1995 ISUZU TROOPER Workshop Manual

DRIVEABILITV AND EMISSIONS 6E2-153
DIAGNOSIS
Diagnosis of the Exhaust Gas Recirculation (EGR)
system is covered in CHART C-7 at the end of this
section.
ON-VEHICLE SERVICE
EXHAUST GAS RECIRCULATION (EGR)
MANIFOLD PASSAGE
[!j INSPECTION AND REPAIR
If Exhaust Gas Recirculation (EGR) passages in the inlet
manifold indicate excessive build-up
of deposits, the
passages should
be cleaned. Care should be taken to
ensure that
all loose particles are completely removed,
to prevent them
from clogging the EGR valve, or from
being ingested into the engine.
Do not wash EGR valve in solvents or de greaser as
permanent damage to valve diaphragm may result.
Also, sand blasting
of the valve is not recommended,
since this can affect the operation
of the valve.
EXHAUST GAS RECIRCULATION (EGR)
VALVE REPLACEMENT
1••1 REMOVAL
1. Air cleaner duct assembly.
2. Vacuum hoses from EGR valve.
3. EGR pipe
4. Retaining bolts (2) from valve.
5. EGR valve & gasket.
1••1 INSTALLATION
5. EGR valve & New gasket.
4. Retaining bolts to valve.
3. EGR pipe.
2. Vacuum hoses to EGR valve.
1. Air cleaner dust assembly.
EXHAUST GAS RECIRCULATION (EGR)
BACKPRESSURE TRANSDUCER (BPT)
REPLACEMENT
1••1 REMOVAL
1. Vacuum hoses.
2. Back pressure transducer
1••1 INSTALLATION
1. Vacuum hoses
2. Back pressure transducer
EXHAUST GAS RECIRCULATION (EGR)
VACUUM SWITCH VALVE (VSV)
REPLACEMENT
1••1 REMOVAL
1. Electrical connector
2. Vacuum hoses from Vacuum Switch Valve (VSV)
3. Two fasteners hold VSV to intake manifold.
1••1 INSTALLATION
3. VSV and Retaining bolts.
2. Vacuum hoses
1. Electrical connector

6E2-154 DRIVEABILITY AND EMISSIONS
CHART C-7A
EXHAUST GAS RECIRCULATION (EGR) SYSTEM CHECK
Circuit Description:
A properly operating Exhaust Gas Recirculation (EGR) system will directly affect the air/fuel requirements of the
engine. Since the exhaust gas introduced into the air/fuel mixture is
an inert gas (contains very little or no oxygen),
less fuel is required
to maintain a correct air/fuel ratio. If the EGR system were to become inoperative, the inert
exhaust gas
would be replaced with air and the air/fuel mixture would be leaner. The Engine Control Module
(ECM) would compensate for the lean condition by adding fuel, resulting in higher block learn values.
The engine control system operates within
two block learn cells, a closed throttle cell and an open throttle cell.
Since EGR is not used at idle, the closed throttle cell would not be affected by EGR system operation. The open
throttle
cell is affected by EGR operation and when the EGR system is operating properly, the block learn values in
both
cells should be close to being the same. If the EGR system was inoperative, the block learn value in the open
throttle
cell would change (become higher) to compensate for the resulting lean system, but the block learn value
in the closed throttle
cell would not change.
This change or difference in block learn values is used to monitor
EGR system performance.
Diagnostic Aids:
The EGR valve chart is a check of the EGR system. If the EGR system works properly, check other items that could
result in high block learn values in the open throttle
cell, but not in the closed throttle cell.
CHECK:
EGR Passages
Restricted
or blocked
Manifold Absolute Pressure Sensor
A manifold absolute pressure sensor may shift in calibration enough to affect fuel delivery. Use CHART
C-1 0,
manifold absolute pressure output check.
EGR VALVE
EGRV
+
BACK
PRESSURE
TRANSDUCER
vsv
+ EGRVALVE VACUUM SWITCHING
VALVE (VSV)
ENGINE HARNESS
CONNECTOR
'+--+-' ( BLU)
GRN AB
t tt BL~L ---+ TO IGN
PORTED VACUUM
Fig. 6E2-98
ENGINE HARNESS
CONNECTOR
(BLU)
ENGINE CONTROL
MODULE(ECM)
EGR VALVE VSV DRIVER
•

DRIVEABILITY AND EMISSIONS 6E2-155
CHART C-7A
EXHAUST GAS RECIRCULATION (EGR) SYSTEM CHECK
• FIRMLY GRASP TOP OF EXHAUST GAS
RECIRCULATION (EGR} VALVE AND CHECK FOR LOOSENESS BY TRYING TO ROTATE VALVE IN BOTH DIRECTIONS. IS LOOSENESS FELT?
• PLACE TRANSMISSION IN "PARK" OR "NEUTRAL."
• RUN WARM ENGINE AT IDLE. • ENGINE TEMPERATURE MUST BE ABOVE so·c (176.F}. • DISCONNECT VACUUM HOSE TO EGR VALVE. • APPLY 10 INCHES OF VACUUM TO EGR VALVE. • ENGINE SHOULD RUN ROUGH AND/OR STALL.
DOES IT?
• CHECK FOR DAMAGE VACUUM HOSE FROM THROTILE BODY TO EGR VALVE. • CONNECT VACUUM GAGE TO EGR BACKPRESSURE
TRANSDUCER SIDE OF EGR VALVE. • INCREASE ENGINE SPEED ABOVE 2000 REVOLUTION PER MINUTE. SHOULD HAVE 10 INCHES OF VACUUM. DOES IT?
• ENGINE IDLING CHECK VACUUM SOURCE BEFORE EGR MODULATOR.
• REMOVE EGR VALVE AND CLEAN
ASSEMBLY.
•
REPLACE VALVE IF NECESSARY.
EGR SYSTEM WORKING PROPERLY. NO TROUBLE FOUND.
REPLACE
BACKPRESSURE TRANSDUCER.
CLEAR DIAGNOSTIC
TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL "CHECK ENGINE" MALFUNCTION
INDICATOR LAMP OPERATION.

6E2-156 DRIVEABILITY AND EMISSIONS
MEMO

DRIVEABILITY AND EMISSIONS 6E2-157
SECTION C-8
SHIFT INDICATOR LIGHT (MIT ONLY)
CONTENTS
General Description . . . . . . . . . . . . . . . . . . . . . 6E2-157 Diagnosis ............................. 6E2-157
Purpose ............................ 6E2-157 Transmission Switch Functional Check ..... 6E2-157
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 6E2-157 Clutch Switch Functional Check ........... 6E2-157
Chart C-8 Manual Transmission (M/T)
Shift Light ........................... 6E2-158
GENERAL DESCRIPTION
PURPOSE
The shift indicator light is a device which is installed in
the instrument
panel to urge the driver to up shiftatthe
proper moment. This insures operations for best fuel
economy.
OPERATION
It turns on as soon as vehicle conditions become
suitable for operation in the next higher gear, and turns
off as the clutch is released for up shift.
The engine parameters used
to activate the shift
indicator
light are engine speed, engine load and
engine
coolant temperature. The engine load is sensed
as a function of Throttle Body (TB) position by a sensor
built into the TB. The
shift indicator
light turns on when the following
conditions exist simultaneously:
1. Engine coolant temperature is hotter than -s·c.
2. TB is not in idle position.
3. The engine load, is not greater than the
predetermined
values.
4. The transmission gear is in any forward position
other then 5th, that is, either
of the two
transmission switches (1st-2nd switch and 3rd-
4th switch) is on. 1st-2nd switch turns on
when the
transmission is in 1st-2nd, and 3rd-4th switch
turns on when the transmission 3rd
or 4th.
5. The clutch is engaged (clutch switch is "ON").
The control system schematic is shown in CHART
C-8.
DIAGNOSIS
See CHART C-8.
TRANSMISSION SWITCH FUNCTIONAL
CHECK
1. Connector from the suspected faulty switch.
2. An ohmmeter across terminals of switch.
3. Operate gear shift.
4. Ohmmeter should indicate open (infinity) then
closed (00).
5. Replace switch if not operating as described.
CLUTCH SWITCH FUNCTIONAL CHECK
1. Remove clutch switch.
2. Ohmmeter to terminal of clutch switch.
3. Operate the clutch switch.
4. Ohmmeter should read "closed" (00) then
"open" (infinity) when clutch switch is pressed.
5. Replace switch if not operating as described.

6E2-158 DRIVEABILITV AND EMISSIONS
CHART C-8
MANUAL TRANSMISSION (M/T) SHIFT LIGHT CHECK
Circuit Description:
The shift light indicates the best transmission shift point for maximum fuel economy. The light is controlled by the
Engine Control Module
(ECM) and is turned "ON" by grounding the ORN/BLU wire. The ECM uses information
from the following inputs to control the shift light.
The
ECM uses information from the following inputs to control the shift light:
• Engine coolant temperature sensor
• Throttle position sensor
• Vehicle speed sensor
• Revolution per minute
The
ECM uses the measured revolution per minute and the vehicle speed to calculate what gear the vehicle is in.
It's this calculation that determines when the shift light should be turned "ON".
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
fault in the
ECM.
® This checks the shift light circuit up to the ECM connector .If the shift light illuminates, then the ECM connector
is faulty
or the ECM does not have the ability to ground the circuit.
TO
IGNITION SWITCH
t
BLU/RED GRY/BLU
•
SHIFT SWITCHES #CLOSED" IN GEAR
BLU/ORN
SHIFT SHIFT LIGHT
LIGHT
RELAY
TO
LIGHTING SWITCH
Fig. 6E2-99
ENGINE CONTROL
MODULE(ECMl
SHIFT
LIGHT
CONTROL