I have an 02 with AEM cai and APEX WS catback (installed: 700 miles) at 6250 miles check engine flash twice and then stay lite up. I was in second gear at 24 mph due to traffic jam. Car runs fine with the light on, no black smoke, no weird noise, no bogging, and no other noticeable car problem. I check the bypass valve and it was clog. How did I check it? Try to blow the direction of the flow of air and it was kind of hard to blow through it. Anybody, knows what might have cause to clog the bypass valve?

 

Check engine light or maintenance required light. If it's the latter, then the car is telling you to do your 1st oil change.