- The outputs that can be tested and the sequence in which they become active are controlled strictly by the control module.
- If you start the output test and get back to main menu of control unit test sequence will still be active.
- Most control modules will permit the output test sequence to be run only one time per session. If you need to run the sequence again, you must cycle the key OFF and ON.
- Some output tests require additional action before they become active. Fuel injectors are a common example. To activate a fuel injector you must press (and in some cases release) the gas pedal. Exact details can be found in your factory repair manual.
- On most systems the output test function is only available when the engine is not running.
- It is normal to see a "short to ground" message in the process of running output test. The ECU identifies which output it is currently testing by sending a fault-code number. On many ECUs the full text for this fault code includes "short to ground". Why? Because one side of the actuator in question has 12V on it all the time and the ECU completes the circuit (and turns the actuator on) by pulling the other side to ground.
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The Output Test function is used to test a control module's electrical outputs (and the wiring that connects it to the various devices). To access the function follow the instructions:
Do not use the output test function on any system while the car is in motion. Running output test on the ABS brake system can temporarily disable the brakes entirely and cause individual wheels to lock and unlock.
We suggest you refer to the factory repair manual for your specific car before running output test on any control module so you will know what to expect.
Running output test on the airbag control unit can lead to unexpected results such as a vehicle not starting. Running output test is supposed to make the airbag controller generate a simulated crash signal to the rest of the systems in the vehicle so that unlocks itself and shuts various things OFF.