Isuzu 4HL1, Workshop Manual

Page: 52 / 267

1A-50 Engine Control System
Inactive CHECK ENGINE Lamp Check
Circuit Description
After the starter switch is turned on, the CHECK
ENGINE lamp (MIL) is lit for 5 seconds and then turned
off. The power is supplied to this lamp from the battery
via the starter switch.
The ECM recognizes the ON signal from the starter
switch and turns on the CHECK ENGINE lamp.
Diagnostic Aids
An intermittent may be caused by a poor connection, a
rubbed-through wire insulation, or a wire broken inside
the insulator. Check for the following conditions and, if
a fault is found, perform repair or replacement.
• Poor connection at ECM: Inspect harness
connectors for backed-out pins, improper mating,
broken locks, improperly formed or damaged pins,
and poor pin-to-wire connection.
• Damaged harness: Inspect the wiring harness for
rubbed-through wire insulation or wire broken
inside the insulator.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2: When other lamps in the meter are turned on, the
power circuit from the battery to the CHECK ENGINE
lamp is sound.
ECM
(Engine
Control
Module)
CHECK
ENGINE
Lamp
LNW21ALF006001-X
121 120 119 95 87
118 117 116 115 114 113 109
0.25B 1.25B 1.25B 0.75B
0.5B
3W/G
2W/G
1.25W/R 0.5B/W 0.75B/O 1.25W/R 1.25W/R 0.5L/Y
99
0.5Y/B 0.5L/Y 0.5SB 0.5GR/W
112 88
Battery
DLC
Glow
Relay
Glow
Relay
IG
(ST)
IG
(ON)
SBF
50A
SBF
100A
3W/L
0.5B
SBF
50A
SBF
30A
SBF
60A
#19
15A
#22
10A
Main
Relay