Isuzu N-Series. Manual — part 454
6E-152 EMISSION AND ELECTRICAL DIAGNOSIS
Troubleshooting
Caution taken in inspecting
1. In inspecting system, write down Diagnostic Trouble Code (DTC) to be indicated.
(especially, when plural self-diagnosis codes are indicated.)
2. Before eliminating the indicated DTC by a memory clear switch, doubly inspect abnormal place as indicated in
DTC.
Inspection Procedure Flowchart (Diagnostic System Check)
Notice:
Please note that some items of DTC may not be generated unless the engine is warmed up or unless the vehicle is
driven under load.
Self-diagnosis Functions
Memorization of diagnostic trouble code
The self-diagnosis code indicated will be memorized in
Electronically Erasable Programmable Read Only Mem-
ory (EEPROM) with in the Engine Control Module
(ECM).
Accordingly even if the starter switch turns off or the
ECM is removed from the vehicle, the memorized self-
diagnosis code will not be eliminated.
* Unless an elimination procedure is taken, the diagnos-
tic trouble code (DTC) will remain in memory. (The
memory will be eliminated only by a memory clear
switch.)
Elimination of diagnostic trouble code
The DTC memorized in the EEPROM with in the ECM
can be eliminated only by the operation of the memory
clear switch. The elimination method memory clear
switch will be described below:
N6A1297E
EMISSION AND ELECTRICAL DIAGNOSIS 6E-153
1. Turn OFF ignition switch.
2. Use 4.7k
Ω resistance and make short circuit on
memory clear switch.
3. Turn ON ignition switch. The indication lamp turn
on (lighting) continuously after three seconds
flashing the indication lamp.
4. Turn OFF ignition switch.
5. Remove shortage resistance from memory clear
switch.
Location of the Memory Clear Switch
Location of the Memory Clear Switch (Diagnosis Connector)
How to read flashing of the indicator lamp:
The two-digit diagnosis code flashes starting from ten’s
figure to indicate the diagnosis code.
Please read the diagnosis code from the flashing.
If the plural diagnosis codes are indicated, the same di-
agnosis code is flashed repeatedly in steps of three
times.
Please read it correctly.
• Diagnostic Trouble Code (DTC) outputting is done
in decreasingly order of DTC number.
• Indication is changed over on completion of output
DTC indication.
• DTC indicator is stopped with diagnostic switch be-
ing off.
• When there is no DTC output, -12+ is outputted in
normal DTC code.
• After indicating 3 times pear 1 DTC, shift is con-
ducted to the next DTC. (After making a round, the
indications are repeated again.)
• In case of the same diagnostic code, it is used 1
DTC (3 times indication.)
Legend
A. Right-hand drive
C. Terminal assignment of diagnosis connector
B. Left-hand drive
N6A1665E
NO
TERMINAL NAME
6
DIAG CONTROL
7
CHECKER SIG
4, 5
CHECKER GND
N6A1666E
6E-154 EMISSION AND ELECTRICAL DIAGNOSIS
Example Diagnosis Trouble Code Output
Flashing of Indicator Lamp
Legend
1. (For example) In case of indicate two digits figure
“DTC22”
2. Figure of ten
3. Figure of one
Legend
A. Right-hand drive
C. Terminal assignment of diagnosis connector
B. Left-hand drive
N6A1299E
N6A1667E
EMISSION AND ELECTRICAL DIAGNOSIS 6E-155
Diagnosis Trouble Code (DTC) List
DTC#
TECH 2 STRING
21
Rack Sensor Circuit Low Voltage
22
Rack Sensor Circuit High Voltage
13
Engine Coolant Temperature (ECT) Sensor Circuit High Voltage
14
ECT Sensor Circuit Low Voltage
31
Exhaust Gas Recirculation (EGR) Vacuum Switching Valve (VSV) Solenoid Circuit Low Voltage
32
EGR VSV Solenoid Circuit High Voltage
52
Electronically Erasable Programmable Read Only Memory (EEPROM) Error
Error Classified
Trouble
Code
Diagnostic Condition
Return
Condition
Back Up
Judging
Time
Normal
12
No other trouble code.
No history of this diagno-
sis recorded
—
Rack
Sensor
Harness Open
GND short
21
Rack Voltage 0.3V or
lower, Engine speed
600 — 900rpm, and
water Temp. 0
°C
(32
°F) or higher are
detected for 3 seconds
running.
When
forward
normal
VSV: EGR
Output stop.
Rack Learning valve: 0
3.52 sec
+5V short
Rack Sensor
Power Voltage
22
5V or higher Rack Volt-
age detected.
0.52 sec
Water
Temp
Sensor
Harness Open
+B short
13
-79
°C/-110°F (390kΩ)
or lower, or 120
°C/
248
°F (115kΩ) or
higher detected.
When
forward
normal
VSV: EGR
Output stop.
0.52 sec
GND short
14
VSV:
EGR
Harness Open
GND short
*31
Output TR Monitor
When
forward
normal
VSV: EGR
Output stop.
1.57 sec
+B short
*32
ECM
EEPROM
error
52
Check when ECM is
started and when Trou-
ble Code is written.
When
forward
normal
Trouble Code other than
52 (EEPROM error) not
indicated.
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