Variable camshaft timing control solenoid

The purpose of this test is to evaluate the correct operation of the variable camshaft timing control solenoid based on the switching voltage and duty control during engine run conditions.

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. Use manufacturer data to identify the control solenoid switched earth circuit.
  2. Connect PicoScope channel A to the control solenoid switched earth circuit.
  3. Minimise the help page and with the example waveform on your screen PicoScope has already selected suitable scales for you to capture a waveform.
  4. Start the scope to see live data.
  5. Start and run the engine, increase and decrease engine rpm for around 10 seconds.
  6. With your live waveform on screen stop the scope.
  7. Turn off the engine.
  8. Use the Waveform Buffer, Zoom and Measuring  tools to examine your waveform.


The solenoid has two terminals, both may have supply voltage at ignition on.

The switching frequency is dependent on engine system variations at the time of testing, temperature, RPM etc. The switching frequency and duration will also vary with different vehicle manufacturers.

Example waveform

Waveform notes

The Variable Camshaft Timing (VCT) solenoid is an actuator. It is commonly supplied with an ignition live (15 V) and a duty cycled ground provided by the engine management control unit. It has a duty cycle control from the engine management control unit.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select, Variable Camshaft Timing VCT solenoid voltage.

Example cam timing control valve

Further guidance

The use of VCT has become widespread throughout the automotive industry as the technology becomes cheaper and more manufacturers take advantage.

Variable camshaft timing is used to increase engine torque in the low engine speed range and to increase power in the high engine speed range. The use of VCT means that we may control the closing and opening times of inlet and exhaust valves. As a result VCT may also be used in place of an EGR (exhaust gas recirculation) valve.

Should you suspect a fault with the signal, test the wiring from the Powertrain Control Module (PCM) to the VCT actuator.

Ensure that the PCM has good power supplies and grounds where required or specified.


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


  • Back-pinning Probe Set


  • Flexible Back-pinning Probe


  • PicoScope Battery Clip


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Guided test: Variable camshaft timing control solenoid