1995 TOYOTA SUPRA engine

FOR VEHICLES EQUIPPED WITH
TRACTION CONTROL (TRAC) SYSTEM
When using a rear wheel two±wheel drum tester such as a
speedometer tester or chassis dynamometer, etc., or jacking
up the rear wheels and driving the wheels, always push in the
TRAC cut (ºTRAC OFFº) switch and turn the TRAC system
OFF.
CONFIRM TRAC SYSTEM IS OFF
1. Press the TRAC cut (ºTRAC OFFº) switch.
2. Check that the TRAC OFF indicator light comes on when the
TRAC system is turned off by the TRAC cut switch.
HINT: The TRAC indicator light should always operate right
after the engine is restarted.
3. Begin measurements.
4. Press the TRAC cut switch again to change the TRAC to
operative and check that the TRAC OFF indicator light goes
off.
HINT: The TRAC indicator light blinks when the TRAC system
is operative. IN±16
± INTRODUCTIONPRECAUTION

HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
A large number of ECU controlled systems are used in the TOYOTA SUPRA. In general, the ECU controlled
system is considered to be a very intricate system requiring a high level of technical knowledge and expert skill
to troubleshoot. However, the fact is that if you proceed to inspect the circuits one by one, troubleshooting 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 problem. This manual
is designed through emphasis of the above standpoint to help service technicians perform accurate and effec-
tive troubleshooting, and is compiled for the following major ECU controlled systems:
 Repair Manual System Page
 
Vol 1
 
1
 2JZ±GE Engine EG±381
 Vol. 1  1. 2JZ±GTE Engine EG±487
  
2
 A340E (2JZ±GE) Automatic Transmission AT1±31   2. A340E (2JZ±GTE) Automatic Transmission AT1±31 
 
 
  3.
 
 Anti±Lock Brake
 
 BR±51
 Vol 2  4. Traction Control BR±123
 Vol. 2  5. Supplemental Restraint System RS±41
   6. Theft Deterrent and Door Lock System BE±142
   7. Cruise Control BE±163
   8. Air Conditioning AC±13
The troubleshooting procedure and how to make use of it are described on the following pages.
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN±19

[2] SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the TOYOTA SUPRA fulfills various functions. The first function is the Diagnostic
Trouble 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. Another function is the Input
Signal Check which checks if the signals from various switches are sent to the ECU correctly. The air condition-
ing system has an Actuator Check function whereby the ECU automatically operates the actuators of the damp-
er and blowermotor, etc. to check the operation. By using these check functions, the problem areas can be nar-
rowed down quickly and troubleshooting can be performed effectively. Diagnostic functions are incorporated
in the following systems in the TOYOTA SUPRA.
 
 System
 
 
Diagnostic Trouble
Code Check 
 
Input Signal Check
(Sensor Check) 
 
Other Diagnosis
Function
 
 
 
 
 
 
Engine
Automatic Transmission
Anti±Lock Brake
Traction Control (Option)
Supplemental Restraint System
Cruise Control
Air Conditioning 
 
 
 
 
 
O (with Test Mode)
O (with Test Mode)
O
O
O
O
O 
 
 
 
 
 
O
O
O
O
O
O 
 
 
 
 
 Actuator Check
In diagnostic trouble code check, it is very important to determine whether the problem indicated by the diagnos-
tic trouble code is still occurring or occurred in the past but returned to normal at present. In addition, it must
be checked in the problem symptom check whether the malfunction indicated by the diagnostic trouble code
is directly related to the problem symptom or not. For this reason, the diagnostic trouble codes should be
checked before and after the symptom confirmation to determine the current conditions, as shown in the table
below. If this is not done, it may, depending on the case, result in unnecessary troubleshooting for normally oper-
ating systems, thus making it more difficult to locate the problem, or in repairs not pertinent to the problem.
Therefore, always follow the procedure in correct order and perform the diagnostic trouble code check.
DIAGNOSTIC TROUBLE CODE CHECK PROCEDURE
 
 
 
Diagnostic Trouble
Code Check (Make a
note of and then clear) 
 
 
Confirmation of
symptoms 
 
 
Diagnostic Trouble
Code Check 
 
 
Problem Condition
 
 
Diagnostic
Trouble Code
Display 
 
Problem symptoms
exist 
 
Same Diagnostic
trouble code is dis-
played 
 
Problem is still occurring in the diagnos-
tic circuit
 
 
 
 
 
%
 
 
 
 
 
 
 
 
 
 
Normal code is dis-
played 
 
 
 
 
The problem is still occurring in a place
other than in the diagnostic circuit. (The
diagnostic trouble code displayed first is
either for a past problem or it is a sec-
ondary problem.)
 
 %
 
 
No problem
symptoms exist 
 
 
 
The problem occurred in the diagnostic
circuit in the past.
 
 
Normal Code Display
%
 
 
Problem symptoms
exist 
 
Normal code is dis-
played 
 
The problem is still occurring in a place
other than in the diagnostic circuit.
 
 %
 
 
No problem
symptoms exist 
 
Normal code is dis-
played 
 
The problem occurred in a place other
than in the diagnostic circuit in the past.
IN±22± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS

[3] SYMPTOM SIMULATION
The most difficult case in troubleshooting is when there are no problem symptoms occurring. In such 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 how much experience a technician
has, or how skilled he may be, if he proceeds to troubleshoot without confirming the problem symptoms he will
tend to overlook something important in the repair operation and make a wrong 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 problem 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 confirmed, but the problem area
or parts must also be found out. To do this, narrow down the possible problem circuits according to the symptoms
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 confirming 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.
VIBRATION METHOD: When vibration seems to be the major cause.
CONNECTORS
Slightly shake the connector vertically and horizontally.
WIRE HARNESS
Slightly shake the connector 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 sen-
sor considered to be the problem cause and check if the
malfunction occurs.
HINT: Applying strong vibration to relays may result in
open relays. IN±24
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS

Heat the component that is the likely cause of the mal-
function 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.
HEAT METHOD: When the problem seems to occur when the suspect area is heated
WATER SPRINKLING METHOD: When the malfunction seems to occur on a rainy
day or in a high±humidity condition.
OTHER: When a malfunction seems to occur when electrical load is excessive.
Sprinkle water onto the vehicle and check to see if the
malfunction occurs.
NOTICE:
(1) Never sprinkle water directly into the engine compart-
ment, but indirectly change the temperature and humidity
by applying water spray onto the radiator front surface.
(2) Never apply water directly onto the electronic compo-
nents.
(Service hint)
If a vehicle is subject to water leakage, the leaked water may
contaminate the ECU. When testing a vehicle with a water leak-
age problem, special caution must be used.
Turn on all electrical loads including th3e heater blower,
head lights, rear window defogger, etc. and check to see
if the malfunction occurs.
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN±25

[4] DIAGNOSTIC TROUBLE CODE CHART
The inspection procedure is shown in the table below. This table permits efficient and accurate troubleshooting
using the diagnostic trouble codes displayed in the diagnostic trouble code check. Proceed with troubleshooting
in accordance with the inspection procedure given in the diagnostic chart corresponding to the diagnostic
trouble codes displayed. The engine diagnostic trouble code chart is shown below as an example.
IN±26± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS

GLOSSARY OF SAE AND TOYOTA TERMS
This glossary lists all SAE±J1930 terms and abbreviations used in this manual in compliance with SAE
recommendations, as well as their Toyota equivalents.
 
 
SAE ABBREVI±
ATIONS 
 SAE TERMS
 
 
TOYOTA TERMS
( ) ±± ABBREVIATIONS
 A/C Air Conditioning Air Conditioner
 ACL Air Cleaner Air Cleaner
AIRSecondary Air InjectionAir Injection (AI) AP Accelerator Pedal ± B+ Battery Positive Voltage +B, Battery Voltage BARO Barometric Pressure ±
 CAC Charge Air Cooler Intercooler
 CARB Carburetor Carburetor
 CFI Continuous Fuel Injection ±
 CKP Crankshaft Position Crank Angle
CLClosed LoopClosed Loop CMP Camshaft Position Cam Angle CPP Clutch Pedal Position ±
 CTOX Continuous Trap Oxidizer ±
 CTP Closed Throttle Position Idle ON (IDL ON)
 DFI Direct Fuel Injection (Diesel) Direct Injection (DI)
 DI Distributor Ignition ±
 
 
DLC1
DLC2
DLC3 
 
Data Link Connector 1
Data Link Connector 2
Data Link Connector 3 
 
1: Check Connector
2: Toyota Diagnosis Comunication Link (TDCL)
3: OBD II Diagnostic Connector
 DTC Diagnostic Trouble Code Diagnostic Code
 DTM Diagnostic Test Mode ±
 ECL Engine Control Level ±
 ECM Engine Control Module Engine ECU (Electronic Control Unit)
 ECT Engine Coolant Temperature Coolant Temperature, Water Temperature
(THW)
 
 
 
 
EEPROM
 
 
 
 
Electrically Erasable Programmable Read Only
Memory
 
 
 
 
Electrically Erasable Programmable Read Only
Memory (EEPROM),
Erasable Programmable Read Only Memory
(EPROM)
 
 
EFE 
 
Early Fuel Evaporation 
 
Cold Mixture Heater (CMH), Heat Control Valve
(HCV)
EGRExhaust Gas RecirculationExhaust Gas Recirculation (EGR) EI Electronic Ignition Toyota Distributorless Ignition (TDI) EM Engine Modification Engine Modification (EM) EPROM Erasable Programmable Read Only Memory Programmable Read Only Memory (PROM)
 EVAP Evaporative Emission Evaporative Emission Control (EVAP)
 FC Fan Control ±
 FEEPROM Flash Electrically Erasable Programmable
Read Only Memory ±
 
 FEPROM
 
 Flash Erasable Programmable Read Only
Memory 
 ±
 FF Flexible Fuel ±
 FP Fuel Pump Fuel Pump
 GEN Generator Alternator
 GND Ground Ground (GND)
HO2SHeated Oxygen SensorHeated Oxygen Sensor (HO2S)
± INTRODUCTIONGLOSSARY OF SAE AND TOYOTA TERMSIN±39

 IAC Idle Air Control Idle Speed Control (ISC)
IATIntake Air TemperatureIntake or Inlet Air Temperature ICM Ignition Control Module ± IFI Indirect Fuel Injection Indirect Injection IFS Inertia Fuel±Shutoff ±
 ISC Idle Speed Control ±
 KS Knock Sensor Knock Sensor
 MAF Mass Air Flow Air Flow Meter
 MAP Manifold Absolute Pressure Manifold Pressure
Intake Vacuum
 
 
 
MC
 
 
 
Mixture Control
 
 
 
Electric Bleed Air Control Valve (EBCV)
Mixture Control Valve (MCV)
Electric Air Control Valve (EACV)
 MDP Manifold Differential Pressure ±
 MFI Multiport Fuel Injection Electronic Fuel Injection (EFI)
MILMalfunction Indicator LampCheck Engine Light MST Manifold Surface Temperature ± MVZ Manifold Vacuum Zone ± NVRAM Non±Volatile Random Access Memory ±
 O2S Oxygen Sensor Oxygen Sensor, O2 Sensor (O2S)
 OBD On±Board Diagnostic On±Board Diagnostic (OBD)
 OC Oxidation Catalytic Converter Oxidation Catalyst Converter (OC), CCo
OPOpen LoopOpen Loop PAIR Pulsed Secondary Air Injection Air Suction (AS) PCM Powertrain Control Module ± PNP Park/Neutral Position ±
 PROM Programmable Read Only Memory ±
 PSP Power Steering Pressure ±
 
 
PTOX 
 
Periodic Trap Oxidizer 
 
Diesel Particulate Filter (DPF)
Diesel Particulate Trap (DPT)
RAMRandom Access MemoryRandom Access Memory (RAM) RM Relay Module ± ROM Read Only Memory Read Only Memory (ROM) RPM Engine Speed Engine Speed
 SC Supercharger Supercharger
 SCB Supercharger Bypass ±
 SFI Sequential Multiport Fuel Injection Electronic Fuel Injection (EFI), Sequential Injec-
tion
 SPL Smoke Puff Limiter ± SRI Service Reminder Indicator ± SRT System Readiness Test ±
 ST Scan Tool ±
 TB Throttle Body Throttle Body
 TBI Throttle Body Fuel Injection Single Point Injection
Central Fuel Injection (Ci)
 TC Turbocharger Turbocharger TCC Torque Converter Clutch Torque Converter TCM Transmission Control Module Transmission ECU (Electronic Control Unit)
 TP Throttle Position Throttle Position
 TR Transmission Range ±
IN±40± INTRODUCTIONGLOSSARY OF SAE AND TOYOTA TERMS