Isuzu N-Series. Manual - part 448

6E-128 EMISSION AND ELECTRICAL DIAGNOSIS

Inspection

1. Exhaust Brake Magnetic Valve

Inspection

Connect the magnetic valve connector terminal
No.1 and No.2 to (+) terminal and (-) terminal of
battery, respectively, and check the continuity be-
tween the ports.

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

2. Exhaust Throttle Valve

Working Check

Actuate the exhaust brake with the engine idling
and make sure that you hear the valve strike on the
stopper.

Airtight Check

Apply a negative pressure of 53.3 — 93.3 kPa (400
— 700 mmHg/7.73 — 13.54 psi) to the power
chamber by means of a vacuum pump and make
sure of the smooth opening/closing of the exhaust
brake valve.

Apply a negative pressure of 86.7 — 93.3 kPa (650
— 700 mmHg/12.57 — 13.54 psi) to the power
chamber using a vacuum pump and make sure the
average of measurements at Point A and Point B
of the clearance between valve and body is as fol-
lows: 0.4 — 0.6 mm (0.016 — 0.024 in) (Minimum:
0.4 mm/0.016 in)
If the clearance is out of this range, adjust with the
adjusting bolt.

Legend

A. Inlet (Vacuum pump)
B. Outlet (unit)

C. Exhaust (air filter)

N6A1247E

N6A1248E

Legend

1. Power chamber
2. Adjust bolt
3. Valve
4. Close

N6A1249E

N6A1250E

EMISSION AND ELECTRICAL DIAGNOSIS 6E-129

3. Intake Throttle Valve

Working Check

Disconnect the vacuum hose from the actuator and
try to move the rod by hand, making sure of the
smooth move of the rod.

4. Vacuum Switching Valve; Intake Throttle

Inspection
Connect the vacuum switching valve connector termi-
nals No.1 and No.2 to (+) terminal and (-) terminals of
battery, respectively, and check the continuity between
the ports.
If the check result is abnormal, repair or replace the
valve.

5. Accelerator Switch (2-pole connector type)

Inspection

1) Check the continuity between the switch con-

nector terminals.

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

2) Check the smooth move of the pushrod. If the

check result is abnormal, repair or replace the
push rod.

Removal

1) Accelerator Switch 
2) Disconnect the connector. 

Loosen the lock nut. 
Turn the switch to remove.

Reinstallation

To install, follow the removal procedure in reverse
order:
1) Drive the threaded part of the switch until its

end surface becomes flush with that of the
bracket side of nut.

2) Tighten the lock nut. 

Tightening torque: 1.3 N

⋅m (0.13 kg⋅m/11.5

lb

⋅in)

Legend

1. Vacuum hose

N6A1251E

N6A1252E

6E-130 EMISSION AND ELECTRICAL DIAGNOSIS

EGR System Malfunction

N6A1674E

EMISSION AND ELECTRICAL DIAGNOSIS 6E-131

Inspection

1. Thermosensor (Engine Coolant Temperature)

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. Electronic Vacuum Regulating Valve (EVRV)

(Equipped with Exhaust Gas Recirculation (EGR)
and Variable Swirl System (VSS))

Resistance Check

Check the resistance between the EVRV connec-
tor terminals using a circuit tester. 
Cold Resistance: 12

±1 (Ω)

Connect battery voltage between EVRV connector
terminals and make sure of the continuity between
the ports.

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.

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

Legend

1. Resistance (k

Ω)

2. ECT 

°F (°C)

N6A1254E

N6A1255E

Legend

1. Port
2. Pin

Legend

1. Vacuum port

N6A1256E

N6A1257E