Camshaft sensor - AC excited type

The purpose of this test is to evaluate the correct operation an AC excited camshaft sensor based on the AC voltage supply and AC voltage return signal during engine run conditions.

How to perform the test

View connection guidance notes.

1. Use manufacturers data to identify sensor circuit functions. The sensor has three wires, one carrying the AC voltage input signal, a second the AC voltage output signal and a third earth cable.
2. Connect PicoScope Channel A. to the input signal circuit.
3. Connect PicoScope Channel B. to the output signal circuit.
4. Start the engine and allow it to idle.
5. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
6. Start the scope to see live data.
7. With your waveforms on screen stop the scope.
8. Turn off the engine.
9. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.

Example waveform

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.

Further guidance

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.

GT013-5