1996 TOYOTA T100 check engine

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− DIAGNOSTICSENGINE (3RZ−FE)
1996 TOYOTA T100 (RM449U)
INSPECTION PROCEDURE
1 Check for open and short in harness and connector between ECM and heated
oxygen sensor (See page IN−26).
NG Repair or replace harness or connector.
OK
2 Check for heated oxygen sensor data.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand−held tester to the DLC3.
(b) Warm up the engine to normal operating temp.
CHECK:
Read heated oxygen sensor output voltage and short−term fuel trim.
HINT:
Read the values for the same bank.
RESULT:
PatternHeated oxygen sensor output voltageShort−term fuel trim
1Lean condition (Changes at 0.55 V or less)Changes at about + 20 %
2Rich condition (Changes at 0.4 V or more)Changes at about − 20 %
3Except 1 and 2
1, 2 Check fuel trim system (See page DI−55).
3

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− DIAGNOSTICSENGINE (3RZ−FE)
DI−49
1996 TOYOTA T100 (RM449U)
3 Check output voltage of heated oxygen sensor during idling.
PREPARATION:
Warm up the heated oxygen sensor with the engine at 2,500 rpm for approx. 90 sec.
CHECK:
Use the OBD II scan tool or TOYOTA hand−held tester read the output voltage of the heated oxygen sensor
during idling.
OK:
Heated oxygen sensor output voltage:
Alternates repeatedly between less than 0.4 V and more than 0.55 V (See the following table)
OK Perform confirmation driving pattern.
NG
Replace heated oxygen sensor.

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P23814
P23815
A00056
ON
For M/T
For M/THT1 (+) HT2 (+)
HT1 (+) HT2 (+)
DI−52
− DIAGNOSTICSENGINE (3RZ−FE)
1996 TOYOTA T100 (RM449U)
INSPECTION PROCEDURE
1 Check voltage between terminals HT1, HT2 of ECM connector and body ground.
PREPARATION:
(a) Remove the right cowl side trim (See page MF−50).
(b) Turn the ignition switch ON.
CHECK:
Measure voltage between terminals HT1, HT2 of ECM connec-
tor and body ground.
HINT:
Connect terminal HT1 to bank 1 sensor 1.
Connect terminal HT2 to bank 1 sensor 2.
OK:
Voltage: 9 − 14 V
OK Check and replace ECM (See page IN−26).
NG
2 Check resistance of heated oxygen sensor heater.
NG Replace heated oxygen sensor.
OK
Check and repair harness or connector be-
tween EFI main relay, heated oxygen sensor
and ECM.

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DI−53
1996 TOYOTA T100 (RM449U)
DTC P0136 Heated Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI−44.
DTC No.DTC Detecting ConditionTrouble Area
P0136
Voltage output of heated oxygen sensor (bank 1 Sensor 2)
remains at 0.4 V or more or 0.5 V or less when vehicle is driv-
en at 50 km/h
(31 mph) or more after engine is warmed up
(2 trip detection logic)
Heated oxygen sensor
HINT:
Sensor 2 refers to the sensor farther away from the engine body.
WIRING DIAGRAM
Refer to DTC P0125 on page DI−44.
INSPECTION PROCEDURE
1 Are there any other codes (besides DTC P0136) being output?
YES Go to relevant DTC chart.
NO
2 Check for open and short in harness and connector between ECM and heated
oxygen sensor (See page IN−26).
NG Repair or replace harness or connector.
OK
DI0TN−02

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− DIAGNOSTICSENGINE (3RZ−FE)
1996 TOYOTA T100 (RM449U)
3 Check output voltage of heated oxygen sensor (bank 1 sensor 2).
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand−held tester to the DLC3.
(b) Warm up the engine to normal operating temp.
CHECK:
Read voltage output of the heated oxygen sensor (bank 1 sensor 2) when the engine suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 min. using the accelerator pedal.
OK:
Heated oxygen sensor output voltage: Alternates from 0.4 V or less to 0.5 V or more
OK Check that each connector is properly
connected.
NG
Replace heated oxygen sensor.

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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)
2 Check for heated oxygen sensor (bank 1 sensor 1 ) data.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand−held tester to the DLC3.
(b) Warm up the engine to normal operating temp.
CHECK:
Read heated oxygen sensor output voltage and short−term fuel trim.
RESULT:
PatternHeated oxygen sensor output voltageShort−term fuel trim
1Lean condition (Changes at 0.55 V or less)Changes at about + 20 %
2Rich condition (Changes at 0.4 V or more)Changes at about − 20 %
3Except 1 and 2
3 Check for heated oxygen sensor (bank 1 sensor
1) (See page MF−49).
1, 2
3 Check fuel pressure (See page MF−5).
NG Check and repair fuel pump, pressure regulator,
fuel pipe line and filter (See page MF−10).
OK
4 Check injector injection (See page MF−16).
NG Replace injector.
OK

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DI−57
1996 TOYOTA T100 (RM449U)
5 Check mass air flow meter and engine coolant temp. sensor (See page
DI−22,DI−33).
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).