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 RELAY (EFI MAIN RELAY)

INSPECT ECM (HT1B OR HT2B VOLTAGE)

CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - EFI NO. 2 FUSE)

CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)

DESCRIPTION

1. Refer to DTC P0136 on page Click here
   

HINT:

1. Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.
   
2. When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the Heated Oxygen (HO2) Sensor heater in fail-safe mode. Fail-safe mode continues until the engine switch is turned off.
   


3. The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The HO2 sensor heater circuit uses a relay on the B+ side of the circuit.
   
   
   
   
   
   

HINT:

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

MONITOR DESCRIPTION

1. The sensing position of the Heated Oxygen (HO2) 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 he 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. When the current in the sensor heater is outside the standard operating range, the ECM interprets this as a malfunction in the sensor heater and sets a DTC.
   
2. Example:
   
3. The ECM sets DTC P0038 or P0058 when the current in the HO2 sensor heater is more than 2 A. Conversely, when the heater current is less than 0.3 A, DTC P0037 or P0057 is set.
   

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

1. If other DTCs relating to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
   
2. Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions 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.
   

1. Disconnect the L34 or L57 heated oxygen (HO2) sensor connectors.
   

2. Measure the resistance between the terminals of the HO2 sensor connector.
   

   Standard resistance (Bank 1 sensor 2):

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

   Standard resistance (Bank 2 sensor 2):

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

3. Reconnect the HO2 sensor connector.
   

1. Remove the integration relay from the engine room No. 2 junction block.
   

2. Measure the resistance of EFI MAIN relay.
   

   Standard resistance:

   Terminal Connection	Specified Condition
   2A-8 - 2A-5	10 kΩ or higher
   2A-8 - 2A-5	Below 1 Ω (when battery voltage applied to terminals 2A-7 and 2A-6)

3. Reinstall the integration relay.
   

1. Turn the engine switch on (IG).
   

2. Measure the voltage between the terminals of the A7 and E7 ECM connectors.
   

   Standard voltage:

   Terminal Connection	Specified Condition
   HT1B (A7-2) - E1 (E7-7)	9 to 14 V
   HT2B (A7-1) - E1 (E7-7)	9 to 14 V

   HINT:

   1. The HT1B means the heated oxygen sensor bank 1 sensor 2.
      
   2. The HT2B means the heated oxygen sensor bank 2 sensor 2.
      

1. Check the harness and connector between the HO2 sensor and EFI NO. 2 fuse.
   

   1. Disconnect the L34 or L57 HO2 sensor connector.
      

   2. Remove the EFI NO. 2 fuse from the engine room No. 2 relay block.
      

   3. Measure the resistance.
      

      Standard resistance (Check for open):

      Terminal Connection	Specified Condition
      +B (L34-2) - EFI NO. 2 fuse terminal (2)	Below 1 Ω
      +B (L57-2) - EFI NO. 2 fuse terminal (2)	Below 1 Ω

      Standard resistance (Check for short):

      Terminal Connection	Specified Condition
      +B (L34-2) or EFI NO. 2 fuse terminal (2) - Body ground	10 kΩ or higher
      +B (L57-2) or EFI NO. 2 fuse terminal (2) - Body ground	10 kΩ or higher

   4. Reconnect the HO2 sensor connector.
      

   5. Reconnect the EFI NO. 2 fuse.
      

1. Check the harness and connector between the ECM and HO2 sensor.
   

   1. Disconnect the L34 or L57 HO2 sensor connector.
      

   2. Remove the A7 ECM connector.
      

   3. Measure the resistance.
      

      Standard resistance (Check for open):

      Terminal Connection	Specified Condition
      HT (L34-1) - HT1B (A47-2)	Below 1 Ω
      HT2B (L57-1) - HT2B (A7-1)	Below 1 Ω

      Standard resistance (Check for short):

      Terminal Connection	Specified Condition
      HT (L34-1) or HT1B (A7-2) - Body ground	10 kΩ or higher
      HT2B (L57-1) or HT2B (A7-1) - Body ground	10 kΩ or higher

   4. Reconnect the HO2 sensor connector.
      

   5. Reconnect the ECM connector.