1996 TOYOTA T100 engine coolant

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P19555
A00046
ON
Engine Coolant
Temp. SensorECM
2
1
420
922
E2
E1 THW5 V
(A/T)
(M/T)E6
E6 E6E6
− DIAGNOSTICSENGINE (5VZ−FE)
DI−159
1996 TOYOTA T100 (RM449U)
INSPECTION PROCEDURE
HINT:
If DTCs P0110, P0115 and P0120 are output simultaneously, E2 (sensor ground) may be open.
1 Connect OBD II scan tool or TOYOTA hand−held tester and read value of
engine coolant temp.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand−held tester to the DLC3.
(b) Turn the ignition switch ON and push the OBD II scan tool or TOYOTA hand−held tester main switch
ON.
CHECK:
Read temp. value on the OBD II scan tool or TOYOTA hand−held tester.
OK:
Same as actual engine coolant temp.
HINT:
If there is open circuit, OBD II scan tool or TOYOTA hand−held tester indicates − 40°C (− 40°F).
If there is open circuit, OBD II scan tool or TOYOTA handheld tester indicates 140°C (284°F) or more.
NG − 40°C (− 40°F) ... Go to step 2.
140°C (284°F) or more ... Go to step 4.
OK
Check for intermittent problems
(See page DI−129).
2 Check for open in harness or ECM.
PREPARATION:
(a) Disconnect the engine coolant temp. sensor connector.
(b) Connect the sensor wire harness terminals together.
(c) Turn the ignition switch ON.
CHECK:
Read temp. value on the OBD II scan tool or TOYOTA
hand−held tester.
OK:
Temp. value: 140°C (284°F) or more
OK Confirm good connection at sensor.
If OK, replace engine coolant temp. sensor.
NG

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P19553
P20224
P20200A00104
ON
Engine Coolant
Temp. Sensor
2
1ECM
THW E2
THW E2
5 V
E2
E1420
922THW
E6 E6
E6 E6
(A/T) (M/T)
For M/T
For A/T
BE6653
P19554
A00048
ON
Engine Coolant
Temp. Sensor
2
1
420
922
5 V
E2
E1 THW
ECM
(A/T) (M/T)E6
E6
E6
E6
DI−160
− DIAGNOSTICSENGINE (5VZ−FE)
1996 TOYOTA T100 (RM449U)
3 Check for open in harness or ECM.
PREPARATION:
(a) Remove the right cowl side trim (See page SF−61).
(b) Connect between terminals THW and E2 of the ECM con-
nector.
HINT:
The engine coolant temp. sensor connector is disconnected.
Before checking, do a visual and contact pressure check for the
ECM connector (See page IN−26).
(c) Turn the ignition switch ON.
CHECK:
Read temp. value on the OBD II scan tool or TOYOTA
hand−held tester.
OK:
Temp. value: 140°C (284°F) or more
OK Open in harness between terminals E2 or THW,
repair or replace harness.
NG
Confirm good connection at ECM.
If OK, check and replace ECM.
4 Check for short in harness and ECM.
PREPARATION:
(a) Disconnect the engine coolant temp. sensor connector.
(b) Turn the ignition switch ON.
CHECK:
Read temp. value on the OBD II scan tool or TOYOTA
hand−held tester.
OK:
Temp. value: − 40°C (− 40°F)
OK Replace engine coolant temp. sensor.
NG

Downloaded from www.Manualslib.com manuals search engine BE6653
FI7056
P19798
FI7034
A00103
ON
ECM
Engine Coolant
Temp. Sensor
E2
E1
THW
E6 Connector
E6 Connector
For M/T
For A/T
5 V
− DIAGNOSTICSENGINE (5VZ−FE)
DI−161
1996 TOYOTA T100 (RM449U)
5 Check for short in harness or ECM.
PREPARATION:
(a) Remove the right cowl side trim (See page SF−61 ).
(b) Disconnect the E6 connector of the ECM.
HINT:
The engine coolant temp. sensor connector is disconnected.
(c) Turn the ignition switch ON.
CHECK:
Read temp. value on the OBD II scan tool or TOYOTA
hand−held tester.
OK:
Temp. value: − 40°C (− 40°F)
OK Repair or replace harness or connector.
NG
Check and replace ECM (See page IN−26).

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− DIAGNOSTICSENGINE (5VZ−FE)
1996 TOYOTA T100 (RM449U)
DTC P0116 Engine Coolant Temp. Circuit Range/
Performance problem
CIRCUIT DESCRIPTION
Refer to DTC P0115 on page DI−158.
DTC No.DTC Detecting ConditionTrouble Area
P0116
If THW − 7°C (19.4°F) at engine start, 20 min. or more
after starting engine, engine coolant temp. sensor value is
35°C (95°F) or less
(2 trip detection logic)
Engine coolant temp. sensor
Cooling system
If THW − 7°C (19.4°F) at engine start, 5 min. or more
after starting engine, engine coolant temp. sensor value is
35°C (95°F) or less
(2 trip detection logic)
INSPECTION PROCEDURE
HINT:
If DTCs P0115 and P0116 are output simultaneously, engine coolant temp. sensor circuit may be open.Per-
form troubleshooting of DTC P0115 first.
1 Are there any other codes (besides DTC P0116) being output?
YES Go to relevant DTC chart.
NO
2 Check thermostat (See page CO−9).
NG Replace thermostat.
OK
Replace engine coolant temp. sensor.
DI0UK−01

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A00027
Atomosphere
CoverIdeal Air−Fuel Mixture
Exhaust GasFlange
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platinum Electrode
Heater
Coating(Ceramic)
Output Voltage
Richer  Air−fuel Ratio  Leaner
− DIAGNOSTICSENGINE (5VZ−FE)
DI−169
1996 TOYOTA T100 (RM449U)
DTC P0125 Insufficient Coolant Temp. for Closed Loop
Fuel Control
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three−way
catalytic converter is used, but for the most efficient use of the three−way catalytic converter, the air−fuel
ratio must be precisely controlled so that it is always close to the stoichiometric air−fuel ratio.
The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the
stoichiometric air−fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust
gas and provide feedback to the computer for control of the air−fuel ratio.
When the air−fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen
sensor informs the ECM of the LEAN condition (small electromotive force: 0 V).
When the air−fuel ratio is RICHER than the stoichiometric air−fuel ratio the oxygen concentration in the ex-
haust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive
force: 1 V). The ECM judges by the electromotive force from the oxygen sensor whether the air−fuel ratio
is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor
causes output of abnormal electromotive force, the ECM is unable to perform accurate air−fuel ratio control.
The heated oxygen sensors include a heater which heats the Zirconia element. The heater is controlled by
the ECM. When the intake air volume is low (the temp. of the exhaust gas is low) current flows to the heater
to heat the sensor for accurate oxygen concentration detection.
DTC No.DTC Detecting ConditionTrouble Area
P0125
After engine is warmed up, heated oxygen sensor output
does not indicate RICH even once when conditions (a), (b),
(c) and (d) continue for at least 1.5 min.:
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40 − 100 km/h (25 − 62 mph)
(c) Throttle valve does not fully closed
(d) 140 sec. or more after starting engine
Open or short in heated oxygen sensor
(bank1 sensor 1) circuit
Heated oxygen sensor (bank 1 sensor 1)
DI0UN−01

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− DIAGNOSTICSENGINE (5VZ−FE)
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
detected 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 DTC P0171 is recorded, the actual air−fuel ratio is on the LEAN side. When DTC P0172 is re-
corded, 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 SF−5).
NG Repair or replace.
OK
DI0US−01

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− DIAGNOSTICSENGINE (5VZ−FE)
1996 TOYOTA T100 (RM449U)
5 Check mass air flow meter and engine coolant temp. sensor
(See page SF−29, SF−52).
NG Repair or replace.
OK
6 Check for spark and ignition (See page IG−1).
NG Repair or replace.
OK
Check and replace ECM (See page IN−26).

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DI−183
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
DTC P0305 Cylinder 5 Misfire Detected
DTC P0306 Cylinder 6 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 occur-
red.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
P0304
P0305
P0306For 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 of engine, misfiring is de-
tected which causes a deterioration in emission
(2 trip detection logic)
*: Only for 2WD models with a load capacity of 0.5 ton and regular cab.
HINT:
When the 2 or more codes for a misfiring cylinder are recorded repeatedly but no Random Misfire
code is
recorded, it indicates that the misfires were detected and recorded at different times.
DI0UT−01