my subaru dealer told me l needed to replace the ecu in my vehicle because my check engine light is on. l took the car to a buddy of mine who has a code box and the only codes it throws is egr valve and knock sensor. im hesitant to take it to the dealer cause my check engine light has kept coming on and they've replaced tons of parts and wanna replace the knock sensor, ecu and egr valve. knock sensors and egr valve have been replaced a year ago. how do l know if my ecu is going bad?

The first thing u need to do is obtain the actual diagnostic trouble codes (DTCs) ur ECU is detecting, in the form Pnnn, where the n is r decimal digits. The second thing u need to do is to obtain an estimated cost from ur dealer for the repairs ur dealer is proposing.

Lastly, once u have obtained this data, call Subaru of America at 1-800-SUBARU3 (1-800-782-2783).

An ECU failure is extremely unlikely, unless you've crossed some wires during some aftermarket equipment installation while the battery was still inline.