VVT actuators - Dual variable valve timing

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 onto the black plug (negative) and connect this to a suitable ground point. Connect a Back-pinning Probe to the coloured plug (positive) in order to backpin the connector at the variable camshaft timing adjuster on the Inlet Camshaft Actuator, as illustrated in Figure 1.

Plug a second BNC test lead into Channel B on the PicoScope. Place a black clip onto the black plug (negative) and connect this to a suitable ground point. Connect a Back-pinning Probe to the coloured plug (positive) in order to backpin the connector at the variable camshaft timing adjuster on the Exhaust Camshaft Actuator.

If you have a 4-channel automotive scope you can also check the ground wires from the actuators by connecting the leads as follows:

Plug a third BNC test lead into Channel C on the PicoScope. Place a black clip onto the black plug (negative) and connect this to a suitable ground point. Connect a Back-pinning Probe to the coloured plug (positive) in order to backpin the ground wire of the connector at the variable camshaft timing adjuster on the Inlet Camshaft Actuator.

Plug a fourth BNC test lead into Channel D on the PicoScope. Place a black clip onto the black plug (negative) and connect this to a suitable ground point. Connect a Back-pinning Probe to the coloured plug (positive) in order to backpin the ground wire of the connector at the variable camshaft timing adjuster on the Exhaust Camshaft Actuator.

If a suitable automotive break-out lead is available, it may be used instead of the back-pinning method.

Each actuator has two electrical connections: an ignition positive and a ground (earth).

Waveform notes

The Variable Camshaft Timing (VCT) solenoid is an actuator. It is commonly supplied with an ignition live and a ground provided by the ECM. Note that either the positive or the ground duty cycle can change depending on the design of the system by the OEM.

You can compare the duty cycles of both actuators with each other and against manufacturer's information, but you may need to load the engine to make the duty cycle of the exhaust actuator change with engine operating parameters and EGR conditions.

Technical information

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

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 can 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.

AT156-2

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

Share your experience

If you have any suggestions to improve this guided test please do so using the 'add comment' button.

Add comment

Your email address will not be published. Required fields are marked *

Guided test: Dual VVT