information record will be stored in memory after the identified failure disappears (after
troubleshooting).
When a failure is identified for the first time, Hz will be set as its initial value 40. If
failure status does not change, then this numerical value will maintain all along.
Once it is identified that this failure has disappeared and the state has held for a certain
time, whenever the engine starts with success (its engine speed has exceeded the value
at end of starting) once, Hz will decrease by 1. At this point, ECU will believe that this
failure has disappeared, but the failure information record still exists.
If a failure (for example, as a result of poor contact) frequently appears and disappears,
then Hz will increase by 1, but will not exceed its given upper limit value 100.
If value of Hz has been decreased to zero, the failure information records in this failure
memory will be completely cleared.
5. Limp Home
For some identified significant failures, when duration exceeds the given
stabilization time, ECU will take appropriate software countermeasures, for example,
closing some control functions such as closed loop control of oxygen sensor etc. and
setting substituted values for some data that are considered to be suspect and so forth.
At this point, though the working condition of the engine is comparatively poor, the
auto can still run. The purpose to do this is to enable the auto limply run home or to a
service station for overhaul, so as to avoid the embarrassment that the auto breaks down
on highway or afield. Once it is identified that the failure has disappeared and Hz has
fell to below 40, use of normal data will be resumed again.
6. Failure Alert
In the electric control system, when failure take places in any of such important
parts as ECU, absolute pressure sensor in intake manifold, throttle position sensor,
coolant temperature sensor, knock sensor, oxygen sensor, phase sensor, injector, two
driver stages of step motor of idle speed actuator, canister control valve, or fan relay at
corresponding failure location, ECU will give an alarm through lightening of failure
indicator lamp until this failure location restores.
7. Readout of Failure
The failure information records can be called out of ECU through a trouble diagnosis
tester. If the failure relates to the function of mixed air (fuel and air) proportional
regulator, then the engine must at least run for 4 minutes before reading out failure
information records; especially for failure in oxygen sensor, be sure not to detect data
until the engine runs and warms up.
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