Functional Tests

The Functional Tests selection is used to access vehicle‑specific subsystem and guided component tests. Available tests vary by manufacturer, year, model, and only the available tests display in the menu.

Getting Started Video

Functional Tests Opens in a new tab.

Follow all instructions while performing tests or resets.

Do not enter any functional tests while driving on a road test. During some functional tests, the ECM makes changes to ignition timing, fuel delivery, and other engine functions, which may affect engine operation and vehicle control.

How and what information is presented on the screen varies according to the type of test being performed.

There are four types of functional tests:

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Information Tests—are read-only tests, like selecting “VIN” from a Functional Tests menu to display the VIN of the identified vehicle.

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Toggle Tests—switch a component, such as a solenoid, relay, or switch, between two operating states.

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Variable Control Tests—command a certain value for a system or component, such as varying the spark timing in 1° increments or the EGR valve duty cycle in 10% increments.

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Reset Tests—reset the adaptive, or learned, values that are stored in the electronic control module.

Typical functional test options may include:

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CKP Variation Learn

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EVAP Service Test

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Injector Balance

Selecting a Functional Test opens the test. A typical test includes on-screen instructions followed by a test screen that provides a changeable value or switch that is manually entered or actuated on-screen and a list of displayed PID(s) to monitor their behavior while performing the test.

Sample functional test controls

Functional test controls allow you to activate/deactivate or change the test signal. The controls will vary depending on the test, a few examples are shown in the following table.

Icon	Description
Test	Activates the test.
Change List	Allows you to switch data lists.
Custom	Allows you to select which parameters display during the functional test.
Minus	Switches an item to low or off, or incrementally reduces a variable signal.
Plus	Switches an item to high or on, or incrementally increases a variable signal.

Functional Resets and Procedures

Functional Resets allow you to manually reset certain control module values (e.g. reset fuel trim values, or turn off the oil change indicator) directly from the diagnostic tool (if supported by the vehicle).

Functional Resets Procedures are step-by-step instructions to guide you though an on-vehicle reset procedure. These instructions maybe provided in certain applications (if available) when on-tool functional resets are not supported.

Functional resets are not available for all vehicles, and will vary depending on vehicle support. A screen message may display “Functional Reset is not available for this vehicle”.