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

Engine. Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
2Az-Fe Engine Control System. Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

CONFIRMATION DRIVING PATTERN

INSPECTION PROCEDURE

INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

CHECK TERMINAL VOLTAGE (+B OF HO2 SENSOR)

INSPECT INTEGRATION RELAY (EFI MAIN RELAY)

CHECK HARNESS AND CONNECTOR (HO2 SENSOR - INTEGRATION RELAY)

CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM)

CHECK WHETHER DTC OUTPUT RECURS

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

DTC P0038 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2)


DESCRIPTION

  1. Refer to DTC P0136 (RAV4_ACA30 RM000000TEO056X_01.html).

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 ignition 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.


    Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.2Az-Fe Engine Control System.Sfi System. Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)


DTC No.
DTC Detection Condition
Trouble Area
P0037
Heated Oxygen (HO2) sensor heater current less than 0.3 A
(1 trip detection logic)
  1. Open in HO2 sensor heater circuit
  2. HO2 sensor heater (sensor 2)
  3. Integration relay (EFI MAIN relay)
  4. ECM
P0038
Heated Oxygen (HO2) sensor heater current more than 2 A
(1 trip detection logic)
  1. Short in HO2 sensor heater circuit
  2. HO2 sensor heater (sensor 2)
  3. Integration relay (EFI MAIN relay)
  4. ECM

MONITOR DESCRIPTION

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 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.
  1. Heated oxygen sensor heater range check (P0037 and P0038):
    The ECM monitors the current applied to the O2 sensor heater to check the heater for malfunctions. If the current is below the threshold value, the ECM determines that there is an open circuit in the heater. If the current is above the threshold value, the ECM determines that there is a short circuit in the heater.
    The ECM constantly monitors the current applied to the heater. If the ECM detects an open or short circuit, the ECM turns the MIL on and sets a DTC.
    If a malfunction is detected, the ECM cuts off the current applied to the heater.
    Example:
    The ECM sets DTC P0038 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 is set.

WIRING DIAGRAM

Refer to DTC P0136 (RAV4_ACA30 RM000000TEO056X_08.html).

CONFIRMATION DRIVING PATTERN

These DTCs are detected when the engine idles for 110 seconds or more.

INSPECTION PROCEDURE

HINT:
Read freeze frame data using the intelligent tester. 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.
1.INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.2Az-Fe Engine Control System.Sfi System. Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

  1. Disconnect the B19 Heated Oxygen (HO2) sensor connector.

  1. Measure the resistance of the HO2 sensor connector.

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

  1. Reconnect the HO2 sensor connector.



NG
REPLACE HEATED OXYGEN SENSOR
OK


2.CHECK TERMINAL VOLTAGE (+B OF HO2 SENSOR)
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.2Az-Fe Engine Control System.Sfi System. Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

  1. Disconnect the B19 HO2 sensor connector.

  1. Turn the ignition switch on (IG).

  1. Measure the voltage between the terminals of the B19 HO2 sensor connector and body ground.

    Standard voltage:
    Tester Connection
    		Specified Condition
    +B (B19-2) - Body ground
    		9 to 14 V

  1. Reconnect the HO2 sensor connector.



OK
Go to step 5
NG


3.INSPECT INTEGRATION RELAY (EFI MAIN RELAY)

  1. Remove the integration relay from the engine room relay block.



  1. Inspect the EFI MAIN fuse.



      Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.2Az-Fe Engine Control System.Sfi System. Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

    1. Remove the EFI MAIN fuse from the integration relay.

    2. Measure the EFI MAIN fuse resistance.

      Standard resistance:
      Below 1 Ω

    3. Reinstall the EFI MAIN fuse.

  1. Inspect the EFI MAIN relay.

    1. Measure the EFI MAIN relay resistance.

      Standard resistance:
      Tester Connection
      		Specified Condition
      1C-1 - 1A-4
      		10 kΩ or higher
      Below 1 Ω
      (Apply battery voltage between terminals 1A-2 and 1A-3)

  1. Reinstall the integration relay.



NG
REPLACE INTEGRATION RELAY
OK


4.CHECK HARNESS AND CONNECTOR (HO2 SENSOR - INTEGRATION RELAY)
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.2Az-Fe Engine Control System.Sfi System. Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

  1. Disconnect the B19 HO2 sensor connector.

  1. Remove the integration relay from the engine room No. 1 relay block (R/B).

  1. Measure the resistance.

    Standard resistance (Check for open):
    Tester Connection
    		Specified Condition
    +B (B19-2) - Engine room No. 1 R/B (1A-4)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connection
    		Specified Condition
    +B (B19-2) or Engine room No. 1 R/B (1A-4) - Body ground
    		10 kΩ or higher

  1. Reconnect the HO2 sensor connector.

  1. Reinstall the integration relay.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

CHECK ECM POWER SOURCE CIRCUIT

5.CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM)
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.2Az-Fe Engine Control System.Sfi System. Dtc P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

  1. Disconnect the B19 HO2 sensor connector.

  1. Disconnect the B32 ECM connector.

  1. Measure the resistance.

    Standard resistance (Check for open):
    Tester Connection
    		Specified Condition
    HT1B (B19-1) - HT1B (B32-47)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connection
    		Specified Condition
    HT1B (B19-1) or HT1B (B32-47) - Body ground
    		10 kΩ or higher

  1. Reconnect the HO2 sensor connector.

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


6.CHECK WHETHER DTC OUTPUT RECURS

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch on (IG).

  1. Turn the tester ON.

  1. Clear DTCs (RAV4_ACA30 RM000000PDK0AJX.html).

  1. Start the engine.

  1. Allow the engine to idle for 2 minutes or more.

  1. Select the following menu items: Powertrain / Engine and ECT / DTC.

  1. Read DTCs.


Result:

Display (DTC Output)
Proceed to
No output
A
P0037 or P0038
B


B
REPLACE ECM
A

CHECK FOR INTERMITTENT PROBLEMS