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Quick Tip: Flex Ray Bus Diagnostics

Applies To: MODIS Edge™, MODIS Ultra™, TRITON-D8®, VANTAGE® Ultra, VERUS® Edge, VERUS® PRO, ZEUS®

Having a hard time diagnosing a no communication or vehicle network issue? There are many different types of networks on modern vehicles. In this Diagnostic Quick Tip, National Field Trainer Jason Gabrenas shows you how to use a lab scope to check the Flex Ray bus network system.



Vehicle communication issues can be a real bear to try and diagnose on some of these newer vehicles.

This BMW behind me right here has what they call a flex ray bus, which is a much faster bus than the CAN systems that we're used to.

We actually have a built-in test on any of our lab scopes using the guided component tests. Let's go in there and I'm going to show you how to do that.

Click on Guided Component Test. It [the vehicle] is an import, BMW, 2013, X5 three-litre. It's going to confirm our vehicle for us and then it's going to list a bunch of systems on the vehicle.

I want to go into the Fuel Injection System in order to test any of my communication networks. And about halfway down in the middle there is the flex ray bus, so we're going to click on that.

This lists a signature test for us. Over on the top left-hand side of the screen it shows us that our yellow wire has to go to signal one a; the green wire goes to signal one B, and the black goes to a known good ground.

On the right-hand side, it's going to show us what the connector looks like and where in that connector we need to probe.

It looks like pins 33 and 34 there. We already have it set up on the vehicle, so we can just scroll down a little bit further.

There's a nice picture of what the signature is supposed to look like and some voltage ranges over here on the left. So if I click view meter, it's going to open up the meter for us. And there is our signal.

This is what a good signal would look like on this flex ray bus. We're going to look for any shorts to ground.

So you'd see way down at the bottom it would say zero volts; it would be aligned going to zero volts. Or say if it was shorted to a five volt power, you would see a line up to five volts.

The nice thing about these communication networks is that they are usually right in the middle of that five volt to zero volt range, so you can tell pretty quickly if there's a short to ground.

So as you can see, by using the guided component tests, it gives you a really nice, quick, easy way to diagnose some of these no-communication issues on these network systems.

Last Updated: January 9, 2020

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