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Quick Tip: Electronic Throttle Control System Diagnostics

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

Electronic Throttle Control systems on newer cars can be tough to diagnose if you don’t know what to look for. In this Diagnostic Quick Tip, National Field Trainer Jason Gabrenas shows you how to check the sensors on Electronic Throttle Control systems using a lab scope.



A lot of newer vehicles use an electronic throttle control system which works very similarly to the older systems with the cable and a single throttle position sensor.

But on these newer vehicles it's two throttle position sensors that are on the throttle plate and two sensors that are actually on the accelerator pedal and that allows the computer to figure out where to open the throttle. They actually use one as a main sensor and the other one as a backup sensor.

Let's go over to our Guided Component Tests and see how we're going to test these things. This is kind of like our lab scope with training wheels.

So you go into the Fuel Injection System and we go to the Throttle Control System. I already have this hooked up to the throttle position sensor, so we'll do a DC voltage test on that.

You can see here it gives us what the connector looks like on the right-hand; it side shows us how to connect our test leads on the left-hand side.

If I hit view meter, it's going to bring up one channel, but like I said, there's two throttle position sensors here, so I'm going to show you a little bit of a power user tip.

Over on the bottom right -hand corner of the screen, there's a little icon that looks like two arrows. If I click it a couple of times, it's going to make it so I can set up additional channels on this unit.

So we'll do 10 volts there, 10 volts there. Then if I click it again, you can see now I have two lines on the same screen.

Now that I have this all set up, I'm going to go into the car, actuate the throttle a few times and see what we can get for a pattern.

Let's just pause it real quick and I'm going to zoom out, check my pattern. It looks like a good one there.

Zoom in and now I need to turn on my cursors to make some measurements. I'll click Cursors, Show, put one there, one there, and see what I get for measurements.

We're going to look up here and see what the specs tell us it's supposed to be.

So key on, engine off with throttle fully closed on sensor one should be about half a volt to 1.2 volts. We're getting 0.81 volts fully closed, so that's good. Full open should be about 3.2 to 4.9 and I'm getting 4.07 so that's pretty good.

Signal two, the throttle fully closed should be 2.1 to 3.1 volts. I have 2.39 volts. That's good. Full open should be four and a half to five volts. We're seeing an even five volts there. So both of these throttle position sensors are good.

When you're sweeping them back and forth, you want to make sure you don't see any drop-outs to ground or any sort of weird noise or fuzziness.

Just like an older style throttle position sensor, it's just a little potentiometer. If you've got a drop-out you'll notice it right in the pattern.

So that's a pretty quick and simple way, as you can see of just easily diagnosing a throttle position sensor issue.

Last Updated: January 11, 2020

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