AC excited camshaft sensor

You will require a PicoScope to perform this test. A list of suitable accessories can be found at the bottom of this page.

How to perform the test

Plug a BNC test lead into Channel A on the PicoScope, place a black clip on the test lead with the black moulding (negative) and a Back-pinning Probe onto the test lead with the coloured moulding (positive). Plug a BNC test lead into Channel B on the black clip, and place a Back-pinning Probe onto the test lead with the coloured moulding (positive).

Place the black clip on the battery negative and probe the sensor with the two Back-pinning Probes.

The sensor has three wires, two carrying the alternating current (AC) waveform illustrated in the example on this page, the other wire an earth.

Example waveform (5 V)

Waveform notes

This type of sensor is used on some of the GM/Vauxhall/Opel ECOTEC engines. This Cylinder Identification (CID) sensor differs in operation from the other inductive sensors by having an Alternating Current (AC) voltage supply to the CID sensor. The Electronic Control Module (ECM) supplies a high frequency of 100 to 150 kHz (100,000 to 150,000 cycles per second) to an exciter coil that is located close to a rotating disc.

The disc is located at the end of the camshaft and has a section removed that, when aligned with the sensor, allows the frequency to excite the receptor (through mutual inductance) and returns the signal to the ECM, indicating the position of number 1 cylinder.

As the frequency is so fast, the time scale should be set to 20us/division so that the oscilloscope can capture the frequency.

The CID sensor is used as a reference by the ECM to determine the camshaft's position, from which the correct timing for the sequential fuel injection can be determined.

Technical information

This camshaft sensor differs in operation from the other sensors by having an Alternating Current (AC) voltage supply. The ECM supplies a high frequency of around 100 to 150 kHz to an exciter coil that is located close to a rotating disc.

The disc is located at the end of the camshaft and has a section removed that, when aligned with the sensor, allows the frequency to excite the receptor (through mutual inductance). The signal returns to the ECM, indicating the position of number 1 cylinder.

AT013-2

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

  • Back-pinning Probe Set

    £48.00

  • Flexible Back-pinning Probe

    £7.00

  • PicoScope Battery Clip

    £5.00

  • Large Dolphin/Gator Clips

    £10.00

  • Premium Test Lead: BNC to 4 mm, 3 m

    £48.00

  • Premium Test Leads: Set of four leads 3 m (TA125 - TA128)

    £179.00

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Guided test: Camshaft sensor - AC excited type