Diagnostic Trouble Codes Stored; Clearing Diagnostic Trouble Codes - Isuzu 4HL1 Workshop Manual

Diagnostic Trouble Codes Stored

Code 12 that is displayed three times and then stored
code is displayed three times. When multiple DTCs are
stored, each code is displayed three times, starting
from the lowest number. After all DTCs are displayed,
above sequence is repeated from code 12 as long as
DLC is being shorted.
eg.,) Display Start Cord "12"
Display Start
Turn On
Turn Off
eg.,) Trouble Cord "21"
Display Start
Turn On
urn Off
eg.,1 : Diagnostic Trouble Codes not Stored
12 12 12
eg.,2 : Diagnostic Trouble Codes "21", "24" Stored
12 12 12

Clearing Diagnostic Trouble Codes

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
steps listed below.
• Keep the starter switch turned on and the engine
turned off.
• Short the data link connector.
Perform the following steps.
1. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
2. Turn on the idle position switch for not less than 1
second but not more than 3 seconds. (Release the
accelerator pedal.)
3. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
0.4
3.2 1.2
0.4 0.4
3.2 1.2
12 12 12 12
21 21 21 24
0.4
3.2
3.2
12 12 12 12
24 24 12 12
4. Turn on the idle position switch for not less than 1
second but not more than 3 seconds. (Release the
accelerator pedal.)
5. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
6. After the above operations are properly completed,
the CHECK ENGINE lamp (MIL) illuminates for 3
seconds to report the memory is cleared.
7. Turn off the starter switch. Wait for 5 seconds and
turn on the starter switch again.
When Tech 2 has been connected to the vehicle, the
DTC can be cleared through the memory clear
operation with Tech 2.
Engine Control System 1A-43
12 12 12 12
12 21 21 21
Unit (sec)
Unit (sec)
Endless Display
Endless Display
LNW21AMF000601-X