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
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