1996 TOYOTA LAND CRUISER Workshop Manual

DI−44
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
INSPECTION PROCEDURE
1 Check for open and short in harness and connector between ECM and heated
oxygen sensor (bank 1 sensor 1) (See page IN−28 ).
NG Repair or replace harness or connector
(See page IN−28 ).
OK
2 Check for heated oxygen sensor (bank 1 sensor 1) data.
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect the OBD II scan tool or TOYOTA hand−held tester to the DLC3.
(c) Warm up engine to normal operating temp.
CHECK:
Read the heated oxygen sensor (bank 1 sensor 1) output voltage and sho\
rt −term fuel trim.
RESULT:
PatternHeated o xygen sensor (bank 1 sensor 1) 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−51 ).
3
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P18349
−
DIAGNOSTICS ENGINE
DI−45
1996 LAND CRUISER (RM451U)
3 Check the output voltage of heated oxygen sensor (bank 1 sensor 1) during
idling.
PREPARATION:
Warm up the heated oxygen sensor (bank 1 sensor 1) with the engine at 2\
,500 rpm for approx. 90 sec.
CHECK:
Use the OBD II scan tool or T OYOTA hand−held tester read the output voltage of the heated oxygen sensor
(bank 1 sensor 1) during idling.
OK:
Heated oxygen sensor (bank 1 sensor 1) 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(See page DI−43 ).
NG
Replace heated oxygen sensor
(bank 1 sensor 1).
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DI−46
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
DTC P0133 Heated Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 1)
CIRCUIT DESCRIPTION
Refer to DTC P0125 (Insufficient Coolant Temp. for Closed Loop Fuel Control) on page DI−40.
DTC No.DTC Detecting ConditionTrouble Area
P0133
Response time for the heated oxygen sensor’s voltage output
to change from rich to lean, or from lean to rich, is 1 sec. or
more during idling after the engine is warmed up
(2 trip detection logic)
Heated oxygen sensor (bank 1 sensor 1)
HINT:
Sensor 1 refers to the sensor closer to the engine body.
INSPECTION PROCEDURE
1 Are there any other codes (besides DTC P0133) being output?
YES Go to relevant DTC chart.
NO
Replace heated oxygen sensor
(bank 1 sensor 1).
DI5PB−02
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BE6653
P24460A00950
ON
HT1HT2
(−) (+)
−
DIAGNOSTICS ENGINE
DI−47
1996 LAND CRUISER (RM451U)
DTC P0135 Heated Oxygen Sensor Heater Circuit
Malfunction (Bank 1 Sensor 1)
DTC P0141 Heated Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 (Insufficient Coolant Temp. for Closed Loop Fuel Control) on page DI−40.
DTC No.DTC Detecting ConditionTrouble Area
P0135
P0141
When the heater operates, heater current exceeds 2 A
(2 trip detection logic)Open or short in heater circuit of heated oxygen sensor
 Heated oxygen sensor heater
 ECM
Heater current of 0.25 A or less when the heater operates
(2 trip detection logic)
HINT:
Sensor 1 refers to the sensor closer to the engine body.
Sensor 2 refers to the sensor farther away from the engine body.
WIRING DIAGRAM
Refer to DTC P0125 (Insufficient Coolant Temp. for Closed Loop Fuel Control) on page DI−40 for WIRING
DIAGRAM.
INSPECTION PROCEDURE
1 Check voltage between terminals HT1, HT2 of ECM connector and body ground.
PREPARATION:
(a) Remove instrument panel speaker No.1 panel (See page SF−65 ).
(b) Turn 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−28 ).
NG
DI5PC−02
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DI−48
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
2 Check resistance of heated oxygen sensor heater (See page SF−64).
NG Replace heated oxygen sensor.
OK
Check and repair harness or connector between EFI main relay (Marking: EFI) \
and heated oxygen
sensor (bank 1 sensor 1, 2) and ECM (See page IN−28).
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−
DIAGNOSTICS ENGINE
DI−49
1996 LAND CRUISER (RM451U)
DTC P0136 Heated Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 (Insufficient Coolant Temp. for Closed Loop Fuel Control) on page DI−40.
DTC No.DTC Detecting ConditionTrouble Area
P0136
Voltage output of the heated oxygen sensor (bank 1 sensor 2)
remains at 0.4 V or more or 0.5 V or less when the vehicle is
driven at 40 km/h (25 mph) or more after the engine is warmed
up. (2 trip detection logic).
Heated oxygen sensor (bank 1 sensor 2)
HINT:
Sensor 2 refers to the sensor farther away from the engine body.
WIRING DIAGRAM
Refer to DTC P0125 (Insufficient Coolant Temp. for Closed Loop Fuel Control) on page DI−40 for WIRING
DIAGRAM.
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 (bank 1 sensor 2) (See page IN−28 ).
NG Repair or replace harness or connector.
OK
DI5PD−02
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DI−50
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
3 Check the output voltage of heated oxygen sensor (bank 1 sensor 2).
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect the OBD II scan tool or TOYOTA hand−held tester to the DLC3.
(c) Warm up engine to normal operating temp.
CHECK:
Read voltage output of heated oxygen sensor (bank 1 sensor 2) when eng\
ine suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 min. using 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 con-nected.
NG
Replace heated oxygen sensor
(bank 1 sensor 2).
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−
DIAGNOSTICS ENGINE
DI−51
1996 LAND CRUISER (RM451U)
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 a\
ir −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 devi-
ation of the short−term fuel trim form 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 the air fuel ratio feedback is stable after engine warming
up, the fuel trim is considerably in error on the RICH side.
(2 trip detection logic)
 Air intake (hose loose)
 Fuel line pressure
 Injector blockage, leak
 Heated oxygen sensor (bank 1 sensor 1) malfunction
 Mass air flow meter
 Engine coolant temp. sensor
P0172
When the air fuel ratio feedback is stable after engine warming
up, the fuel trim is considerably in error on the LEAN side.
(2 trip detection logic)
Fuel line pressure
 Injector blockage, leak
 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 total of the short −term fuel trim value and long −term fuel trim value is within + 30 − − 35 %, the
system is functioning normally.
If the vehicle runs out of fuel, the air −fuel ratio is LEAN and DTC P0171 is recorded. The MIL then come
on.
INSPECTION PROCEDURE
1 Check air induction system (See page SF−1 ).
NG Repair or replace
OK
DI5PE−02
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