1996 TOYOTA T100 check engine light

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DI0T7−03
FI7231
TOYOTA Hand−Held Tester
DLC3
− DIAGNOSTICSENGINE (3RZ−FE)
DI−3
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 Code (DTC) prescribed by SAE J2012 are
recorded in the ECM memory (See page DI−13).
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 vaious 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−13).
The diagnosis system operates in normal mode
during normal vehicle use. It also has a check mode
for technicians to simulate malfunction symptoms
and troubleshoot. Most DTCs use 2 trip detection
logic* to prevent erroneous detection, and ensure
thorough malfunction detection. By switching the
ECM to check mode when troubleshooting, the
technician can cause the MIL to light up for a mal-
function that is only detected once or momentarily
(TOYOTA hand−held tester only) (See step 2).
*2 trip detection logic: When a logic malfunction is
first detected, the malfunction is temporarily stored
in the ECM memory. If the same malfunction is de-
tected again during the 2nd drive test, this 2nd
detection causes the MIL to light up.

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w/o Tachometer
w/ Tachometer
− DIAGNOSTICSENGINE (3RZ−FE)
DI−5
1996 TOYOTA T100 (RM449U)
HINT:
If your display shows ”UNABLE TO CONNECT TO VEHICLE”
when you have connected the cable of the OBD II scan tool or
TOYOTA hand−held tester to DLC3, turned the ignition switch
ON and operated the scan tool, there is a problem on the ve-
hicle side or tool side.
If communication is normal when the tool is connected to
another vehicle, inspect DLC3 on the original vehicle.
If communication is still not possible when the tool is con-
nected to another vehicle, the problem is probably in the
tool itself, so consult the Service Department listed in the
tool’s instruction manual.
2. INSPECT DIAGNOSIS (Normal Mode)
(a) Check the MIL.
(1) The MIL comes on when the ignition switch is turned
ON and the engine is not running.
HINT:
If the MIL does not light up, troubleshoot the combination meter.
(2) When the engine started, the MIL should go off. If
the lamp remains on, the diagnosis system has de-
tected a malfunction or abnormality in the system.
(b) Check the DTC.
NOTICE:
TOYOTA hand−held tester only: When the diagnosis sys-
tem is switched from normal mode to check mode, it
erases all DTCs and freezed frame data recorded in normal
mode. So before switching modes, always check the DTCs
and freezed frame data, and note them down.
(1) Prepare the OBD II scan tool (complying with SAE
J1978) or TOYOTA hand−held tester.
(2) Connect the OBD II scan tool or TOYOTA hand−
held tester to the DLC3 at the lower of the instru-
ment panel.
(3) Turn the ignition switch ON and turn the OBD II scan
tool or TOYOTA hand−held tester switch ON.
(4) Use the OBD II scan tool or TOYOTA hand−held
tester to check the DTCs and freezed frame data,
note them down. (For operating instructions, see
the OBD II scan tool’s instruction book.)
(5) See page DI−13 to confirm the details of the
DTCs.

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ON
OFFFlashing
0.13 Second
DI−6
− DIAGNOSTICSENGINE (3RZ−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 switch the TOYOTA
hand−held tester 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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DLC1 E1
TE1
SST
− DIAGNOSTICSENGINE (3RZ−FE)
DI−9
1996 TOYOTA T100 (RM449U)
5 Check idle speed.
PREPARATION:
(a) Warm up the engine to normal operating temperature.
(b) Switch off all the accessories.
(c) Switch off the air conditioning.
(d) Shift the transmission into ”N” position.
(e) Connect the OBD II scan tool or TOYOTA hand−held tester to the DLC3 on the vehicle.
CHECK:
Use CURRENT DATA to check the idle speed.
OK:
Idle speed: 750 ± 50 rpm
NG Proceed to problem symptoms table on page
DI−21.
OK
6 Check ignition timing.
PREPARATION:
(a) Warm up the engine to normal operating temperature.
(b) Shift the transmission into ”N” position.
(c) Keep the engine speed at idle.
(d) Using SST, connect terminals TE1 and E1 of the DLC1.
SST 09843−18020
(e) Using a timing light, connect the tester to the No.1 high−
tension cord.
CHECK:
Check the ignition timing.
OK:
Ignition timing: Approx. 5° BTDC at idle
NG Proceed to IGNITION and continue to trouble-
shoot.
OK
Proceed to problem symptoms table on page
DI−21.

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− DIAGNOSTICSENGINE (3RZ−FE)
DI−13
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−22)Mass Air Flow Circuit
MalfunctionOpen or short in mass air flow meter circuit
Mass air flow meter
ECM

P0101
(DI−26)Mass Air Flow Circuit
Range/Performance
Problem
Mass air flow meter
P0110
(DI−27)Intake Air Temp. Circuit
MalfunctionOpen or short in intake air temp. sensor circuit
Intake air temp. sensor
ECM

P0115
(DI−33)Engine Coolant Temp. Circuit
MalfunctionOpen or short in engine coolant temp. sensor circuit
Engine coolant temp. sensor
ECM

P0116
(DI−38)Engine Coolant Temp. Circuit
Range/Performance ProblemEngine coolant temp. sensor
Cooling system
P0120
(DI−39)Throttle/Pedal Position
Sensor/Switch ”A” Circuit
MalfunctionOpen or short in throttle position sensor circuit
Throttle position sensor
ECM

P0121
(DI−43)Throttle/Pedal Position
Sensor/Switch ”A” Circuit
Range/Performance Problem
Throttle position sensor
P0125
(DI−44)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−47)Heated Oxygen Sensor Circuit
Malfunction (Bank 1 Sensor 1)Heated oxygen sensor
Fuel trim malfunction
P0133
(DI−50)Heated Oxygen Sensor Circuit
Slow Response
(Bank 1 Sensor 1)
Heated oxygen sensor
P0135
(DI−51)Heated Oxygen Sensor Heater
Circuit Malfunction
(Bank 1 Sensor 1)Open or short in heater circuit of heated oxygen sensor
Heated oxygen sensor heater
 ECM

P0136
(DI−53)Heated Oxygen Sensor Circuit
Malfunction
(Bank 1 Sensor 2)
Heated oxygen sensor
P0141
(DI−51)Heated Oxygen Sensor Heater
Circuit Malfunction
(Bank 1 Sensor 2)
Same as DTC No. P0135
*:  MIL lights up

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Vehicle Speed
50 ∼ 65 km/h
(31 ∼ 40 mph)
Idling
IG SW OFF
1 ∼ 3 min. 1 min. Time
(1)(2)(3)(4)
(5)
− DIAGNOSTICSENGINE (3RZ−FE)
DI−47
1996 TOYOTA T100 (RM449U)
DTC P0130 Heated Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 1)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI−44.
DTC No.Detection ItemDTC Detecting ConditionTrouble AreaTrouble Area
P0130
Voltage output of heated oxygen sensor remains at 0.4 V or
more or 0.55 V or less, during idling after engine is warmed
up (2 trip detection logic)Heated oxygen sensor
Fuel trim malfunction
HINT:
Sensor 1 refers to the sensor closer to the engine body.
The heated oxygen sensor’s output voltage and the short−term fuel trim value can be read using the
OBD II scan tool or TOYOTA hand−held tester.
WIRING DIAGRAM
Refer to DTC P0125 on page DI−44.
CONFIRMATION DRIVING PATTERN
(1) Connect the TOYOTA hand−held tester to the DLC3.
(2) Switch the TOYOTA hand−held tester from normal mode to check mode (See page DI−13).
(3) Start the engine and warm it up with all the accessory switches OFF.
(4) Drive the vehicle at 50 − 65 km/h (31 − 40 mph) for 1 − 3 min. to warm up the heated oxygen sensor.
(5) Let the engine idle for 1 min.
HINT:
If a malfunction exists, the MIL will light up during step (5).
NOTICE:
If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
If you do not have a TOYOTA hand−held tester, turn the ignition switch OFF after performing steps
(3) to (5), then perform steps (3) to (5) again.
DI0TK−02

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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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ECM
Throttle Body
Throttle
ValveCheck
Valve
(for A/T)
EGR Vacuum Modulator
VSVEGR
Valve
P19921
R/B No.2
IG Switch
E7 E7
(M/T)(A/T)
E01
E1 ECM
E2 EGR
THG
E6 E6
E6 E6
622
14 3
99 1
BR−B G−WP
2
2
1 9 9
EA
W−R W−R
5 V
IE1W−REA1
W−B
2
3
22 22
2
25 B−W
EFIEFI Relay
VSV for EGR
EGR Gas
Temp. Sensor B−Y
EA1
4B−Y
1C17
1A3
W−R IGN
J/B
No.1
FromFrom Battery
5
1 DI−72
− DIAGNOSTICSENGINE (3RZ−FE)
1996 TOYOTA T100 (RM449U)
DTC P0401 Exhaust Gas Recirculation Flow Insufficient
Detected
CIRCUIT DESCRIPTION
The EGR system recirculates exhaust gas, which is controlled to the proper quantity to suit the driving condi-
tions, into the intake air mixture to slow down combustion, reduce the combustion temp. and reduce NOx
emissions. The amount of EGR is regulated by the EGR vacuum modulator according to the engine load.
If even one of the following conditions is fulfilled, the VSV is
turned ON by a signal from the ECM.
This results in atmospheric air acting on the EGR valve, closing
the EGR valve and shutting off the exhaust gas (EGR cut−off).
Under the following conditions, EGR is cut to maintain driveabil-
ity:
Before the engine is warmed up
During deceleration (throttle valve closed)
Light engine load (amount of intake air very small)
Engine racing
DTC No.DTC Detecting ConditionTrouble Area
P0401
After engine is warmed up and run at 80 km/h (50 mph)
for 3 to 5 min., EGR gas temp. sensor value does not exceed
35°C (95°F) above ambient air temp.
(2 trip detection logic)EGR valve stuck closed
Short in VSV circuit for EGR
Open in EGR gas temp. sensor circuit
EGR hose disconnected
ECM
WIRING DIAGRAM
DI0TU−03