1996 TOYOTA T100 lights

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DI−55
1996 TOYOTA T100 (RM449U)
DTC P0171 System too Lean (Fuel Trim)
DTC P0172 System too Rich (Fuel Trim)
CIRCUIT DESCRIPTION
Fuel trim refers to the feedback compensation value compared against the basic injection time. Fuel trim
includes short−term fuel trim and long−term fuel trim.
Short−term fuel trim is the short−term fuel compensation used to maintain the air−fuel ratio at its ideal
theoretical value. The signal from the heated oxygen sensor indicates whether the air−fuel ratio is RICH or
LEAN compared to the ideal theoretical value, triggering a reduction in fuel volume if the air−fuel ratio is rich,
and an increase in fuel volume if it is lean.
Long−term fuel trim is overall fuel compensation carried out long−term to compensate for continual deviation
of the short−term fuel trim from the central value due to individual engine differences, wear over time and
changes in the usage environment.
If both the short−term fuel trim and long−term fuel trim are LEAN or RICH beyond a certain value, it is de-
tected as a malfunction and the MIL lights up.
DTC No.DTC Detecting ConditionTrouble Area
P0171
When air fuel ratio feedback is stable after engine warming
up, fuel trim is considerably in error on RICH side
(2 trip detection logic)
Air intake (hose loose)
Fuel line pressure
Injector blockage
Heated oxygen sensor (bank 1 sensor 1) malfunction
Mass air flow meter
Engine coolant temp. sensor
P0172
When air fuel ratio feedback is stable after engine warming
up, fuel trim is considerably in error on LEAN side
(2 trip detection logic)
Fuel line pressure
Injector leak, blockage
Heated oxygen sensor (bank 1 sensor 1) malfunction
Mass air flow meter
Engine coolant temp. sensor
HINT:
When the DTC P0171 is recorded, the actual air−fuel ratio is on the LEAN side. When DTC P0172 is
recorded, the actual air−fuel ratio is on the RICH side.
If the vehicle runs out of fuel, the air−fuel ratio is LEAN and DTC P0171 is recorded. The MIL then
comes on.
If the total of the short−term fuel trim value and long−term fuel trim value is within ± 25 %, the system
is functioning normally.
INSPECTION PROCEDURE
1 Check air induction system (See page MF−1).
NG Repair or replace.
OK
DI0TO−03

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− DIAGNOSTICSENGINE (3RZ−FE)
1996 TOYOTA T100 (RM449U)
DTC P0300 Random/Multiple Cylinder Misfire Detected
DTC P0301 Cylinder 1 Misfire Detected
DTC P0302 Cylinder 2 Misfire Detected
DTC P0303 Cylinder 3 Misfire Detected
DTC P0304 Cylinder 4 Misfire Detected
CIRCUIT DESCRIPTION
Misfire: The ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in
the crankshaft rotation for each cylinder.
The ECM counts the number of times the engine speed change rate indicates that misfire has occurred. And
when the misfire rate equals or exceeds the count indicating that the engine condition has deteriorated, the
MIL lights up.
If the misfire rate is high enough and the driving conditions will cause catalyst overheating, the MIL blinks
when misfiring occurs.
DTC No.DTC Detecting ConditionTrouble Area
P0300Misfiring of random cylinders is detected during any
particular 200 or 1,000 revolutionsIgnition system
Injector
Fuel line pressure
EGR
Compression pressure
Valve clearance not to specification
Valve timing
Mass air flow meter
Engine coolant temp. sensor
P0301
P0302
P0303
P0304For any particular 200 revolutions for engine, misfiring is
detected which can cause catalyst overheating
(This causes MIL to blink)
For any particular 1,000 revolutions for engine, misfiring is
detected which causes a deterioration in emissions
(2 trip detection logic)
HINT:
When the 2 more codes for a misfiring cylinder are recorded repeatedly but no random misfire code is re-
corded, it indicates that the misfires were detected and recorded at different times.
DI0TP−03

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ENGINE CONTROL SYSTEM Check Sheet
Customer’s Name
Driver’s Name
Date Vehicle
Brought in
License No.
Model and Model
Year
Frame No.
Engine Model
Odometer Reading
km
miles
Problem Symptoms
Engine does
not Start
Difficult to
Start
Poor Idling
Poor
Driveability
Engine Stall
Others
Engine does not crankNo initial combustionNo complete combustion
Engine cranks slowly
Other
Incorrect first idleIdling rpm is abnormalHigh ( rpm)Low ( rpm)
Rough idling
Other
HesitationBack fireMuffler explosion (after−fire)Surging
Knocking
Other
Soon after startingAfter accelerator pedal depressed
After accelerator pedal released
During A/C operation
Shifting from N to D
Other
Dates Problem
Occurred
Problem Frequency
Condition When
Problem Occurs
Weather
Engine Operation
Engine Temp. Place Outdoor Temp.Constant
Sometimes ( times per day/month)Once only
Other
Fine
CloudyRainySnowyVarious/Other
Hot
Warm CoolCold (approx. °F/ °C)
Highway
SuburbsInner cityUphillDownhill
Rough road
Other
Cold
Warming upAfter warming upAny temp.Other
Starting
Just after starting ( min.)IdlingRacing
Driving
Constant speedAccelerationDeceleration
A/C switch ON/OFF
Other
Condition of MILRemains on Sometimes lights up Does not light up
NormalMalfunction code(s) (code )
Freezed frame data ( )
NormalMalfunction code(s) (code )
Freezed frame data ( )
Normal Mode
(Precheck)
Check Mode DTC InspectionInspector’s
Name
DI−128
− DIAGNOSTICSENGINE (5VZ−FE)
1996 TOYOTA T100 (RM449U)
CUSTOMER PROBLEM ANALYSIS CHECK

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DI0UB−02
FI7231
TOYOTA Hand−Held Tester
DLC 3
− DIAGNOSTICSENGINE (5VZ−FE)
DI−129
1996 TOYOTA T100 (RM449U)
PRE−CHECK
1. DIAGNOSIS SYSTEM
(a) Description
When troubleshooting OBD II vehicles, the only dif-
ference from the usual troubleshooting procedure
is that you connect to the vehicle the OBD II scan
tool complying with SAE J1978 or TOYOTA hand−
held tester, and read off various data output from
the vehicle’s ECM.
OBD II regulations require that the vehicle’s on−
board computer lights up the Malfunction Indicator
Lamp (MIL) on the instrument panel when the com-
puter detects a malfunction in the computer itself or
in drive system components which affect vehicle
emissions. In addition to the MIL lighting up when
a malfunction is detected, the applicable Diagnostic
Trouble Codes (DTCs) prescribed by SAE J2012
are recorded in the ECM memory (See page
DI−140).
If the malfunction does not reoccur in 3 trips, the MIL goes off
but the DTCs remain recorded in the ECM memory.
To check the DTCs, connect the OBD II scan tool or
TOYOTA hand−held tester to the Data Link Con-
nector 3 (DLC3) on the vehicle. The OBD II scan
tool or TOYOTA hand−held tester also enables you
to erase the DTCs and check freezed frame data
and various forms of engine data (For operating
instructions, see the OBD II scan tool’s instruction
book.).
DTCs include SAE controlled codes and manufac-
turer controlled codes. SAE controlled codes must
be set as prescribed by the SAE, while manufactur-
er controlled codes can be set freely by the
manufacturer within the prescribed limits (See DTC
chart on page DI−140).

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Flashing
ON
OFF
0.13 Seconds
DI−132
− DIAGNOSTICSENGINE (5VZ−FE)
1996 TOYOTA T100 (RM449U)
NOTICE:
When simulating symptoms with an OBD II scan tool (ex-
cluding TOYOTA hand−held tester) to check the DTCs, use
normal mode. For code on the DTC chart subject to ”2 trip
detection logic”, turn the ignition switch OFF after the
symptom is simulated the 1st time. Then repeat the simula-
tion process again. When the problem has been simulated
twice, the MIL lights up and the DTCs are recorded in the
ECM.
3. INSPECT DIAGNOSIS (Check Mode)
HINT:
TOYOTA hand−held tester only:
Compared to the normal mode, the check mode has an in-
creased sensitivity to detect malfunctions.
Furthermore, the same diagnostic items which are detected in
the normal mode can also be detected in the check mode.
(a) Check the DTC.
(1) Initial conditions
Battery positive voltage 11 V or more
Throttle valve fully closed
Transmission in ”P” or ”N” position
Air conditioning switched OFF
(2) Turn the ignition switch OFF.
(3) Prepare the TOYOTA hand−held tester.
(4) Connect the TOYOTA hand−held tester to DLC3 at
the lower of the instrument panel.
(5) Turn the ignition switch ON and push the TOYOTA
hand−held tester switch ON.
(6) Switch the TOYOTA hand−held tester normal mode
to check mode (Check that the MIL flashes.).
(7) Start the engine. (The MIL goes out after the engine
start.)
(8) Simulate the conditions of the malfunction de-
scribed by the customer.
NOTICE:
Leave the ignition switch ON until you have checked the
DTCs, etc.
(9) After simulating the malfunction conditions, use the
TOYOTA hand−held tester diagnosis selector to
check the DTCs and freezed frame data, etc.
HINT:
Take care not to turn the ignition switch OFF. Turning the ignition
switch OFF switches the diagnosis system from check mode to
normal mode. so all DTCs, etc. are erased.
(10) After checking the DTC, inspect the applicable cir-
cuit.

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DI−140
− DIAGNOSTICSENGINE (5VZ−FE)
1996 TOYOTA T100 (RM449U)
DIAGNOSTIC TROUBLE CODE CHART
SAE CONTROLLED
HINT:
Parameters listed in the chart may not be exactly the same as your reading due to the type of instrument
or other factors.
If a malfunction code is displayed during the DTC check in check mode, check the circuit for that code listed
in the table below. For details of each code, turn to the page referred to under the ’’See Page ’’ for the respec-
tive ’’DTC No.’’ in the DTC chart.
DTC No.
(See Page)Detection ItemTrouble AreaMIL*Memory
P0100
(DI−149)Mass Air Flow Circuit
MalfunctionOpen or short in mass air flow meter circuit
Mass air flow meter
ECM

P0101
(DI−153)Mass Air Flow Circuit
Range/Performance
Problem
Mass air flow meter
P0110
(DI−154)Intake Air Temp. Circuit
MalfunctionOpen or short in intake air temp. sensor circuit
Intake air temp. sensor
ECM

P0115
(DI−158)Engine Coolant Temp. Circuit
MalfunctionOpen or short in engine coolant temp. sensor circuit
Engine coolant temp. sensor
ECM

P0116
(DI−162)Engine Coolant Temp. Circuit
Range/Performance ProblemEngine coolant temp. sensor
Cooling system
P0120
(DI−163)Throttle/Pedal Position
Sensor/Switch ”A” Circuit
MalfunctionOpen or short in throttle position sensor circuit
Throttle position sensor
ECM

P0121
(DI−168)Throttle/Pedal Position
Sensor/Switch ”A” Circuit
Range/Performance Problem
Throttle position sensor
P0125
(DI−169)Insufficient Coolant Temp. for
Closed Loop Fuel ControlOpen or short in heated oxygen sensor (bank 1 sensor 1)
circuit
Heated oxygen sensor (bank 1 sensor 1)

P0130
(DI−172)Heated Oxygen Sensor Circuit
Malfunction (Bank 1 Sensor 1)Heated oxygen sensor
Fuel trim malfunction
P0133
(DI−175)Heated Oxygen Sensor Circuit
Slow Response
(Bank 1 Sensor 1)
Heated oxygen sensor
P0135
(DI−176)Heated Oxygen Sensor Heater
Circuit Malfunction
(Bank 1 Sensor 1)Open or short in heater circuit of heated oxygen sensor
Heated oxygen sensor
ECM

P0136
(DI−178)Heated Oxygen Sensor Circuit
Malfunction
(Bank 1 Sensor 2)
Heated oxygen sensor
P0141
(DI−176)Heated Oxygen Sensor Heater
Circuit Malfunction
(Bank 1 Sensor 2)
Same as DTC No. P0135
*:  MIL lights up

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DI−141
1996 TOYOTA T100 (RM449U) DTC No.
(See Page)
Detection ItemTrouble AreaMILMemory
P0171
(DI−180)System too Lean
(Fuel Trim)
Air intake (hose loose)
Fuel line pressure
Injector blockage
Heated oxygen sensor (bank 1 sensor 1) malfunction
Mass air flow meter
Engine coolant temp. sensor
*1
P0172
(DI−180)System too Rich
(Fuel Trim)
Fuel line pressure
Injector leak, blockage
Heated oxygen sensor (bank 1 sensor 1) malfunction
Mass air flow meter
Engine coolant temp. sensor
*1
P0300
(DI−183)Random/Multiple Cylinder
Misfire DetectedIgnition system
Injector
Fuel line pressure
EGR*3
Compression pressure
Valve clearance not to specification
Valve timing
Mass air flow meter
Engine coolant temp. sensor*2
P0301
P0302
P0303
P0304
P0305
P0306
(DI−183)Misfire Detected
− Cylinder 1
− Cylinder 2
− Cylinder 3
− Cylinder 4
− Cylinder 5
− Cylinder 6
*2
P0325
(DI−188)Knock Sensor 1 Circuit
MalfunctionOpen or short in knock sensor 1 circuit
Knock sensor 1 (looseness)
ECM
*1
P0330
(DI−188)Knock Sensor 2 Circuit
MalfunctionOpen or short in knock sensor 2 circuit
Knock sensor 2 (looseness)
ECM
*1
P0335
(DI−191)Crankshaft Position Sensor
”A” Circuit Malfunction
Open or short in crankshaft position sensor circuit
Crankshaft position sensor
Starter
ECM
*1 
P0340
(DI−194)Camshaft Position Sensor
Circuit Malfunction
Open or short in camshaft position sensor circuit
Camshaft position sensor
Starter
ECM
*1 
P0401*3
(DI−196)Exhaust Gas Recirculation
Flow Insufficient Detected
EGR valve stuck closed
Short in VSV circuit for EGR
Open in EGR gas temp. sensor circuit
EGR hose disconnected
ECM
*1 
P0402*3
(DI−206)Exhaust Gas Recirculation
Flow Excessive Detected
EGR valve stuck open
EGR VSV open malfunction
Open in VSV circuit for EGR
Short in EGR gas temp. sensor circuit
ECM
*1
P0420
(DI−210)Catalyst System Efficiency
Below Threshold
Three−way catalytic converter
Open or short in heated oxygen sensor (bank 1 sensor 1, 2)
circuit
Heated oxygen sensor (bank 1 sensor 1, 2)
*1
*1: MIL lights up
*2: MIL lights up or blinking
*3: Only for 2WD models with a load capacity of 0.5 ton and regular cab.

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− DIAGNOSTICSENGINE (5VZ−FE)
1996 TOYOTA T100 (RM449U) DTC No.
(See Page)
Detection ItemTrouble AreaMIL*Memory
P0441
(DI−212)Evaporative Emission Control
System Incorrect Purge Flow
Open or short in VSV circuit for EVAP
VSV for EVAP
Open or short in vapor pressure sensor circuit
Vapor pressure sensor
Open or short in VSV circuit for vapor pressure sensor
VSV for vapor pressure sensor
Vacuum hose cracked, holed, blocked, damaged or
disconnected
Charcoal canister cracked, holed or damaged

P0500
(DI−226)Vehicle Speed Sensor
Malfunction
Open or short in No.1 vehicle speed sensor circuit
No.1 vehicle speed sensor
ECM
Speedometer cable

P0505
(DI−228)Idle Control System
Malfunction
IAC valve is stuck or closed
Open or short in IAC valve circuit
Open or short in A/C signal circuit
Air intake (hose loose)

P0510
(DI−231)Closed Throttle Position Switch
MalfunctionOpen in closed throttle position switch circuit
Closed throttle position switch
ECM

*:  MIL lights up
MANUFACTURER CONTROLLED
DTC No.
(See Page)Detection ItemTrouble AreaMIL*Memory
P1300
(DI−235)Igniter Circuit Malfunction
Open or short in IGF or IGT circuit from igniter to ECM
Igniter
ECM

P1335
(DI−241)Crankshaft Position Sensor
Circuit Malfunction
(during engine running)Open or short in crankshaft position sensor circuit
Crankshaft position sensor
Starter
ECM
−
P1500
(DI−242)Starter Signal Circuit Malfunction
Open or short in starter signal circuit
Open or short in ignition switch or starter relay circuit
ECM
−
P1600
(DI−244)ECM BATT MalfunctionOpen in back up power source circuit
ECM
P1605
(DI−246)Knock Control CPU MalfunctionECM
P1780
(DI−247)Park/Neutral Position Switch
MalfunctionShort in park/neutral position switch circuit
Park/neutral position switch
ECM

*: −  MIL does not light up,   MIL lights up