When any of these DTCs is stored, the ECM enters fail-safe mode. The ECM turns off the heated oxygen sensor heater in fail-safe mode. The ECM continues operating in fail-safe mode until the ignition switch is turned off.

The ECM provides a pulse-width modulated control circuit to adjust the current through the heater. The heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.

Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2). 1GR-FE ENGINE CONTROL. Land Cruiser URJ200 URJ202 GRJ200 VDJ200

DTC No.	DTC Detection Condition	Trouble Area
P0037 P0057	The heater current is below the specified value while the heater is operating (1 trip detection logic).	Open in heated oxygen sensor heater circuit Heated oxygen sensor heater (sensor 2) Integration relay (EFI) ECM
P0038 P0058	The heater current is higher than the specified value while the heater is operating (1 trip detection logic).	Short in heated oxygen sensor heater circuit Heated oxygen sensor heater (sensor 2) Integration relay (EFI) ECM
P102D P105D	The heater current is higher than the specified value while the heater is not operating (1 trip detection logic).	ECM

MONITOR DESCRIPTION

The sensing portion of the heated oxygen sensor has a zirconia element which is used to detect the oxygen concentration in the exhaust gas. If the zirconia element is at the appropriate temperature and the difference between the oxygen concentrations surrounding the inside and outside surfaces of the sensor is large, the zirconia element generates voltage signals. In order to increase the oxygen concentration detecting capacity of the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor.

Heated oxygen sensor heater range check (P0037, P0038, P0057, P0058, P102D and P105D):

The ECM monitors the current applied to the heated oxygen sensor heater to check the heater for malfunctions.

If the heater current is outside the normal range, the signal transmitted by the heated oxygen sensor becomes inaccurate. When the current in the heated oxygen sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.

WIRING DIAGRAM

Refer to DTC P0136 ().

INSPECTION PROCEDURE

NOTICE:

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

HINT:

Sensor 2 refers to the sensor mounted behind the Three-way Catalytic Converter (TWC) and located far from the engine assembly.

Read freeze frame data using the GTS. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

Bank 1 refers to the bank that includes the No. 1 cylinder*.
*: The No. 1 cylinder is the cylinder which is farthest from the transmission.

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

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

Sensor 2 refers to the sensor farthest away from the engine assembly.

1.INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

Inspect the heated oxygen sensor ().

REPLACE HEATED OXYGEN SENSOR ()

OK

2.CHECK TERMINAL VOLTAGE (+B OF HEATED OXYGEN SENSOR)

Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2). 1GR-FE ENGINE CONTROL. Land Cruiser URJ200 URJ202 GRJ200 VDJ200

Disconnect the heated oxygen sensor connector.

Turn the ignition switch to ON.

Measure the voltage according to the value(s) in the table below.

Standard Voltage:
Tester Connection Switch Condition Specified Condition
C20-2 (+B) - Body ground Ignition switch ON 11 to 14 V
C21-2 (+B) - Body ground Ignition switch ON 11 to 14 V

Text in Illustration
*A	for Bank 1 Sensor 2
*B	for Bank 2 Sensor 2
*a	Front view of wire harness connector (to Heated Oxygen Sensor)

Go to step 5

OK

3.CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)

Disconnect the heated oxygen sensor connector.

Disconnect the ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

for LHD
Tester Connection	Condition	Specified Condition
C20-1 (HT1B) - C45-45 (HT1B)	Always	Below 1 Ω
C21-1 (HT2B) - C45-44 (HT2B)	Always	Below 1 Ω
C20-1 (HT1B) or C45-45 (HT1B) - Body ground	Always	10 kΩ or higher
C21-1 (HT2B) or C45-44 (HT2B) - Body ground	Always	10 kΩ or higher

for RHD
Tester Connection	Condition	Specified Condition
C20-1 (HT1B) - C46-45 (HT1B)	Always	Below 1 Ω
C21-1 (HT2B) - C46-44 (HT2B)	Always	Below 1 Ω
C20-1 (HT1B) or C46-45 (HT1B) - Body ground	Always	10 kΩ or higher
C21-1 (HT2B) or C46-44 (HT2B) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.CHECK WHETHER DTC OUTPUT RECURS (DTC P0037, P0038, P0057, P0058, P102D AND/OR P105D)

Connect the GTS to the DLC3.

Turn the ignition switch to ON.

Turn the GTS on.

Clear the DTCs ().

Start the engine.

Allow the engine to idle for 1 minute or more.

Read the output pending DTCs using the GTS.

Result
Result	Proceed to
No pending DTC is output	A
Pending DTC P0037, P0038, P0057, P0058, P102D and/or P105D is output	B

REPLACE ECM ()

CHECK FOR INTERMITTENT PROBLEMS ()

5.INSPECT INTEGRATION RELAY (EFI)

Inspect the integration relay (EFI) ().

REPLACE INTEGRATION RELAY

OK

6.CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - INTEGRATION RELAY (EFI))

Disconnect the heated oxygen sensor connector.

Remove the integration relay from the engine room relay block.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
C20-2 (+B) - 1B-4	Always	Below 1 Ω
C21-2 (+B) - 1B-4	Always	Below 1 Ω
C20-2 (+B) or 1B-4 - Body ground	Always	10 kΩ or higher
C21-2 (+B) or 1B-4 - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK ECM POWER SOURCE CIRCUIT ()

Tester Connection	Switch Condition	Specified Condition
C20-2 (+B) - Body ground	Ignition switch ON	11 to 14 V
C21-2 (+B) - Body ground	Ignition switch ON	11 to 14 V