Isuzu 1999 RODEO Workshop Manual page 2268

8D–118 WIRING SYSTEM
Diagnosis
Horn Do Not Sound
Step
1 Is the fuse 2 normal?
2 Remove the horn relay.
Is the battery voltage applied between horn relay
harness side connector I–41 terminal 2 or connector
I–42 terminal 2 and the ground?
3 Repair an open circuit between the fuse 2 and
connector I–41 terminal 2 or connector I–42 terminal 2.
Is the action complete?
4 Connect the battery positive terminal with the horn
relay side connector I–41 terminal 2 or connector I–42
terminal 2 and the negative terminal with connector
I–42 terminal 20 or 15.
Is there continuity between horn relay side connector
I–41 terminal 2 and 1 or connector I–42 terminal 2 and
connector I–41 terminal 4?
5 1. Disconnect the horn switch connector I–49.
2. Press the horn switch.
Is there continuity between the switch side connector
I–49 terminal 1 and the ground?
6 Is there continuity between harness side connector
I–42 terminal 20 or 15 and harness side connector I–49
terminal 1?
7 Repair an open circuit between connector I–42
terminal 20 or 15 and connector I–49 terminal 1.
Is the action complete?
8 Repair an open circuit between the horn relay and the
horns.
Is the action complete?
Horn Do Not Shut Off
Step
1 Disconnect the horn connector C–12 or C–14.
Is the battery voltage applied between harness side
connector C–12 or C–14 terminal 1 and the ground?
2 Disconnect the horn switch connector I–49.
Is there continuity between switch side connector I–49
terminal 1 and the ground?
3 Repair a short circuit between the horn relay and the
horn switch.
Is the action complete?
Action
Action
Value(s) Yes
— Go to Step 2
Approx. 12V Go to Step 4
— Go to Step 2
— Go to Step 5
— Go to Step 6
— Go to Step 8
— Verify repair
— Verify repair
Value(s) Yes
Replace the
Approx. 0V
relay
Repair or
replace the
switch
—
— Verify repair
No
Replace the
fuse
Go to Step 3
—
Replace the
relay
Repair or
replace the
switch
Go to Step 7
—
—
No
Go to Step 2
Go to Step 3
—