Maintenance Manual for Chery·Windcloud
MOTOROLA EFI System
Chapter Two: Basic Principle for EFI System Failure Diagnosis
(1). Failure Information Record
Electronic control unit constantly monitors sensors, actuators, relevant circuits, fault
indicating lamp and accumulator voltage, etc. and even electronic control unit itself, and
carries out reliability test on sensor output signal, actuator drive signal and internal signal (for
instance: oxygen closed-loop control, knocking control, idle speed control and accumulator
voltage control). Once a certain link is found failed, or a certian signal value is unreliable,
electronic control unit will make information record of failure immediately in failure
memorizer of RAM. Failure information record will be stored in form of failure code, and
displayed as per sequence of failure occurrence.
Failure, according to frequency of occurrence, can be divided into “constant failure” and
“random failure” (for example: failure caused by temporary wire harness open circuit or
poor contact of socket connector).
(2). Failure Status
If the continuance of an identified failure exceeds the stabilization time stipulated for the first
time, ECU collects it as a stable failure, and stores it as “constant failure”; if such failure
disappears, ECU stores it as “random failure” and “nonexistent”; if such failure is identified
again, then still it is “random failure”, but the “existent” history failure does not impact the
normal use of engine.
(3). Failure Types
Short circuit to power supply anode
Short circuit to on ground
Open circuit (on occasion that input stage has upward pull/downward pull resistor, ECU will
identify the open circuit failure at input port as input port failure of short circuit to power
supply anode or short circuit to ground)
Signal unreliable
(4). Four Types of Failure
Max. failure, signal exceeds upper limit of normal range.
Min. failure, signal exceeds lower limit of normal range.
Signal failure, no signal.
Illogical failure, signal exists, but illogical.
(5). Limp Home
For some important failure identified, whose duration exceeds stabilization time stipulated,
ECU will adopt software countermeasure as appropriate to maintain operation of engine and
avoid breaking down of vehicle on the road.
(6). Failure Alarm
MOTOROLA EFI system has fault indicating lamp. In case failure occurs with relevant
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