Electronic Throttle Control System Diagnostics

Most modern vehicles now use electronic throttle control systems, which are generally made up of two throttle position sensors on the throttle plate and two on the accelerator pedal.

This setup allows the vehicle’s computer to figure out where to open the throttle and means one sensor is used for main operation while the other is there as a backup.

But failing or faulty systems can cause issues such as false information being relayed to the car’s computer, poor running and performance, and warning lights being illuminated.

So testing the throttle control system should be part of your routine if a vehicle comes in with similar issues.

The Guided Component Tests included in the vehicle diagnostic software from Snap-on helps you check the system and identify any errors.

It’s like a lab scope with training wheels to help you through the steps you need.

Hook up your diagnostic tool – let’s use ZEUS for this example – and once the vehicle has been identified, head to the Fuel Injection menu within Guided Component Tests, click on Throttle Control System, then connect to the throttle position sensor and run a DC voltage test.

The software shows you what the connector looks like and how to connect your test leads, along with the known good measurements for your vehicle – you’re going to need those in the test.

Set up your meter view so that you can view two channels, which will mean you can see the data from both sensors.

Once you have done that then, with the vehicle’s key on but engine off, press the accelerator pedal a few times to actuate the throttle and generate some data.

Zoom in on the results and use the cursors to check the measurements during the actuation periods – these should be shown by the two lines rising in time with when the pedal was pressed.

The results can then be compared with the known good data and if what you’re seeing falls within the given boundaries you know the throttle position sensors are in good shape.

When you’re checking the graphs you want to make sure that there are no unexpected drop-outs or fuzziness. You will quickly be able to see in the pattern if this is happening.

So diagnosing a throttle position sensor issue needn’t be a huge challenge if it is an issue you find yourself facing.

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