Variable camshaft timing adjuster waveforms

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.

How to perform the test

Plug the BNC test lead into Channel A on the PicoScope. Place a black clip onto the black probe (negative) and connect this to a suitable ground point. Connect a Back-pinning Probe to the coloured lead (positive) in order to backpin the connector at the variable camshaft timing adjuster, as illustrated in Figure 1. If a suitable automotive break-out lead is available, this may be used instead of the back-pinning method.

The adjuster will have two electrical connections: an ignition positive (15 V) and a switched earth.

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.

Technical information

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.

Faulty waveforms - troubleshooting

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

  • Back-pinning Probe Set


  • Flexible Back-pinning Probe


  • PicoScope Battery Clip


  • Large Dolphin/Gator Clips


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


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


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Guided test: Single variable valve timing (VVT)