light ISUZU TROOPER 1995 Workshop Manual

DRIVEABILITY AND EMISSIONS 6E2-131
CHART C-2C
IDLE AIR CONTROL (lAC) SYSTEM CHECK
CD • IGNITION "OFF", CONNECT IDLE AIR CONTROL (lAC) DRIVER* TO lAC VALVE. • SET PARKING BRAKE, BLOCK WHEELS, AIR CONDITIONING "OFF".
• IDLE ENGINE IN PARK (A/T) OR NEUTRAL (MIT). • INSTALL "SCAN TOOL" AND DISPLAY REVOLUTION PER MINUTE (RPM). • WITH lAC DRIVER, EXTEND AND RETRACT lAC VALVE. • ENGINE SPEED SHOULD DECREASE AND INCREASE AS lAC IS CYCLED.
I
1 I • RPM CHANGES I NO RPM CHANGE I
I I • RPM SHOULD CHANGE SMOOTHLY
WITH EACH • CHECK lAC PASSAGES.
I FLASH OF THE lAC DRIVER LIGHT FROM 700 RPM • IF OK, REPLACE lAC.
TO ABOUT 1500 RPM. DOES IT?
I
~ cf
• INSTALL APPROPRIATE lAC NODE LIGHT* IN • CHECK lAC PASSAGES.
l ENGINE CONTROL MODULE HARNESS. • IF OK, REPLACE lAC. ®
• CYCLE lAC
DRIVER AND NODE LIGHTS.
• BOTH LIGHTS SHOULD CYCLE RED AND GREEN BUT NEVER "OFF" AS RPM IS CHANGED OVER
ITS RANGE. DO THEY?
I
cf ~ IF CIRCUIT(S) DID NOT TEST GREEN AND RED, CHECK •
USING THE OTHER CONNECTOR ON THE lAC
FOR: DRIVER
PIGTAIL, CHECK RESISTANCE
•
FAULTY CONNECTOR TERMINAL CONTACTS. ACROSS
lAC COILS.
• OPEN CIRCUITS INCLUDING CONNECTIONS. •
SHOULD BE 40 TO 80 OHMS BETWEEN lAC
• CIRCUITS SHORTED TO GROUND OR VOLTAGE. TERMINALS "A" TO "B" AND "C" TO "D".
• FAULTY ENGINE CONTROL MODULE CONNECTION I OR ENGINE CONTROL MODULE.
~
l REPAIR AS NECESSARY AND RETEST. l NOT OK I .
_l
• CHECK RESISTANCE BETWEEN lAC I REPLACE lAC VALVE I TERMINALS "B" AND "C" AND "A" AND RETEST. AND "D". • SHOULD BE INFINITE.
I
~
l
I NOT OK I
]
AC DRIVER AND NODE LIGHT REQUIRED. * I J lAC VALVE AND CIRCUIT OK. I REPLACE lAC VALVE J 37027 FROM KENT-MOORE, INC. REFER TO "DIAGNOSTIC AIDS" ON AND RETEST. FACING~
~ CLEAR DIAGNOSTIC TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL "CHECK ENGINE" MALFUNCTION
INDICATOR LAMP OPERATION.
------

DRIVEABILITV AND EMISSIONS 6E2-133
CHART C-20
INDUCTION AIR CONTROL PLATE SYSTEM CHECK
AIR CONTROL SOLENOID.
• CONNECT VACUUM
GAGE TO HOSE.
• WITH ENGINE IDLING, VACUUM SHOULD BE AT LEAST 10" VACUUM.
~
I NOT OK I
I • CONNECT VACUUM PUMP WITH GAGE TO REPAIR VACUUM SOURCE I ENGINE MANIFOLD SIDE OF SOLENOID.
• IGNITION "ON", ENGINE "OFF".
• APPLY VACUUM AND OBSERVE VACUUM ACTUATOR LINKAGE.
• LINKAGE SHOULD NOT MOVE. DOES IT?
~ ~ • IGNITION "ON" ENGINE "OFF". • DISCONNECT SOLENOID ELECTRICAL ® • GROUND DIAGNOSTIC TEST TERMINAL (JUMPER CONNECTOR. DATA LINK CONNECTOR 1 TO 3). • REPEAT TEST. • APPLY VACUUM AGAIN WHILE OBSERVING • LINKAGE SHOULD MOVE. DOES IT?
LINKAGE.
L • LINKAGE SHOULD NOT MOVE.
~ ~ I MOVED I DID NOT MOVE I
I WHT /BLU SHORTED TO I FAULTY VACUUM SWITCH I GROUND VALVE
NO PROBLEM FOUND. OR SECONDARY INTAKE AIR FAUL TV ENGINE SYSTEM OK. CONTROL
MODULE (ECM)
• DISCONNECT SOLENOID ELECTRICAL
CONNECTOR.
• IGNITION
"ON", ENGINE "OFF".
• DIAGNOSTIC TEST TERMINAL GROUNDED. • CONNECT A TEST LIGHT ACROSS HARNESS
TERMINALS.
I LIGHT "ON" I LIGHT "OFF" I
I FAULTY
I
PROBE IGNITION FEED BLKIYEL WIRE WITH A SOLENOID TEST LIGHT CONNECTED TO GROUND.
I
l
LIGHT "ON" I LIGHT "OFF" j
I WHT/BLU WIRE IS OPEN, REPAIR OPEN IN BATTERY OR POSITIVE VOLTAGE FAUL TV CONNECTOR AT (BLKIYEL WIRE) CIRCUIT. ECM OR FAULTY ECM

DRIVEABILITV AND EMISSIONS 6E2-137
CHART C-3
EVAPORATIVE EMISSION CANISTER PURGE VALVE CHECK
Q) • IGNITION "OFF"
• IGNITION "ON" ENGINE STOPPED. (DO NOT CRANK ENGINE BEFORE FOLLOWING STEPS BELOW).
• DISCONNECT THROTTLE BODY TO EVAPORATE EMISSION CANISTER PURGE SOLENOID VACUUM
HOSE FROM SOLENOID.
•
APPLY VACUUM (10" HYDRAGYRUM OR 34 kPa) TO SOLENOID.
SOLENOID SHOULD HOLD VACUUM. DOES IT?
~ $
• GROUND DIAGNOSTIC TEST TERMINAL. @ • DISCONNECT SOLENOID ELECTRICAL CONNECTOR. ® • VACUUM SHOULD DROP. • APPLY VACUUM TO
SOLENOID AS IN STEP 1. DOES IT? SOLENOID
SHOULD HOLD VACUUM. DOES IT?
I
$ $ $ $
• INSTALL VACUUM GAUGE • DISCONNECT SOLENOID CHECK FOR SHORT TO I FAULTY SOLENOID. J TO HOSE PREVIOUSLY ELECTRICAL CONNECTOR. BROUND IN WHT
/RED DISCONNECTED FROM
• CONNECT TEST LIGHT WIRE. IF CIRCUIT IS SOLENOID. BETWEEN HARNESS
OK,
ENGINE CONTROL
• START ENGINE. TERMINALS. TEST LIGHT MODULE IS FAULTY. •
STABILIZE ENGINE SPEED AT SHOULD LIGHT. DOES IT?
ABOUT 2500.
• MOMENTARILY SNAP
THROTTLE OPEN AND LET
$
RETURN TO IDLE.
~
VERIFY THAT ABOUT 10" HYDRAGYRUM (34 kPa) OF VACUUM IS AVAILABLE AT FAULTY PURGE I PROBE EACH HARNESS
EVAPORATE EMISSION
SOLENOID. TERMINAL WITH A TEST
CANISTER PURGE SOLENOID, LIGHT TO GROUND.
IS IT?
I I
$
$
LIGHT "ON" ONE LIGHT
"ON" BOTH I NO LIGHT J
I I
OPEN WHT/RED REPAIR SHORT I OPEN BLK/ I NO SEE "DIAGNOSTIC
WIRE OR TO VOLTAGE IN VEL PROBLEM ~~.ON FACING FAULTY ENGINE WHT/RED WIRE.
FOUND. p . CONTROL
MODULE.
CLEAR DIAGNOSTIC TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL "CHECK ENGINE" MALFUNCTION
INDICATOR LAMP OPERATION.

6E2-148 DRIVEABILITY AND EMISSIONS
CHART C-5
KNOCK SENSOR (KS) SYSTEM CHECK
(ENGINE KNOCK, POOR PERFORMANCE, OR POOR ECONOMY)
Circuit Description:
Knock Sensor (KS) is accomplished with a module that sends a voltage signal to the Engine Control Module {ECM).
As the knock sensor detects engine knock, the
voltage from the KS module to the ECM is shut "OFF" and this
signals the ECM to retard timing, if engine speed is over about 900.
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
CD If a diagnostic trouble code 43 is not set, but a KS signal is indicated while running at 1500 revolution per
minute,
listen for an internal engine noise. Under a no load condition, there should not be any detonation,
and
if knock is indicated, an internal engine problem may exist.
@ Usually a KS signal can be generated by tapping on the right exhaust manifold. This test can also be
performed at idle. Test number 1 was run at 1500 revolution per minute, to determine if a constant KS signal
was present, which would affect engine performance.
® This tests whether the KS signal is due to the sensor, a basic engine problem, or the KS module.
@ If the module ground circuit is faulty, the KS module will not function correctly. The test light should light
indicating the ground circuit is OK.
@ Contacting terminal "E" of KS module harness with a test light 12 volts, should generate a KS signal to
determine whether the knock sensor is faulty, or the KS module can't recognize a KS signal.
Diagnostic Aids:
If the KS system checks OK, but detonation is the complaint, refer to "Detonation/Spark Knock" symptom in
"Symptoms, "Section "6E2-8".
/ I
'
TWO-WAY CONNECTOR BLACK AT REAR OF INTAKE
I
-WHT
BLK!YEL
LOCATED REAR OF 0 INTAKE PLENUM
1------LT GRN/YEL
KNOCK
SENSOR
MODULE
BLK!YEL
GROUND
TOECM~ TERMINAL ENGINE A12 GROUND
0 LOCATEDAT _ DRIVER'S SIDE REAR OF CYLINDER HEAD
Fig. 6E2-91
RED/GRN
+ TO MAIN RELAY
ENGINE CONTROL
MODULE(ECM)
KNOCK SENSOR
SIGNAL INPUT
..

DRIVEABILITV AND EMISSIONS 6E2-149
CHART C-5
KNOCK SENSOR (KS) SYSTEM CHECK
(ENGINE KNOCK, POOR PERFORMANCE, OR POOR ECONOMY)
THIS CHART SHOULD BE USED AFTER ALL OTHER CAUSES OF SPARK KNOCK HAVE BEEN CHECKED. I.E. TIMING, EXHAUST GAS RECIRCULATION, ENGINE TEMPERATURE OR EXCESSIVE ENGINE NOISE, ETC. IF DIAGNOSTIC TROUBLE CODE (DTC) 431S SET, USE THAT CHART FIRST.
• ENGINE RUNNING AT ABOVE 1500 REVOLUTION PER MINUTE. • IS THERE A KS SIGNAL INDICATED?
$ $
• ENGINE RUNNING ABOVE 1500 REVOLUTION PER @ • DISCONNECT KS. MINUTE. • REPEAT TEST. • TAP ENGINE BLOCK IN AREA OF KS. • IS THERE A KS SIGNAL INDICATED? • DOES ~scAN TOOL" INDICATE A KS SIGNAL I WHILE TAPPING ON ENGINE?
$ $
CHECK FOR ROUTING OF WIRE FROM INTERNAL KNOCK SENSOR TO KS MODULE FOR ENGINE KNOCK PICKING UP FALSE KS SIGNALS FROM OR AN ADJACENT WIRE. REROUTE AS FAUL TV SENSOR. NECESSARY. IF ROUTING IS CORRECT, REPLACE KS MODULE.
l4J $
• DISCONNECT KS MODULE. KS SYSTEM OK. • PROBE HARNESS TERMINAL "D" WITH REVIEW "DI~TIC AIDS" A TEST LIGHT TO 12 VOLTS. ON FACING .
I LIGHT "ON" I LIGHT "OFF" I
I • RECONNECT KS MODULE. REPAIR OPEN GROUND TERMINAL "D" J • DISCONNECT KS.
@
• ENGINE IDLING. • MOMENTARILY TOUCH KNOCK SENSOR HARNESS TERMINAL "A" WITH A TEST LIGHT TO 12 VOLTS. • EACH TIME THE TEST LIGHT CONTACTS TERMINAL ~A", A KS SIGNAL SHOULD BE GENERATED. • IS A KS SIGNAL INDICATED WITH "SCAN TOOL"?
$ $
FAULTY CONNECTION AT SENSOR TERMINAL "A" OPEN, SHORTED TO GROUND, OR FAULTY CONNECTION AT KS MODULE, FAULTY KS .. OR FAUL TV KS MODULE.

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

DRIVEABILITY AND EMISSIONS 6E2-159
CHART C-8
MANUAL TRANSMISSION (,MfT) SHIFT LIGHT CHECK
• IGNITION "ON", ENGINE "OFF".
• TRANSMISSION IN NEUTRAL. • NOTE: SHIFT LIGHT SHOULD "OFF".
•
DRIVE VEHICLE
LIGHT SHOULD COME "ON" DOES IT?
• IGNITION
"ON" ENGINE "OFF".
• TRANSMISSION IN GEAR • ENGINE CONTROL MODULE TERMINAL "A4" TO GROUND.
• SHIFT LIGHT "ON".
DOES
IT?

DRIVEABILITV AND EMISSIONS 6E2-161
SECTION C-1 0
AIR CONDITIONING (A/C) COMPRESSOR CLUTCH CONTROL
SYSTEM
CONTENTS
General Description ..................... 6E2-161 On-Vehicle Service ...................... 6E2-161
Operation ........................... 6E2-161 Chart C-10 Air Conditioning (A/C) System
Diagnosis ............................. 6E2-161 Functional Check ...................... 6E2-162
GENERAL DESCRIPTION
OPERATION
This system consists of a high pressure cut-out switch,
Air Conditioning (A/C) compressor
relay, A/C thermo
switch relay, A/C controller and the compressor.
The high pressure cut-out switch
(normally closed),
opens when the head pressure gets too high. This will
disable
the A/C clutch, before damage can occur to the
compressor or other
A/C components.
When
A/C control switch is "ON" and the high pressure
switch and thermo switch are
closed, a request signal
is sent to the Engine Control Module (ECM). The ECM
will then energize the A/C clutch through the A/C
clutch relay. The A/C controller which is separate from
the ECM will then turn the A/C cooling fan "ON".
The A/C controller controls the A/C cooling fan, as well
as sending a signal to the ECM on model equipped with
automatic transmission.
The
ECM will disable the A/C clutch during Wide Open
Throttle,
or high power steering loads. The ECM has a
slight delay for clutch engagement to allow for the idle
to slightly increase. Refer to CHART C-1 0 for wiring and
circuit description.
DIAGNOSIS
Chart C-10 should be used for the electrical portion of
the A/C circuit. Section 1 B should be used for
diagnosing the refrigerant portion of the system. The
"Scan tool" will be used in diagnosing the system, as it
has the ability to read the A/C request inputto the ECM,
as well as displaying when the ECM has commanded
the
A/C clutch "ON".
ON-VEHICLE SERVICE
For removal and replacement of A/C components,
refer to
A/C (SECTION 1 B) in this Manual.

DRIVEABILITV AND EMISSIONS 6E2-163
CHART C-10
AIR CONDITIONING (A/C) SYSTEM FUNCTIONAL CHECK
IGNITION "ON" ENGINE RUNNING.
CYCLE AIR CONDITIONING (A/C) SWITCH "ON" AND "OFF". A/C COMPRESSOR CLUTCH SHOULD
CYCLE "ON" AND "OFF"
DOES IT?
$
$
"SCAN TOOL" INSTALLED.
NO PROBLEM FOUND, REFER TO)>e€TIO'N REQUEST A/C "1B", AIR CONDITIONING"
"SCAN TOOL" SHOULD DISPLAY "YES" FOR FOR SERVICE OF A/C SYSTEM A/C REQUEST AND "ON" FOR A/C CLUTCH.
DOES IT?
$
$
IGNITION "ON", ENGINE "OFF". USING TEST BASIC A/C PROBLEM. REFER TO~ LIGHT, BACK PROBE ENGINE CONTROL MODULE "1B", AIR CONDITIONING"
TERMINAL C9 WITH A/C REQUESTED. LIGHT
SHOULD BE "ON". IS IT?
$ $
USING TEST LIGHT CONNECTED TO BATTERY IGNITION "OFF". REMOVE A/C THERMO
POSITIVE VOLTAGE, BACK PROBE ENGINE RELAY. IGNITION "ON" A/C REQUESTED, CONTROL MODULE TERMINAL PROBE THE GRN/WHT WIRE OF RELAY. "A2". LIGHT SHOULD BE "ON". LIGHT SHOULD BE "ON" IS IT?
IS IT?
I
$ $
~ $ OPEN IN PNK/GRN WIRE I OPEN IN GRN/WHTJ OPEN GRN WIRE
OPEN GRY/YEL WIRE OR WIRE. OR OR FAULTY A/C THERMO SWITCH FAULTY FAULTY A/C CLUTCH RELAY. OR COMPRESSOR RELAY. FAULTY THERMO SWITCH RELAY.
CLEAR DIAGNOSTIC TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NO "CHECK ENGINE" MALFUNCTION INDICATOR LAMP.