Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

Engine. Lexus Gs430, Gs300. Uzs190 Grs190
3Gr-Fse Engine Control System. Lexus Gs430, Gs300. Uzs190 Grs190

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

INSPECT A/F HTR RELAY

INSPECT ECM

CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM, A/F SENSOR - A/F HTR RELAY)

DTC P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

DTC P0032 Oxygen (A/F) Sensor Heater Control Circuit High (Bank 1 Sensor 1)

DTC P0051 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 2 Sensor 1)

DTC P0052 Oxygen (A/F) Sensor Heater Control Circuit High (Bank 2 Sensor 1)


DESCRIPTION

Refer to DTC P2195 on page Click here.
HINT:
  1. Although the DTC titles say the oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
  2. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
  3. When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the A/F sensor heater in fail-safe mode. Fail-safe mode continues until the engine switch is turned off.

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


    Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fse Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)


DTC No.
DTC Detection Condition
Trouble Area
P0031
P0051
Air-Fuel Ratio (A/F) sensor heater (bank 1 sensor 1) current less than 0.8 A (1 trip detection logic)
  1. Open in A/F sensor heater (bank 1 sensor 1) circuit
  2. A/F sensor heater (bank 1 sensor 1)
  3. A/F HTR relay
  4. ECM
P0032
P0052
Air-Fuel Ratio (A/F) sensor heater (bank 2 sensor 2) current more than 10 A (1 trip detection logic)
  1. Short in A/F sensor heater (bank 2 sensor 2) circuit
  2. A/F sensor heater (bank 2 sensor 2)
  3. A/F HTR relay
  4. ECM
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

The ECM uses information from the Air-Fuel Ratio (A/F) sensor to regulate the air-fuel ratio and keep it close to the stoichiometric level. This maximizes the ability of the Three-Way Catalytic Converter (TWC) to purify the exhaust gases.
The A/F sensor detects oxygen levels in the exhaust gas and transmits the information to the ECM. The inner surface of the sensor element is exposed to the outside air. The outer surface of the sensor element is exposed to the exhaust gas. The sensor element is made of platinum coated zirconia and includes an integrated heating element.
The zirconia element generates a small voltage when there is a large difference in the oxygen concentrations between the exhaust gas and outside air. The platinum coating amplifies this voltage generation.
The A/F sensor is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful voltage signals without supplementary heating. The ECM regulates the supplementary heating using a duty-cycle approach to adjust the average current in the sensor heater element. If the heater current is outside the normal range, the signal transmitted by the A/F sensor will be inaccurate, as a result, the ECM will be unable to regulate air-fuel ratio properly.
When the current in the A/F sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and sets a DTC.
Example:
The ECM sets DTC P0032 or P0052 when the current in the A/F sensor heater is more than 10 A. Conversely, when the heater current is less than 0.8 A, DTC P0031 or P0051 is set.

WIRING DIAGRAM

Refer to DTC P2195 on page Click here

INSPECTION PROCEDURE

HINT:
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 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.
1.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fse Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the E68 or E65 A/F sensor connector.

  1. Measure the resistance between the terminals of the A/F sensor connector.

    Standard resistance (Bank 1 sensor 1):
    Tester Connection
    		Specified Condition
    HA1A (1) - +B (2)
    		1.8 to 3.4 Ω at 20°C (68°F)
    HA1A (1) - A1A- (4)
    		10 kΩ or higher
    Standard resistance (Bank 2 sensor 1):
    Tester Connection
    		Specified Condition
    HA2A (1) - +B (2)
    		1.8 to 3.4 Ω at 20°C (68°F)
    HA2A (1) - A2A- (4)
    		10 kΩ or higher

  1. Reconnect the A/F sensor connector.



NG
REPLACE AIR FUEL RATIO SENSOR
OK


2.INSPECT A/F HTR RELAY
Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fse Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Remove the A/F HTR relay from the engine room No. 2 relay block.

  1. Measure the A/F HTR relay resistance.

    Standard resistance:
    Tester Connection
    		Specified Condition
    3 - 5
    		10 kΩ or higher
    3 - 5
    		Below 1 Ω
    (when battery voltage applied to terminals 1 and 2)

  1. Reinstall the A/F HTR relay.



NG
REPLACE A/F HTR RELAY
OK


3.INSPECT ECM
Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fse Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Turn the engine switch on (IG).

  1. Measure the voltage between the terminals of the E45 ECM connector.

    Standard voltage:
    Tester Connection
    		Specified Condition
    HA1A (E45-6) - E04 (E45-5)
    		9 to 14 V
    HA2A (E45-4) - E04 (E45-5)
    		9 to 14 V
    HINT:
    1. The HA1A means the A/F sensor bank 1 sensor 1.
    2. The HA2A means the A/F sensor bank 2 sensor 1.


OK
REPLACE ECM
NG


4.CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM, A/F SENSOR - A/F HTR RELAY)
Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fse Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Check the harness and the connector between the ECM and the A/F sensor.

    1. Disconnect the E68 or E65 A/F sensor connector.

    2. Disconnect the E45 ECM connector.

    3. Measure the resistance.

      Standard resistance (Check for open):
      Tester Connection
      		Specified Condition
      HA1A (E68-1) - HA1A (E45-6)
      		Below 1 Ω
      HA2A (E65-1) - HA2A (E45-4)
      		Below 1 Ω
      Standard resistance (Check for short):
      Tester Connection
      		Specified Condition
      HA1A (E68-1) or HA1A (E45-6) - Body ground
      		10 kΩ or higher
      HA2A (E65-1) or HA2A (E45-4) - Body ground
      		10 kΩ or higher

    4. Reconnect the A/F sensor connector.

    5. Reconnect the ECM connector.

  1. Check the harness and the connector between the A/F sensor and A/F HTR relay.

    1. Disconnect the E68 or E65 A/F sensor connector.

    2. Remove the A/F HTR relay from the engine room No. 2 relay block.

    3. Measure the resistance.

      Standard resistance (Check for open):
      Tester Connection
      		Specified Condition
      +B (E68-2) - A/F HTR relay (3)
      		Below 1 Ω
      +B (E65-2) - A/F HTR relay (3)
      		Below 1 Ω
      Standard resistance (Check for short):
      Tester Connection
      		Specified Condition
      +B (E68-2) or A/F HTR relay (3) - Body ground
      		10 kΩ or higher
      +B (E65-2) or A/F HTR relay (3) - Body ground
      		10 kΩ or higher

    4. Reconnect the A/F sensor connector.

    5. Reinstall the A/F HTR relay.



NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK

REPLACE ECM