actually i dont know. My CEL is not on and I went to Autozone today to see why my car is acting up, they hooked up the scanner and it showed it passing. Go figure. I think it is the DPFE sensor going bad
A fault code it only thrown for an emissions code or if another controller (ie...TCM) requests it to be turned on.
to the computer, a trip is defined as when a vehicle fits into a certain set of parameters...there is often a timer involved but there are also many other factors like engine speed, MAP voltage, that fit into a set of code enable conditions.
all codes that turn the lamp on are two-trip codes meaning the fault must occur twice in different enabling checks and they stay in memory for 40 vehicle drive cycles. the first time it fails it sets a pending code and the lamp lights the second time.
the exception for this is the misfire monitor that sets a lamp and a code immediately and stays in memory for 80 cycles.