Isuzu 4HL1, Workshop Manual

Page: 149 / 267

Engine Control System 1A-147
DTC46 - Exhaust Brake System Fault
Circuit Description
The exhaust brake is operated by the solenoid valve
on/off control and the resultant vacuum path open/
close action. When the solenoid valve is turned on, the
vacuum path is opened and the exhaust brake valve
works. When the solenoid valve is turned off, the
vacuum path is closed and the atmospheric pressure is
applied to release the exhaust brake valve. After the
exhaust brake switch is turned on and all the necessary
vehicle conditions are met, the VIM energizes (turns
on) the solenoid valve.
DTC46 will be set when the solenoid valve fails to
respond the on/off operation of the exhaust brake.
Major Faulty Event
• Inactive exhaust brake system and QWS
• Inactive ABS/ASR
Conditions for Setting the DTC
With the battery voltage at 20 V or more, the engine
speed at 500 rpm or more, and the exhaust brake
turned on, the solenoid valve is turned off or exhaust
brake turned off, the solenoid valve is turned on for 1
second.
Action Taken When the DTC Sets
• After the DTC is set, the ECM will illuminate the
CHECK ENGINE lamp (MIL).
• The exhaust brake system is disabled.
Conditions for Clearing MIL/DTC
When the system fails and the DTC is stored to the
ECM, even repairing the faulty portion will not clear the
DTC from the memory. To clear the DTC, conduct the
following steps.
0.5R
0.5
W
0.5
B
1.25
W/R 1.25
W/R 1.25
W/R 0.3
O/L
0.5
G/Y
0.5
B/W
0.85
B/O
0.3
BR/W
0.5
LG/B
Exhaust
Brake
Lamp Exhaust
Brake
VSV
VIM
(Vehicle
Interface
Module)
ECM
Glow
Lamp
ECO
Relay
Main Relay
Battery
Key SW
(ON)
Key SW
(START)
SBF
50A
SBF
50A
SBF
30A
SBF
100A
# 19
15A
# 22
10A
27 26 25 76 75 38 42 3 46 36 4 2
0.5 L/Y
0.5 L/Y
LNW21ALF005801-X