Isuzu N-Series. Manual - part 421

6E-20 EMISSION AND ELECTRICAL DIAGNOSIS

• The following table shows, which functions are

used the available equipment versions.

N6A1131E

N6A1132E

N6A1133E

N6A1134E

EMISSION AND ELECTRICAL DIAGNOSIS 6E-21

Typical Scan Data Values

Use the Typical Scan Data Values Table only after the
On-Board Diagnostic System Check has been complet-
ed, no diagnostic trouble codes were noted, and you
have determined that the on-board diagnostics are func-
tioning properly. Scan tool values from a properly-run-
ning engine may be used for comparison with the engine
you are diagnosing. The typical scan data values repre-
sent values that would be seen on a normally-running
engine.

Notice:
A scan tool that displays faulty data should not be used,
and the problem should be reported to the scan tool

manufacturer. Use of a faulty scan tool can result in mis-
diagnosis and unnecessary replacement of parts.

Only the parameters listed below are referred to in this
service manual for use in diagnosis. For further informa-
tion on using the scan tool to diagnose the engine con-
trol module and related sensors, refer to the applicable
reference section listed below. If all values are within the
typical range described below, refer to the symptoms
section for diagnosis.

Test Conditions

Engine running, lower radiator hose hot, transmission in
park or neutral, closed loop, accessories off, brake not
applied and air conditioning off.

Data List (Typical Data)

Troubleshooting

Caution taken in inspecting

1. In inspecting system, write down self-diagnosis

code to be indicated. (especially, when plural self-
diagnosis codes are indicated.)

2. Before eliminating the indicated self-diagnosis

codes by a memory clear switch, doubly inspect
abnormal place as indicated in self-diagnosis
code. (Self-diagnosis code means ‘Warning.’ Make
sure to inspect abnormal section.)

TECH 2 STRING

TYPICAL DATA VALUES (IDLE)

Ignition Switch 

(On/Off)

On

Starter Switch 

(On/Off)

Off

Exhaust Break Switch 

(On/Off)

Off

Transmission Gear Position Switch

N.2.3.4.5.6

Transmission Spec. Select Switch 

(AT/MT)

Automatic Trans

Engine Spec. Select Switch 

(S/N)

S/N

IAT Switch 

(Yes/No and High/Low)

High

EGR/VSS System 

(Yes/No)

Yes

Rack Sensor Voltage 

(V)

1

Engine Coolant Temperature Sensor 
Voltage 

(V)

1.7 —1.9

Engine Coolant Temperature 

°F(°C)

176 (80)

Engine Speed 

(rpm)

800

Barometric Voltage 

(V)

2.9

Barometric Pressure 

(mmHg)

761

6E-22 EMISSION AND ELECTRICAL DIAGNOSIS

Inspection Procedure Flowchart

N6A1135E

EMISSION AND ELECTRICAL DIAGNOSIS 6E-23

Notice:
Please note that some items of self-diagnosis code may
not be generated unless the engine is warmed up or un-
less the vehicle is driven under load.

Self-diagnosis Functions

Memorization of self-diagnosis 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 self-diag-
nosis code will remain in memory. (The memory will be
eliminated only by a memory clear switch.)

Elimination of self-diagnosis code
The self-diagnosis code memorized in the EEPROM
with in the ECM can be eliminated only by Scan Tool or
the operation of the memory clear switch.
The elimination method memory clear switch will be de-
scribed below:

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 (DATA LINK CONNECTOR)

Legend

A. Right-hand drive

C. Terminal assignment of data link connector (DLC)

B. Left-hand drive

N6A1665E