12-8 FI SYSTEM DIAGNOSIS
VOLTAGE CHECK
If voltage is supplied to the circuit being checked, voltage check
can be used as circuit check.
• With all connectors/couplers connected and voltage applied
to the circuit being checked, measure voltage between each
terminal and body ground.
If measurements were taken as shown in the figure at the right
and results are as listed below, it means that the circuit is open
between terminals
A
and
B
.
Voltage Between:
C
and body ground: Approx. 5 V
B
and body ground: Approx. 5 V
A
and body ground:
0 V
Also, if measured values are as listed below, a resistance
(abnormality) exists which causes the voltage drop in the circuit
between terminals
A
and
B
.
Voltage Between:
C
and body ground: Approx. 5 V
B
and body ground: Approx. 5 V
2 V voltage drop
A
and body ground:
3 V
SHORT CIRCUIT CHECK (WIRE HARNESS TO GROUND)
• Disconnect the connectors/couplers at both ends of the circuit
to be checked.
NOTE:
If the circuit to be checked branches to other parts as shown,
disconnect all connectors/couplers of those parts. Otherwise,
diagnosis will be misled.
• Measure resistance between terminal at one end of circuit (
A
terminal in figure) and body ground. If continuity is indicated,
there is a short circuit to ground between terminals
A
and
C
.
1
Other parts
*1 To other parts
5 V
0 V
5 V
5 V
*1
5 V
