Innova 3100 Owner's Manual page 39

The "Malfunction Indicator Lamp" (MIL) is the accepted term
used to describe the lamp on the dashboard that lights to
warn the driver that an emissions-related fault has been
found. Some manufacturers may still call this lamp a "Check
Engine" or "Service Engine Soon" light.
There are two types of DTCs used for emissions-related faults: Type
"A" and Type "B." Type "A" codes are "One-Trip" codes; Type "B"
DTCs are usually Two-Trip DTCs.
When a Type "A" DTC is found on the First Trip, the following events
take place:
The computer commands the MIL "On" when the failure is first
found.
If the failure causes a severe misfire that may cause damage to
the catalytic converter, the MIL "flashes" once per second. The
MIL continues to flash as long as the condition exists. If the
condition that caused the MIL to flash is no longer present, the MIL
will light "steady" On.
A DTC is saved in the computer's memory for later retrieval.
A "Freeze Frame" of the conditions present in the engine or
emissions system when the MIL was ordered "On" is saved in the
computer's memory for later retrieval. This information shows fuel
system status (closed loop or open loop), engine load, coolant
temperature, fuel trim value, MAP vacuum, engine RPM and DTC
priority.
When a Type "B" DTC is found on the First Trip, the following events
take place:
The computer sets a Pending DTC, but the MIL is not ordered
"On." "Freeze Frame" data is not recorded at this time. The
Pending DTC is saved in the computer's memory for later retrieval.
If the failure is found on the second consecutive trip, the MIL is
ordered "On." "Freeze Frame" data is saved in the computer's
memory.
If the failure is not found on the second Trip, the Pending DTC is
erased from the computer's memory.
The MIL will stay lit for both Type "A" and Type "B" codes until one of
the following conditions occurs:
If the conditions that caused the MIL to light are no longer present
for the next three trips in a row, the computer automatically turns
the MIL "Off" if no other emissions-related faults are present.
However, the DTCs remain in the computer's memory for 40
warm-up cycles (80 warm-up cycles for fuel and misfire faults).
The DTCs are automatically erased if the fault that caused them to
be set is not detected again during that period.
OBD 2
Learning More
DIAGNOSTIC TROUBLE CODES (DTCs)
37