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What is bi-directional control? How can an Innova scan tool help me?

By R&D
Published on January 3rd, 2024

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What is bi-directional control?

Most enhanced automotive scan tools have bi-directional control ability, but technicians and DIY mechanics often only use the tool to read diagnostic trouble codes and examine parameter data. Bi-directional control describes the action of sending and receiving information between two devices. Modern vehicles with computer control systems are designed so that an OBD2 scan tool can request information or relay commands for specific tests and functions. Sometimes bi-directional controls are also called actuator tests, functional tests, system tests, or something similar. Reprogramming is also a part of bi-directional controls.

A bi-directional scanner is different from a regular OBD2 scanner. These scanners don't just retrieve information from the vehicle computer systems but also allow for commands. This is what bi-directional control entails. By performing active tests, a mechanic can find out what isn't working as it should. For example, bi-directional controls allow you to turn relay fans on and off or turn the fuel pump on and off to test for abnormal operation.

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These are examples of bi-directional tests that support a 2016 Chevy Silverado V8 5.3L engine from our coverage checker. Only our 5610, 5160RS, and tablet models support bi-directional testing.

Note: https://www.innova.com/pages/coverage

This video shows an example of the bi-directional capabilities the Innova 5610 offers. A purge valve diagnosis is being performed.

Another example of a bi-directional active test the Innova 5610 can perform.

Benefits Example:

  • Reduce diagnostic time by performing specific tests to measure the functionality of various components.
  • Narrow down part or system problems by switching functions on and off through bi-directional tests.

Use Case:

It's common for a Malfunction Indicator Light (MIL) / Check Engine Light on a vehicle to illuminate without any obvious sign of what might be wrong. A regular OBD2 diagnostic tool might return a diagnostic trouble code (DTC) showing that the Evap Purge Solenoid Circuit is causing the MIL.

Using the bi-directional controls, the purge valve is commanded open. The expectation is that fuel trim values should change based on what's in the gas tank. The fuel trim should decrease if the tank has a high concentration of fuel vapors. If there is a high concentration of oxygen, then the fuel trim should increase.

With the purge valve commanded open, there is no change in fuel trim. To confirm this figure, the purge valve is commanded open and shut several times. The fuel trim levels increase by the third time, indicating an open solenoid.

Based on this, the solenoid is sticking and should be replaced.

Examples:

  • The vehicle's MIL is illuminated.
  • You don't know what's wrong, but the DTC shows Evap Purge Solenoid Circuit.
  • Using the bi-directional controls on your Innova scan tool, you command the purge valve to open.
  • The fuel trim levels don't change as they should, so you command the purge valve open and shut.
  • On the third try, the fuel trim levels change, showing that the purge solenoid is sticking.
  • Now you know that the purge solenoid needs to be replaced.
  • This is a very specific problem that could have several reasons, and manual testing could require up to six steps to complete.

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