What's up guys. I scanned my buddies CEL on his 03 Rav4 after it came on during his drive home from work. It was throwing a P0420 (catalyst system efficiency below threshold bank 1), and code P0430 (catalyst system efficiency below threshold bank 2). I cleared the codes, and immediately checked the continuity of all 4 sensors. They are all good. I understand the possibility of a lazy sensor, so I cleaned the connectors and started the car again. It immediately threw another CEL, and this time there were 4 codes. The original P0420 and P0430, and now also P1310 (coil pack #3), and P0300 (multiple misfire detected). The car is running fine, no noticeable loss of power or gas mileage, or a rough idle. All 4 coils were replaced within the last year or so. I decided to check all of the coil packs anyway and they are fine. Within the last 3 years he has also installed new catalytic converters, 02 sensors, and a new ECM. The only thing I could think to check is the MAF sensor, and its clean and seems to be operating fine. Any ideas on what could be tricking the ECM into thinking that it's having these problems, or anybody ever seen anything similar? Any help is much appreciated, I'm stumped. Thanks a lot guys.