Chapter
E
: Computerized Engine Control Diagnosis And Repair (Including OBD II)
110
alytic converter is a two trip monitor, with the additional
condition that the MIL will blink while the severe misfire
is occurring.
AUTOMATIC CLEARING: If the vehicle completes three
consecutive "good trips" (three consecutive trips in
which the monitor that set the DTC is run and passes),
the MIL will be turned off, but the DTC and freeze frame
will remain stored in ECM memory. If the vehicle com-
pletes 40 warm-up cycles without the same fault recur-
ring, the DTC and freeze frame are automatically cleared
from the ECM memory.
MANUAL CLEARING: Any stored DTCs and Freeze
Frame data can be erased using the scan tool, and the
MIL (if lit) will be turned off. Although it is not the rec-
ommended method, DTCs and Freeze Frame data will
also be cleared if the ECM power supply of the battery
is disconnected.
Monitor Readiness Status
The monitor readiness status indicates whether or not a
particular OBD II diagnostic monitor has been run since
the last time that DTCs were cleared from ECM and
TCM memory. If the monitor has not yet run, the status
will display on the Scan Tool as "Not Complete". If the
monitor has been run, the status will display on the scan
tool as "Complete". This does not mean that no faults
were found, only that the diagnostic monitor has been
run Whenever DTCs are cleared from memory or the
battery is disconnected, all monitor readiness status in-
dicators are reset to "Not Complete". Monitor readiness
status indicators are not needed for the Comprehensive
Component, Fuel Control, and Engine Misfire monitors
because they run continuously. The readiness status of
the following system monitors can be read on the scan
tool:
Oxygen Sensors
Oxygen Sensor Heaters
Catalytic Converter
EGR System
EVAP System
Variable Valve Timing
Engine Thermostat
Warm-Up Cycle
Warm-up cycles are used by the ECM for automatic
clearing of DTCs and Freeze Frame data. To complete
one warm up cycle, the engine coolant temperature
must rise at least 40°F (22°C) and reach a minimum of
160°F (71°C).
Trip
A trip is a key-on cycle in which all enable criteria for a
particular diagnostic monitor are met and the diagnos-
tic monitor is run. The trip is completed when the igni-
tion switch is turned off.
Drive Cycle
Most OBD II diagnostic monitors will run at some time
during normal operation of the vehicle. However, to sat-
isfy all of the different trip enable criteria and run all of
the OBD II diagnostic monitors, the vehicle must be dri-
ven under a variety of conditions. As an example, the
following drive cycle will meet the enable criteria to allow
all monitors to run.
1. Ensure that the fuel tank is between 1/4 and 3/4 full
2. Start cold (below 86°F / 30°C) and warm up until
engine temperature is at least 160°F (71°C) - one
minute minimum
3. Accelerate to 40-55 mph at 25% throttle and main-
tain speed for five minutes
4. Decelerate without using the brake (coast down) to
20 mph or less, then stop the vehicle. Allow the en-
gine to idle for 10 seconds, turn the key off, and
wait one minute
5. Restart and accelerate to 40-50 mph at 25% throt-
tle and maintain speed for two minutes
6. Decelerate without using the brake (coast down) to
20 mph or less, then stop the vehicle. Allow the en-
gine to idle for 10 seconds, turn the key off, and
wait one minute.
Summary of Contents for ASE-A8
Page 2: ......