DTC    P0037    Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
DTC    P0038    Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2)
DTC    P0057    Oxygen Sensor Heater Control Circuit Low (Bank 2 Sensor 2)
DTC    P0058    Oxygen Sensor Heater Control Circuit High (Bank 2 Sensor 2)

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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)	5 to 10 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)	5 to 10 Ω at 20°C (68°F)
   HT2B (1) - E2 (4)	10 kΩ or higher

3. Reconnect the HO2 sensor connector.
   

NG	REPLACE HEATED OXYGEN SENSOR

OK

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

2. Measure the resistance of the 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.
   

NG	REPLACE INTEGRATION RELAY

OK

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.
      

OK	REPLACE ECM

NG

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 (2)	Below 1 Ω
      +B (L57-2) - EFI NO. 2 fuse (2)	Below 1 Ω

      Standard resistance (Check for short):

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

   4. Reconnect the HO2 sensor connector.
      

   5. Reconnect the EFI NO. 2 fuse.
      

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

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 (A7-2)	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.
      

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK
REPLACE ECM