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Engine Working Data Flow Displayed by Diagnostic Apparatus
Analyze and determine engine fault using the
engine working data flow displayed by the diagnostic
apparatus.
Step I
a) Engine harness and the vacuum pipeline—may affect
the system to control air flow and fuel supply
b) Whether oxygen sensor is assembled in place—may
affect the system to determine the air to fuel ratio
c) Engine fault indicator—may affect the system to
give an alarm for fault
d) Storage battery voltage—determine whether the
power of storage battery is sufficient
e) Determine whether coolant temperature sensor,
intake temperature sensor, intake manifold absolute
pressure sensor and oxygen sensor display value are
normal
f) Working range of throttle position sensor—it cannot
be fully opened or closed, which may affect engine
power performance and some system functions
Step II
Check whether ECU power is turned off—the
communications between diagnostic apparatus and
system is interrupted after turning off key switch.
Step III
a) Storage battery voltage (14V) —Indicate whether
the generator is working properly.
Too high: there may be fault in voltage regulator;
Too low: there may be improper connection of
generator or generator fault
b) Intake manifold pressure—it can predict whether
there is leakage in intake and valve clearance
problems
Valve clearance is too small: this value is too high,
so engine power performance may be affected; in
addition, due to too early opening of exhaust valve
and increase in exhaust temperature, oxygen
sensor and three-way catalytic converter service
life may be significantly shortened;
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