1995 ISUZU TROOPER Workshop Manual

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.

6E2-162 DRIVEABILITY AND EMISSIONS
CHART C-10
AIR CONDITIONING (A/C) SYSTEM FUNCTIONAL CHECK
Circuit Description:
When the Air Conditioning (A/C) diagnostic test mode is selected, the Engine Control Module (ECM) will supply a
ground to the
A/C clutch relay. Battery positive voltage is then supplied to the A/C clutch through the completing
of circuit through the thermo switch relay, which is part of the A/C "ON/OFF" switch circuit. If the A/C system
exhibits high pressure or
an overheating condition exist, the A/C system will be disabled by the open of the A/C
high pressure switch or the A/C thermo switch.
Diagnostic Aids:
The A/C high pressure switch is located in the high pressure side A/C hose.
The
thermo cut-out switch is part of the A/C evaporator mounted under the dash. For further information about
the
A/C system, refer to A/C (SECTION 1 8).
BRN
TONC FUSE
NC HIGH
PRESSURE SWITCH
(LOCATED IN
RECEIVER/DRYER)
LTGRN
BRN
NC Switch
NC DIODE
BRN a GRY!YEL
THERMO CUT­OUT RELAY
LTGRN PNK/ GRN
NCCOMP CLUTH RELAY
PARTOF1-­FAN I SWITCH I I CIRCUIT I __ I
BLK THERMO CUT-OUT MODULE j_
Fig. 6E2-100
ENGINE
CONTROL
MODULE (ECM)
NC COMPRESSOR CLUTCH RELAY DRIVER OUTPUT
NC REQUEST INPUT

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.

6E2 164 DRIVEABILITY AND EMISSIONS
SECTION C-13
POSITIVE CRANKCASE VENTILATION (PCV)
CONTENTS
GENERAL DESCRIPTION ................. 6E2-164 DIAGNOSIS ............................ 6E2-165
PCVValve .......................... 6E2-164 Functional Check of PCV ................ 6E2-165
Results of Incorrect Operation ............ 6E2-165
ON-VEHICLE SERVICE .................... 6E2-165
GENERAL DESCRIPTION
PCV VALVE
A Positive Crankcase Ventilation (PCV) system is used
to consume crankcase vapors in the combustion
process instead
of venting to atmosphere. Fresh air
from the throttle body is supplied to the crankcase,
mixed
with blow-by gases and then passed through a
Positive Crankcase Ventilation (PCV) into the intake
manifold.
The primary control is through the PCV (Fig. 6E2-101)
which meters the
flow at a rate depending on manifold
vacuum.
Fig.
6E2-101
To maintain idle quality, the PCV restricts the flow
when intake manifold vacuum is high. If abnormal
operating conditions arise, the system is designed to
allow excessive amounts of blow-by gases to back
flow through the crankcase vent tube into the air
cleaner to be consumed by normal combustion.
A
leaking valve or hose would cause:
• Rough idle.
• Stalling.
•
High idle speed.
..

DRIVEABILITV AND EMISSIONS 6E2-165
DIAGNOSIS
FUNCTIONAL CHECK OF POSITIVE
CRANKCASE VENTILATION (PCV)
If an engine is idling rough, check for a clogged PCV or
plugged hose. Replace as required. Use the following
procedure.
1. Remove PCV from rocker arm cover.
2. Run the engine at idle.
3. If there is no vacuum at valve, check for plugged
hoses or manifold port, or PCV.
Replace plugged or deteriorated hoses.
4. Stop the engine and remove PCV. Remove
PCV hose. Inspect metered orifice for being
restricted or
plugged. If restricted clean orifice.
With this system, any
blow-by in excess of the system
capacity (from a
badly-worn engine, sustained heavy
load, etc.) is exhausted into the intake manifold and is
drawn into the engine. Proper
operation
of the PCV System is dependent
upon a
sealed engine. If oil sledging or dilution is
noted, and the PCV System is functioning properly,
malfunction
indicator lamp for possible cause and
correct to ensure that system
will function as intended.
RESULTS OF INCORRECT OPERATION
A plugged valve or hose may cause:
• Rough idle.
• Stalling
or slow idle speed.
• Oil leaks.
• Oil
in air cleaner.
• Sludge
in engine.
ON-VEHICLE SERVICE
An engine which is operated without any crankcase
ventilation can be damaged. Periodically, inspect the
PCV, hoses
and clamps and replace any showing
signs
of deterioration.

6E2-166 DRIVEABILITY AND EMISSIONS
SPECIAL TOOLS
ILLUSTRATION TOOL NO.
TOOL NAME ILLUSTRATION
~
J-23738-A
Vacuum pump with gage
~
J-35616-A
Connector test adapter kit
'
J-35689-A
Metri-pack terminal remover
~
J-33095
Engine control module
connector terminal remover
$
J-34730-2A
Injector test light
•
J-34730-B
Multipart fuel injection
diagnostic kit
~~~ J-37027A
~~~
Idle air control system driver
TOOL NO.
TOOL NAME
J-34142-B
Unpowered test light
J-34636
Circuit tester
J-28742-A
Weather pack terminal
remover
J-26792
Spark tester
J-34730-3
Injector tester
J-39185
Intake manifold plate
J-39200
High impedance multimeter
..