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Multi-Channel Cam/Crank Correlation Test

Have you ever run into a situation where you needed to check a vehicle’s timing quickly and easily?

Snap-on diagnostic tools and software let you do just that by using a lab scope and performing a multi-channel cam/crank correlation test.

One of the great things that you can do with a lab scope is compare relationships between multiple sensors on a vehicle.

For the purposes of this demonstration, let’s use a 2013 BMW X3, which has two different cam sensors and a crank sensor.

If you ever had a suspected timing issue or something like that, you can go in with your scan tool and compare to the relationships between the three things, so let's walk through how we do that.

With the lab scope hooked up and set for three channels, the crank sensor is on channel one, the intake cam sensor on channel two and the exhaust cam sensor is on channel three.

Fire up the vehicle and you can then see the pattern as shown on your scan tool’s screen. Zoom out far enough so that you can see one revolution of the engine.

There’s a blank spot dead centre on the crank, and you can also see how the intake cam and exhaust cam time out against each other and see the correlation between the three.

So if you have a cam timing problem, you could also do this with one single cam sensor and a single crank sensor.

But if you have some sort of timing issue that you want to look at, check the correlation between them and that should help you diagnose it.