in the component, or the sensor circuit the
Circuit Shorted to Power:
controller no longer receives a "normal" signal.
"Abnormal" signals received by a controller mean
1. Complex circuits can fail in numerous ways. Circuits
part of the circuit has a malfunction.
can short to other circuits causing components to
Sensor circuits can fail in numerous ways. Service
operate when unrelated switches are turned ON. In
Codes will be generated when sensor circuits fail.
the example if switch S1 is ON and wires are
Controllers may allow the component to operate
shorted at (G) light E1 and E2 will be ON.
normally, may allow operation in a reduced capacity
2. Components can operate even when all switches
such as a "limp home mode", or the controller may
are OFF. In the example if wires are shorted at (E),
prevent any component operation.
light E2 will be ON all the time.
If a sensor circuit signal wire (N) shorts to a ground
3. Components can operate strangely. In the example
wire, a "Short to Ground" Service Code may be
if wires are shorted at (H), fuse F1 will blow when
switch S1 is turned ON. If switch S2 is turned ON,
If a sensor circuit voltage wire (O) shorts to ground,
light E2 will operate normally and light E1 may be
a Service Code may or may not be generated, but
very dim, or light E1 and E2 may be dim, even if
other sensors connected to the controller will cease
fuse F1 is blown.
to work, because their supply voltage will also be
shorted to ground. Erratic operation of the monitor
Sensor Circuit Shorted to Itself:
If a sensor circuit voltage wire (P) shorts to the
1. Sensors are part of a controller circuit. Controllers
sensor signal wire a Service Code may or may not
are used to operate components like engines,
be generated. The controller may receive a signal
transmissions or hydraulic systems. Sensors send
indicating the sensor is reading its maximum upper
information such as speed, pressure or temperature
or lower limit.
from the component to the controller to monitor
operation of the component. If a malfunction occurs
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