air condition LEXUS SC400 1991 Service Repair Manual

ABBREVIATIONS USED IN THIS
MANUAL
ABS Anti±Lock Brake System J/B Junction Block
A/C Air Conditioner LED Light Emitting Diode
ALR Automatic Locking Retractor LH Left±Hand
APPROX. Approximation LHD Left±Hand Drive
A/T, ATM Automatic Transmission LLC Long Life Coolant (Year Around Coolant)
ATF Automatic Transmission Fluid Max. Maximum
BTDC Before Top Dead Center Min. Minimum
BVSV Bimetal Vacuum Switching Valve MP Multipurpose
CALIF. Vehicles Sold in California N Neutral
CB Circuit Breaker OD, O/D Overdrive
DOHC Double Over Head Cam O/S Oversize
DP Dash Pot P & BV Proportioning and Bypass Valve
ECT Electronic Controlled Transmission PCV Positive Crankcase Ventilation
ECU Electronic Controlled Unit PS Power Steering
EFI Electronic Fuel Injection RH Right±Hand
EGR Exhaust Gas Recirculation RL Rear Left
ELR Emergency Locking Retractor RR Rear Right
EPR Evaporator Pressure Regulator RR, Rr Rear
ESA Electronic Spark Advance SRS Supplemental Restraint System
EVAP Evaporative (Emission Control) SSM Special Service Materials
EX Exhaust (manifold, valve) SST Special Service Tools
Ex. Except STD Standard
FIPG Formed in Place Gasket SW Switch
FL Front Left TDC Top Dead Center
FL Fusible Link TDCL Total Diagnostic Communication Link
FPU Fuel Pressure Up Temp. Temperature
FR Front Right TRAC Traction Control System
FR, Fr Front TWC Three±Way Catalyst
HAC High Altitude Compensation VSV Vacuum Switching Valve
IG Ignition VTV Vacuum Transmitting Valve
IN Intake (manifold, valve) w/ With
INT Intermittent w/o Without
ISC Idle Speed Control
IN±34±
INTRODUCTION Abbreviations Used in This Manual
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HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
A large number of ECU controlled systems are used in the LEXUS SC400. In \
general, the ECU controlled sys-
tem is considered to be a very intricate system requiring a high level o\
f technical knowledge and expert skill to
troubleshoot. However, the fact is that if you proceed to inspect the circuits one by one, trou\
bleshooting of these
systems is not complex. If you have adequate understanding of the system\
and a basic knowledge of electricity,
accurate diagnosis and necessary repair can be performed to locate and fix the p\
roblem. This manual is de-
signed through emphasis of the above standpoint to help service technici\
ans perform accurate and effective
troubleshooting, and is compiled for the following major ECU controlled \
systems:
Repair ManualSystemPage
1. EngineTR±1
Vl1
2. Automatic TransmissionAT±33
Vol. 13. Anti±Lock BrakeBR±43
4. Traction ControlBR±139
5. Steering Column Electronic ControlSR±22
6. SRS AirbagAB±25
7. Power Seat ControlBE±265
Vl2
8. Door Lock ControlBE±347
Vol. 29. Theft DeterrentBE±381
10. Wireless Door Lock ControlBE±425
11. Cruise ControlBE±459
12. Air ConditionerAC±21
The troubleshooting procedure and how to make use of it are described on\
the following pages.
±
INTRODUCTION How to Troubleshoot ECU Controlled SystemsIN±15
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HOW TO PROCEED WITH TROUBLESHOOTING
Carry out troubleshooting in accordance with the procedure on the follow\
ing page. Here, only the basic proce-
dure is shown. Details are provided in each section, showing the most effective methods for each circuit. Confirm
the troubleshooting procedures first for the relevant circuit before beginn\
ing troubleshooting of that circuit.


Ask the customer about the conditions and the
environment when the problem occurred.
\b 
Confirm the symptoms and the problem
conditions, and check the diagnostic codes.
(When the problem symptoms do not appear
during confirmation, use the symptom simu-
lation method described later on.)
  
Check the result obtained in Step \b, then
confirm the inspection procedure for the sys-
tem or the part which should be checked us-
ing the diagnostic code chart or the matrix
chart of problem symptoms.

Check and repair the affected system or part
in accordance with the instructions in Step .

After completing repairs, confirm that the
problem has been eliminated.
(If the problem is not reproduced, perform the
confirmation test under the same conditions
and in the same environment as when it oc-
curred for the first time.)
IN±16
±
INTRODUCTION How to Troubleshoot ECU Controlled Systems
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[1] CUSTOMER PROBLEM ANALYSIS
In troubleshooting, the problem symptoms must be confirmed accurately and \
all preconceptions must be
cleared away in order to give an accurate judgment. To ascertain just what the problem symptoms are, it is ex-
tremely important to ask the customer about the problem and the conditions at t\
he time it occurred.
Important Points in the Problem Analysis
The following 5 items are important points in the problem analysis. Past pr\
oblems which are thought to be unre-
lated and the repair history, etc. may also help in some cases, so as much information as possible s\
hould be
gathered and its relationship with the problem symptoms should be correctly asce\
rtained for reference in trou-
bleshooting. A customer problem analysis table is provided in the troubl\
eshooting section for each system for
your use.
Important Points in the Customer Problem Analysis
wWhat Vehicle model, system name
w When Date, time, occurrence frequency
w Where Road conditions
w Under what conditions? Running conditions, driving con\
ditions, weather conditions
w How did it happen? Problem symptoms
(Sample) Engine control system check sheet.
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INTRODUCTION How to Troubleshoot ECU Controlled SystemsIN±17
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[2] SYMPTOM CONFIRMATION AND DIAGNOSTIC CODE CHECK
The diagnostic system in the LEXUS SC400 fulfills various functions. The fi\
rst function is the Diagnostic Code
Check in which a malfunction in the signal circuits to the ECU is stored\
in code in the ECU memory at the time
of occurrence, to be output by the technician during troubleshooting. Anot\
her function is the Input Signal Check
which checks if the signals from various switches are sent to the ECU correct\
ly.
The air conditioner system has an Actuator Check function whereby the ECU a\
utomatically operates the actua-
tors of the damper and blowermotor, etc. to check the operation. The cruise control system has a Cancel Si\
gnal
Check function which memorizes and displays what sort of signal it was that l\
ast cancelled the cruise control.
By using these check functions, the problem areas can be narrowed down qui\
ckly and troubleshooting can be
performed effectively. Diagnostic functions are incorporated in the following systems in the \
LEXUS SC400.
SystemDiagnostic CodeCheckInput Signal Check(Sensor Check)Other Diagnosis Function
Engine (with Test Mode)
Automatic Transmission (with Test Mode)
Anti±Lock Brake
Traction Control (Option)
SRS Airbag
Power Seat (only vehicles with memory function)
Wireless Door Lock Control
Cruise Control Cancel Signal
Check
Air Conditioner Actuator Check
In diagnostic code check, it is very important to determine whether the pr\
oblem indicated by the diagnostic code
is still occurring or occurred in the past but returned to normal at pre\
sent. In addition, it must be checked in the
problem sym ptom check whether the malfunction indicated by the diagnostic code is d\
irectly related to the prob-
lem symptom or not. For this reason, the diagnostic codes should be chec\
ked before and after the symptom
confirmation to determine the current conditions, as shown in the table below. If this is not done, it may, depend-
ing on the case, result in unnecessary troubleshooting for normally oper\
ating systems, thus making it more diffi-
cult to locate the problem, or in repairs not pertinent to the problem. Ther\
efore, always follow the procedure in
correct order and perform the diagnostic code check.
DIAGNOSTIC CODE CHECK PROCEDURE
IN±18±
INTRODUCTION How to Troubleshoot ECU Controlled Systems
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[3] SYMPTOM SIMULATION
The most difficult case in troubleshooting is when there are no problem symptoms occurring. In s\
uch cases, a
thorough customer problem analysis must be carried out, then simulate the same or similar conditions and envi-
ronment in which the problem occurred in the customer's vehicle. No matter now much experience a technician
has, or how skilled he may be, if he proceeds to troubleshoot without confir\
ming the problem symptoms he will
tend to overlook something important in the repair operation and make a wron\
g guess somewhere, which will
only lead to a standstill. For example, for a problem which only occurs when\
the engine is cold, or for a problem
which occurs due to vibration caused by the road during driving, etc., the pr\
oblem can never be determined so
long as the symptoms are confirmed with the engine hot condition or the \
vehicle at a standstill. Since vibration,
heat or water penetration (moisture) are likely causes for problems which are \
difficult to reproduce, the symptom
simulation tests introduced here are effective measures in that the external causes are applied to the vehicle
in a stopped condition.
Important Points in the Symptom Simulation Test
In the symptom simulation test, the problem symptoms should of course be co\
nfirmed, but the problem area
or parts must also be found out. To do this, narrow down the possible problem circuits according to the sym\
ptoms
before starting this test and connect a tester beforehand. After that, carry out the symptom simulation test, judg-
ing whether the circuit being tested is defective or normal and also confir\
ming the problem symptoms at the
same time. Refer to the matrix chart of problem symptoms for each system to \
narrow down the possible causes
of the symptom.
[1] VIBRATION METHOD: When vibration seems to be the major cause.
CONNECTORS
Slightly shake the connector vertically and horizon-
tally.
WIRE HARNESS
Slightly shake the wire harness vertically and horizontally.
The connector joint, fulcrum of the vibration, and body
through portion are the major areas to be checked thor-
oughly.
PARTS AND SENSORS
Apply slight vibration with a finger to the part of the
sensor considered to be the problem cause and
check if the malfunction occurs.
HINT: Applying strong vibration to relays may result
in open relays. IN±20
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INTRODUCTION How to Troubleshoot ECU Controlled Systems
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[2] HEAT METHOD: When the problem seems to occur when the suspect area is heated.
Heat the component that is the likely cause of the malfunc-
tion with a hair dryer or similar object. Check to see if the
malfunction occurs.
NOTICE:
(1) Do not heat to more than 60°C (140 °F).
(Temperature limit that no damage is done to the
component).
(2) Do not apply heat directly to parts in the ECU.
[3] WATER SPRINKLING METHOD: When the malfunction seems to occur on a
rainy\
day or in a high±humidity condition.
Sprinkle w ater onto the vehicle and check to see if the mal-
function occurs.
NOTICE:
(1) Never sprinkle water directly into the engine compartment, but indirectly change the tempera-
ture and humidity by applying water spray onto
the radiator front surface.
(2) Never apply water directly onto the electronic components.
(Service hint)
If a vehicle is subject to water leakage, the leaked water
may contaminate the ECU. When testing a vehicle with a
water leakage problem, special caution must be used.
[4] OTHER: When the malfunction seems to occur when electrical load is excessive.
Turn on all electrical loads including the heater blower,
head lights, rear window defogger, etc. and check to see
if the malfunction occurs.
±
INTRODUCTION TITLE±NAMEIN±21
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SERVICE SPECIFICATIONS
SERVICE DATA
Idle speedMagnetic clutch no engagedApprox. 700 rpm
Magnetic clutch engaged Approx. 700 rpm
Magnetic clutch clearance0.5 + 0.15 mm0.020 + 0.006 in.
TORQUE SPECIFICATIONS
Part tightenedN Vmkgf Vcmft Vlbf
Suction hose X Compressor2525018
Discharge hose X Compressor25250 18
Compressor X EngineBolt 49500 36
Nut 29300 22
Liquid tube X Receiver10100 7
Liquid tube X Condenser10100 7
Discharge tube X Condenser10100 7
Expansion valve X Evaporator5.455 48 in. Vlbf
Suction tube X A/C Unit10100 7
Liquid tube X A/C Unit10100 7
Equalizer tube X EPR25250 18
Pressure switch X Liquid tube101007
±
AIR CONDITIONING SYSTEM Service SpecificationsAC±141
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Lexus Supports ASE CertificationPage 1 of 4
Title:
R-12 AIR CONDITIONER SYSTEM
RETROFIT
Models:
'90±'93 ES 250/300, SC 400/300, LS 400
Technical Service
Information Bulletin
April 3, 1998
AC001±98
The following information should be used for guidance when retrofitting veh\
icle air
conditioning systems from R±12 to R134a refrigerant.
1990±1992 model year LS 400, 1990±1991 model year ES 250, 1992±1993 model
year ES 300, 1992±1993 model year SC 300, 1992±1993 model year SC 400
All parts required for retrofit are available through the normal parts s\
ystem:
IDENTIFICATIONREQUIRED PARTS & MATERIALS
MODELCOMPRESSORRETROFIT SETRECEIVERND OIL 8CHARGE
LS 40010PA2088471±16050170 cc1000 g
ES 25010PA17V88840±33020 (1)
l
88471±12040100 cc650 g
ES 300plus
90099±14044 (2)SC 30010PA1790099±14044 (2)
90099±14045 (1)88471±16050150 cc900 g
SC400
90099 14045 (1)g
NOTE:
Retrofit Set 88840±33020 includes: 88374±33010 Low pressure side service fitting adaptor (7/16±20 UNF)
88374±33020 High pressure side service fitting adaptor (3/8±20 UNF)
88723±20040 R134a ªUSE ONLYº label (ND Oil 8 for 10P, 10PA compressor)
88723±33050 Retrofit Caution Label
90099±14046 Piping O±rings for discharge hose (quantity 2)
Required for all models (not included in set): 90099±14044 Receiver O±rings (quantity 2)
08885±09107 ND±Oil 8
Also available as needed: 88374±33040 L±shaped low pressure side service fitting adaptor
88374±33050 L±shaped high pressure side service fitting adaptor
OP CODENWCDESCRIPTIONTIMEOPNT1T2
Not Applicable to Warranty
Affected Vehicles page 1 . . . . . . . . . .
Service Precautions page 3 . . . . . . . .
Retrofit Kit Parts page 1 . . . . . . . . . . .
Required Parts page 2 . . . . . . . . . . . . . Required Tools & Materials page 2
. . .
Retrofitting Overview page 2 . . . . . . . . .
Repair Procedures page 3 . . . . . . . . . . .
Warranty Information page 1 . . . . . . . . .
HEATING & AIR CONDITIONING
Introduction
Affected
Vehicles
Parts
Information
Warranty
Information
Table of
Contents
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R±12 AIR CONDITIONER SYSTEM RETROFIT ± AC001±98 April 3, 1998
Page 2 of 4
A. Required Equipment:
1. R±12 recovery/recycling/recharging equipment
2. R134a recovery/recycling/recharging equipment
3. Measuring cylinder (for compressor oil)
4. Valve core remover for service valves
5. Air conditioner service tool set
6. Torque Wrench Set, P/N 00002±50284±01, includes the following*: 14 mm 00002±51410±01
17 mm 00002±51710±01
22 mm 00002±52216±01
27 mm 00002±52724±01
B. Required Parts & Materials: **
1. R134a Refrigerant
2. Service Fitting Adaptors
3. Caution Labels
4. ND±OIL 8 compressor oil (PAG type oil)
5. Receiver
6. O±Rings for compressor, line & hose connections ***
7. Loctite 262 or equivalent
* required size dependent upon model.
** see parts information section of this bulletin on page 1.
*** it is not necessary to replace any O±rings on ES 300, SC 300 and SC 400 models\
.
A. Refrigerant and Oil Charges
Oil and refrigerant charge amounts are different after the R±12 system has been
retrofitted to R134a. Refrigerant charge amounts are less, while oil ch\
arge
amounts are greater, compared to R±12 system requirements. Refer to the
ND OIL
8
and CHARGE columns in ªParts Informationº table on page 1 for proper amounts\
.
B. System Performance A slight decrease in system performance may be noticed on some vehicles \
under
certain operating conditions.
C. Refrigerant Pressures
R134a high side pressures are greater than that of R±12 above ambient\
temperatures of 68 °F.
D. Flushing Requirements There is no need to remove or flush R±12 mineral oil from the system.\
Simply
charge the system with the specified amount of ND±Oil 8 to provide pr\
oper
lubrication.
E. Use of Sight Glass Mineral based R±12 oil remains and circulates in the A/C system and d\
oes not
dissolve in R134a refrigerant. This results in a cloudy appearance at th\
e sight
glass making it impossible to judge the refrigerant charge amount by us\
ing the
sight glass method. To prevent misdiagnosis on retrofit vehicles, apply black
paint to the sight glass on block±joint (FF) type Receivers. Union\
±nut joint (BAG)
type retrofit Receivers are manufactured without a sight glass.
Required
Tools &
Materials
Retrofitting Overview
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