When you start your vehicle, the check engine light comes on momentarily to test the engine/emission control system and bulb. The system is self-diagnostic and the light is a way to communicate trouble. The system is designed to function in a "limp home" mode when trouble occurs and the light comes on - and stays on. However, take your vehicle to an authorized Subaru dealer right away. The technicians have specialized tools and training to access trouble codes stored in the vehicle's memory each time the light is illuminated. This is a sophisticated system, with the ability to detect and store information about even the slightest changes.
One item which may seem insignificant but which can cause the system to detect trouble is a loose or missing fuel filler cap. Remove the cap, then tighten it until it clicks. If you are unsure whether the loose cap was the cause or if the light stays on, visit your Subaru dealer.
The light also can come on if you have installed electrically powered accessories (such as a radar detector or keyless entry system) that aren't compatible with your vehicle's systems. If the light comes on and such accessories are installed, Subaru technicians may insist they be removed or disconnected before any further diagnosis can take place. Subaru-approved accessories are thoroughly tested to prevent such problems.
For more information, check your Owner's Manual.
Brought to you by the Winter 2002 issue of Drive Magazine.