P0037 Heated Oxygen (HO2) sensor heater current less than 0.25 A (1 trip detection logic)

DESCRIPTION

The heated oxygen sensor (HO2S) is used to monitor oxygen in the exhaust gas. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal "stoichiometric" ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The ECM (Included in HV Control ECU) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometirc.
The HO2S generates a voltage between 0.1 and 0.9 volts in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes "Lean". The ECM interprets Lean when the HO2S voltage is below 0.45 volts. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes "Rich". The ECM interprets Rich when the HO2S voltage is above 0.45 volts.

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 (Included in HV Control ECU) 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.
   

DTC No.	DTC Detection Condition	Trouble Area
P0037 P0057	Heated Oxygen (HO2) sensor heater current less than 0.25 A (1 trip detection logic)	Open in HO2 sensor heater circuit HO2 sensor heater Integration relay HV Control ECU
P0038 P0058	Heated Oxygen (HO2) sensor heater current more than 2 A (1 trip detection logic)	Short in HO2 sensor heater circuit HO2 sensor heater Integration relay HV Control ECU

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.
   

WIRING DIAGRAM

Refer to DTC P0136 (Click here).

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. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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)

1. Disconnect the H20 or H11 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
   HT1B (2) - +B (1)	11 to 16 Ω at 20°C (68°F)
   HT1B (2) - E2 (3)	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.

NG	REPLACE HEATED OXYGEN SENSOR

OK

2. INSPECT IGCT RELAY

1. Remove the IGCT relay from the engine room R/B.

2. Inspect the IGCT relay.

   Standard resistance:

   Terminal Connection	Specified Condition
   3 - 5	10 kΩ or higher
   3 - 5	Below 1 Ω (When battery voltage applied to terminals 1 and 2)

3. Reinstall the IGCT relay.

NG	REPLACE INTEGRATION RELAY

OK

3. INSPECT HV CONTROL ECU (HT1B OR HT2B VOLTAGE)

1. Turn the ignition switch ON.

2. Measure the voltage between the terminals of the H29, H32 and H33 HV Control ECU connectors.

   Standard voltage:

   Terminal Connection	Specified Condition
   HT1B (H29-21) - E1 (H32-5)	9 to 14 V
   HT2B (H33-33) - E1 (H32-5)	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 HV CONTROL ECU

NG

4. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - IGCT NO.4 FUSE)

1. Check the harness and connector between the HO2 sensor and IGCT fuse.

   1. Disconnect the H11 or H20 HO2 sensor connector.

   2. Remove the IGCT No.4 fuse from the R/B No.3.

   3. Measure the resistance between the terminals of the HO2 sensor and IGCT No.4 fuse.

      Standard resistance:

      Terminal Connection	Specified Condition
      +B (H20-1) - IGCT No.4 fuse (2)	Below 1 Ω
      +B (H11-2) - IGCT No.4 fuse (2)	Below 1 Ω

      Standard resistance:

      Terminal Connection	Specified Condition
      +B (H20-1) or IGCT No.4 fuse (2) - Body ground	10 kΩ or higher
      +B (H11-2) or IGCT No.4 fuse (2) - Body ground	10 kΩ or higher

   4. Reconnect the HO2 sensor connector.

   5. Reconnect the IGCT No.4 fuse.

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

5. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - HV CONTROL ECU)

1. Check the harness and connector between the HV Control ECU and HO2 sensor.

   1. Disconnect the H20 or H11 HO2 sensor connector.

   2. Remove the H29 and H33 HV Control ECU connector.

   3. Measure the resistance between the terminals of the HO2 sensor and HV Control ECU.

      Standard resistance:

      Terminal Connection	Specified Condition
      HT1B (H20-1) - HT1B (H29-21)	Below 1 Ω
      HT2B (H11-2) - HT2B (H33-33)	Below 1 Ω
      HT1B (H20-1) or HT1B (H29-21) - Body ground	10 kΩ or higher
      HT2B (H11-2) or HT2B (H33-33) - Body ground	10 kΩ or higher

   4. Reconnect the HO2 sensor connector.

   5. Reconnect the HV Control ECU connector.

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK
REPLACE HV CONTROL ECU