Isuzu N-Series. Manual - part 450

6E-136 EMISSION AND ELECTRICAL DIAGNOSIS

Working Check

Apply powervoltage between the terminals, there
is no problem if the negative pressure does not rise
when applied to the input port.

Caution:
When measuring resistance with a circuit tester, be
careful not to damage or deform the terminals.

N6A1266E

EMISSION AND ELECTRICAL DIAGNOSIS 6E-137

Aneroid Compensator Malfunction

N6A1267E

6E-138 EMISSION AND ELECTRICAL DIAGNOSIS

Inspection

1. Thermosensor (Engine coolant temperature

(ECT))
Soak the temperature sensitive part of a ther-
mosensor in the water, and while changing the wa-
ter temperature, make sure the resistance is
changed as the following graph shows:

2. Vacuum Switching Valve (VSV)

Resistance Check

Check the resistance between the VSV connector
terminals using a circuit tester.
Cold Resistance
: 37 — 44 (

Ω) (for 12 Volt)

: 159 — 169 (

Ω) (for 24 Volt)

Connect battery voltage between VSV connector
terminals and make sure of the continuity between
the pots.

Airtight Check

Apply negative pressure to the negative pressure
input port as illustrated on the left. 
Although there is leakage, it is no problem if the
negative pressure rises to -46.7 kPa (-350 mmHg /
-6.77 psi) or more.

Legend

1. Resistance (k

Ω)

2. ECT 

°F (°C)

N6A1254E

N6A1255E

Legend

1. 2 Pin
2. Port

N6A1264E

N6A1265E

EMISSION AND ELECTRICAL DIAGNOSIS 6E-139

Working Check

Apply powervoltage between the terminals, there
is no problem if the negative pressure does not rise
when applied to the input port.

Caution:
When measuring resistance with a circuit tester, be
careful not to damage or deform the terminals.

3. Actuator

Diaphragm is built in the actuator, by which the in-
side of the actuator is divided into two, atmospheric
room and negative pressure room.

4. Aneroid compensator Actuator

The link of the actuator for the aneroid compensa-
tor is connected to full load set lever. 

The full load set lever is connected to a U-lever. 
When the atmospheric sensor built in Engine Con-
trol Module (ECM) makes the actuator work, the
full load set lever and U-lever are rotated to a spec-
ified position so that the control rack is drawn in the
direction of reducing fuel injection amount.

Legend

1. Vacuum chamber
2. Atmospheric chamber
3. Diaphragm

N6A1266E

N6A1273E

Legend

1. Aneroid compensator actuator
2. Full load set lever

N6A1274E