft position - timing over advanced or system performance (Bank 1)

P0015  B camshaft position - timing over retarded (Bank 1)

P0016 - Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A

P0020 A camshaft position actuator circuit (Bank 2)

P0021 A camshaft position - timing over-advanced or system performance (Bank 2)

P0022 A camshaft position - timing over retarded (Bank 2)

P0023 B camshaft position - actuator circuit (Bank 2)

P0024 B camshaft position - timing over advanced or system performance (Bank 2)

P0025 B camshaft position - timing over retarded (Bank 2)

GT061-4

Disclaimer
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.

Suitable accessories

  • Premium 6-way breakout lead set

    £269.00

  • Back-pinning Probe Set

    £48.00

  • PicoScope Battery Clip

    £2.75

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Guided test: Camshaft sensor - hall effect