Launch BST580D User Manual page 23

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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 may or may not be saved at this time depending on
manufacturer. 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 as a history code 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.
• Misfire and fuel system faults require three trips with "similar conditions"
before the MIL is turned "Off." These are trips where the engine load, RPM
and temperature are similar to the conditions present when the fault was
first found.
Note: After the MIL has been turned off, DTCs and Freeze Frame data stay
in the computer's memory.
• Erasing the DTCs from the computer's memory can also turn off the MIL. If
a Diagnostic Tool or Scan Tool is used to erase the codes, Freeze Frame
data will also be erased.
BST580D User's Manual
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