Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

INSPECT INTEGRATION NO.1 RELAY (MAIN RELAY)

CHECK ECM (HT1B, HT2B VOLTAGE)

CHECK WIRE HARNESS (HEATED OXYGEN SENSOR - ECM AND INTEGRATION RELAY (MAIN RELAY))

DESCRIPTION

1. Refer to DTC P0136 (Toyota Fortuner RM000000TEO00JX.html).
   

HINT:

1. When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the heated oxygen sensor (HO2S) heater in fail-safe mode. Fail-safe mode continues until the ignition switch is turned OFF.
   
2. The ECM uses 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.
   

HINT:

1. Bank 1 refers to the bank that includes the No. 1 cylinder.
   
2. Bank 2 refers to the bank that does not include the No. 1 cylinder.
   
3. Sensor 1 refers to the sensor closer to the engine assembly.
   
4. Sensor 2 refers to the sensor farther away from the engine assembly.
   

MONITOR DESCRIPTION

1. 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 appropriate temperature and the difference of the oxygen concentrations between the inside and outside surface of the sensor is large, the zirconia element will generate voltage signals. In order to increase the oxygen concentration detecting capacity of the zirconia element, the ECM supplements the heat from the exhaust with the heat from the heating element inside the sensor. When the current in the sensor is out of the standard operating range, the ECM interprets this as a fault in the heated oxygen sensor heater and sets a DTC.
   
2. Example:
   
3. The ECM will set a high current DTC if the current in the sensor is more than 2 A when the heater is OFF. Similarly, the ECM will set a low current DTC if the current is less than 0.3 A when the heater is ON.
   

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

1. Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.
   
2. Sensor 1 refers to the sensor mounted before the Three-Way Catalytic Converter (TWC) and is located near the engine assembly.
   
3. Sensor 2 refers to the sensor mounted after the TWC and is located far from the engine assembly.
   

1. Disconnect the H12 and H13 heated oxygen sensor connectors.
   

2. Measure the resistance of the sensor.
   
   

   Standard resistance:

   Bank 1

   Tester Connection	Condition	Specified Condition
   1 (HT1B) - 2 (+B)	20°C (68°F)	11 to 16 Ω
   1 (HT1B) - 4 (E2)	-	10 kΩ or higher

   Bank 2

   Tester Connection	Condition	Specified Condition
   1 (HT2B) - 2 (+B)	20°C (68°F)	11 to 16 Ω
   1 (HT2B) - 4 (E2)	-	10 kΩ or higher

1. Disconnect the 1J integration relay connector from the engine room junction block (Toyota Fortuner RM0000014TJ00HX.html).
   

2. Measure the voltage of the MAIN relay.
   

   Standard resistance:

   Tester Connection	Condition	Specified Condition
   1J-5 - Body ground	Ignition switch ON	10 to 14 V

1. Turn the ignition switch ON.
   

2. Measure the voltage of the ECM connector.
   

   Standard voltage:

   Tester Connection	Specified Condition
   E15-1 (HT1B) - E17-1 (E1)	9 to 14 V
   E16-5 (HT2B) - E17-1 (E1)	9 to 14 V

1. Disconnect the H12 or H13 sensor connectors.
   

2. Disconnect the E15 or E16 ECM connector.
   

3. Disconnect the 1J integration relay connector from the engine room junction block (Toyota Fortuner RM0000014TJ00HX.html).
   

4. Measure the resistance of the wire harness side connectors.
   
   

   Standard resistance:

   Bank 1 Sensor 2

   Tester Connection	Specified Condition
   H12-1 (HT1B) - E15-1 (HT1B)	Below 1 Ω
   H12-2 (+B) - 1J-5	Below 1 Ω
   H12-1 (HT1B) or E15-1 (HT1B) - Body ground	10 kΩ or higher
   H12-2 (+B) or 1J-5 - Body ground	10 kΩ or higher

   Bank 2 Sensor 2

   Tester Connection	Specified Condition
   H13-1 (HT2B) - E16-5 (HT2B)	Below 1 Ω
   H13-2 (+B) - 1J-5	Below 1 Ω
   H13-1 (HT2B) or E16-5 (HT2B) - Body ground	10 kΩ or higher
   H13-2 (+B) or 1J-5 - Body ground	10 kΩ or higher