1998 TOYOTA LAND CRUISER relay

P20302
FI7210
A00798
Atmosphere
Housing
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platinum Electrode
Heater
Coating (Ceramic)
Exhaust Gas CoverIdeal Air-Fuel Mixture
Output Voltage
Richer - Air Fuel Ratio - Leaner
A21040
Reference(Bank 1 Sensor 1 System Drawing) :
ECM
EFI or ECD Relay
EFI or ECD
Fuse No. 1 From
Battery
GroundOX1A
MREL HT1A
Duty
Control Heater
Sensor Heated Oxygen Sensor
EFI or ECD
Fuse No. 2
E2 DI-50
- DIAGNOSTICSENGINE
243 Author
: Date
:
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way cata-
lytic 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 heated oxygen sensor has the characteristic which 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 ex-
haust gas and provide the ECM with feedback to control the air-fuel ratio.
When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the heated
oxygen sensor informs the ECM of the LEAN condition (low voltage, i.e. less than 0.45 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 heated oxygen sensor informs the ECM of the RICH condition (high voltage,
i.e. more than 0.45 V). The ECM judges by the voltage output from the heated oxygen sensor whether the
air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the
heated oxygen sensor causes output of abnormal voltage, this disables the ECM for performing an 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 temperature of the exhaust gas is
low) current flows to the heater to heat the sensor for accurate oxygen concentration detection.
HINT:
The ECM provides a pulse width modulated control circuit to adjust current through the heater. The heated
oxygen sensor heater circuit uses a relay on the B+ side of the circuit.

- DIAGNOSTICSENGINE
DI-51
244 Author
: Date
:
DTC No.DTC Detecting ConditionTrouble Area
P0031
P0037
Heater current is 0.25 A or less when the heater operates with

Open in heater circuit of heated oxygen sensor

Heated ox
ygen sensor heaterP0037
P0051
P0057
Heater current is 0.25 A or less when the heater o erates with
more than 10.5 V positive battery voltage

Heated oxygen sensor heater

EFI or ECD relay

ECM
P0032
P0038
P0052
P0058
When heater operates, heater current exceeds 2.0 A

Short in heater circuit of heated oxygen sensor

Heated oxygen sensor heater

EFI or ECD relay

ECM
HINT:

Bank 1 refers to bank the includes cylinder No. 1.

Bank 2 refers to bank that does not includes cylinder No. 1.

Sensor 1 refers to the sensor closer to the engine assembly.

Sensor 2 refers to the sensor farther away from the engine assembly.
MONITOR DESCRIPTION
The sensing portion of the heated oxygen sensor has a zirconia element which is used to detect oxygen
concentration in the exhaust. If the zirconia element is at the proper temperature and difference of the oxy-
gen concentration between the inside and outside surface of sensor is large, the zirconia element will gener-
ate voltage signals. In order to increase the oxygen concentration detecting capacity in the zirconia element,
the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor. When
current in the sensor is out of the standard operating range, the ECM interprets this as a fault in the heated
oxygen sensor and sets a DTC.
Example:
The ECM will set a high current DTC if the current in the sensor is more than 2.0 A when the heater is OFF.
Similarly, the ECM will set a low current DTC if the current is less than 0.25 A when the heater is ON.

A21367
ECM
MREL
E2
HT2A
OX2A
OX1A HT1A
HT2B
OX2B
OX1B HT1B 8
28
33
22
234
25
21
295 E9
E5
E6
E6
E6E6
E6
E6
E6 E6 J/B No. 5
2 15
5C
5D B-W
1
1 1
1
12
3 4 Engine Room R/B
EFI or ECD Relay
W-B
B-Y
B-Y
B-Y
1
IX2SB
Cowl Side J/B LH
EFI or ECD No. 245
5
2A2Q
Engine Room J/B
43 44
11
1
1C 1A 1B
1BEFI or ECD No. 1
F15
FL Block
291 2
3
43
8119 5
11 2
3
41
43
1
3 2
43B-W
EB3
EB3
EB3 EB3 EB3
EB3
EB1BR
BR
BRBR B-G
EA ECD C C C C C J17
J/C
MAIN
BatteryW-B+B
E1HT
OX HT
OX +B
E1H7 Heated Oxygen Sensor
(Bank 2 Sensor 1)
H5 Heated Oxygen Sensor
(Bank 1 Sensor 1)If1
B W
W
BY
W
B LL (*1)
(*1)
(*1)
(*1) (*1)
(*1)BR-W BR-W
B-Y
B-Y
B-Y
W-B
B-YR-B R-B
+B
E1HT
OXHT
OX +B
E1
BR-WH6 Heated Oxygen Sensor
(Bank 1 Sensor 2)
D
*1: Shielded H8 Heated Oxygen Sensor
(Bank 2 Sensor 2)R B-Y
2
BR-W
BR-W BR-W
BR-W BR-W BR-W
B-Y
B-Y
B-Y DI-54
- DIAGNOSTICSENGINE
247 Author
: Date
:
WIRING DIAGRAM

A21543
1
23
4 EFI or ECD Relay
A19522A19630
HT1A HT1BE6
ECM Connector HT2A
HT2B
DI-56
- DIAGNOSTICSENGINE
249 Author
: Date
:
2 Check EFI or ECD relay.
PREPARATION:
Remove the EFI or ECD relay from the engine room R/B.
CHECK:
Inspect the EFI or ECD relay.
OK:
Terminal No.ConditionSpecified Condition
2 - 4ConstantContinuity
UsuallyNo Continuity
1 - 3Apply B+ between
terminals 2 and 4Continuity
NG Replace EFI or ECD relay.
OK
3 Check voltage between terminals HT1A, HT2A, HT1B, HT2B of ECM connectors
and body ground.
PREPARATION:
Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals of the ECM connectors
and body ground.
HINT:

Connect terminal HT1A to the bank 1 sensor 1.

Connect terminal HT1B to the bank 1 sensor 2.

Connect terminal HT2A to the bank 2 sensor 1.

Connect terminal HT2B to the bank 2 sensor 2.
OK:
Tester ConnectionSpecified Condition
HT1A (E6-4) - Body ground9 to 14 V
HT1B (E6-5) - Body ground9 to 14 V
HT2A (E6-33) - Body ground9 to 14 V
HT2B (E6-25) - Body ground9 to 14 V
OK Replace ECM (See page SF-60).
NG
Check and repair harness or connector between EFI or ECD relay and heated oxygen sensor, and
heated oxygen sensor and ECM (See page IN-36).

A21361
ECM
MRELVG
E2G
8 E530
E5 29 M1
Mass Air Flow Meter
Battery EFI or ECD No. 2
B-YCowl Side J/B LH
10 5
2A
2BB-YVG
E2G +B
34 5
G-W G-W G-WL-Y
L-Y L-Y
IW3
IW3IN2
IN2
E9 B-W B-WJ/B No. 5
15 2
5D 5C
W-B
Engine Room R/B
EFI or ECD Relay
1
1 1
1
1 2
34Engine Room J/B
4443
1B 1A
1B 1CW-B W-B
B-Y W-B
B-Y
F15
FL Block
MAIN2B-G
EA 1 11EFI or ECD No. 168
2 5
- DIAGNOSTICSENGINE
DI-59
252 Author
: Date
:
2004 LAND CRUISER (RM1071U)
COMPONENT OPERATING RANGE
ParameterStandard Value
Mass air flow meter voltage0.4 to 2.2 V
WIRING DIAGRAM

A20872
Cowl Side J/B LH:
EFI or ECD
No. 2 Fuse
A21226
Wire Harness Side:
Mass Air Flow Meter Connector
M1
+B
A20871
Engine Room J/B:
EFI or ECD
Relay
- DIAGNOSTICSENGINE
DI-63
256 Author
: Date
:
2004 LAND CRUISER (RM1071U)
5 Check for open and short in harness and connector between mass air flow meter
and EFI or ECD relay.
Check EFI or ECD No. 2 fuse:
PREPARATION:
Remove the EFI or ECD No. 2 fuse from the cowl side J/B LH.
CHECK:
Check for continuity in the EFI or ECD No. 2 fuse.
OK:
Continuity
Check harness and connector:
PREPARATION:
(a) Install the EFI or ECD No. 2 fuse.
(b) Disconnect the M1 mass air flow meter connector.
(c) Remove the EFI or ECD relay from the engine room R/B.
CHECK:
Check the resistance between the wire harness side connec-
tors.
OK:
Tester ConnectionSpecified Condition
+B (M1-3) - Engine Room J/B (EFI or
ECD relay terminal 1)Below 1 W
+B (M1-3) or Engine room J/B (EFI or
ECD relay terminal 1) -
Body ground
10 kW or higher
NG Repair or replace harness or connector.
OK
Check ECM power source circuit
(See page DI-345).

DI-106
- DIAGNOSTICSENGINE
299 Author
: Date
:
2004 LAND CRUISER (RM1071U)
DTC P0130 Oxygen Sensor Circuit (Bank 1 Sensor 1)
DTC P0150 Oxygen Sensor Circuit (Bank 2 Sensor 1)
DTC P2195 Oxygen Sensor Signal Stack Lean (Bank 1
Sensor 1)
DTC P2196 Oxygen Sensor Signal Stack Rich (Bank 1
Sensor 1)
DTC P2197 Oxygen Sensor Signal Stack Lean (Bank 2
Sensor 1)
DTC P2198 Oxygen Sensor Signal Stack Rich (Bank 2
Sensor 1)
CIRCUIT DESCRIPTION
Refer to DTC P0031 on page DI-49.
DTC No.Detection ItemTrouble Area
P0130
P0150
Output voltage 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)

Open or short in heated oxygen sensor circuit

Heated oxygen sensor


Heated oxygen sensor heater
P2195
P2197Output voltage of heated oxygen sensor remains at 0.55 V
or less, during idling after engine is warmed up
(2 trip detection logic)

Heated oxygen sensor heater

EFI or ECD relay

Air induction system

Fuel pressure
P2196
P2198Output voltage of heated oxygen sensor remains at 0.4 V or
more, during idling after engine is warmed up
(2 trip detection logic)
Fuel ressure

Injector

ECM
HINT:

Bank 1 refers to bank that includes cylinder No. 1.

Bank 2 refers to bank that does not includes cylinder No. 2.

Sensor 1 refers to the sensor closer to the engine assembly.

The heated oxygen sensor's output voltage and the short-term fuel trim value can be read using the
OBD II scan tool or hand-held tester.
DIC26-01

A20870
E1 +B
OX
+BHT
OX E1HT H5
H7
H6
H8
Components Side:
Bank1 Sensor1, Bank2 Sensor1
Bank1 Sensor2, Bank2 Sensor2
A21543
1
23
4 EFI or ECD Relay
- DIAGNOSTICSENGINE
DI-1 13
306 Author
: Date
:
2004 LAND CRUISER (RM1071U)
3 Check resistance of heated oxygen sensor heater.
PREPARATION:
Disconnect the H5, H6, H7 or H8 heated oxygen sensor con-
nector.
CHECK:
Measure resistance between terminals of the heated oxygen
sensor.
OK:
Tester ConnectionSpecified Condition
HT (H5-1) - +B (H5-2)11 to 16 W (20°C)
HT (H6-1) - +B (H6-2)11 to 16 W (20°C)
HT (H7-1) - +B (H7-2)11 to 16 W (20°C)
HT (H8-1) - +B (H8-2)11 to 16 W (20°C)
NG Replace heated oxygen sensor.
OK
4 Check EFI or ECD relay.
PREPARATION:
Remove the EFI or ECD relay from the engine room R/B.
CHECK:
Inspect the EFI or ECD relay.
OK:
Terminal No.ConditionSpecified Condition
2 - 4ConstantContinuity
UsuallyNo Continuity
1 - 3Apply B+ between
terminals 2 and 4Continuity
NG Replace EFI or ECD relay.
OK