If the AMM is bad the CEL should be lit up and a code present.

They can be sparyed clean with CRC MAF (use no other) cleaner sometimes. I'd try that before a junkyard part.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)