DTC P0031 P0032 P0051 P0052 1GR-FE

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

CHECK TERMINAL VOLTAGE (+B OF A/F SENSOR)

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

CHECK WHETHER DTC OUTPUT RECURS

INSPECT INTEGRATION NO.1 RELAY (A/F 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 DTC P0031

Refer to DTC P2195.

HINT:

1. When either of these DTCs are stored, 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 ignition switch is turned off.
2. Although the DTC titles say the oxygen sensor, these DTCs relate to the Air Fuel Ratio (A/F) sensor.
3. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
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.
   

DTC Code	DTC Detection Condition	Trouble Area
P0031 P0051	The Air Fuel ratio (A/F) sensor heater current is below 0.8 A (1 trip detection logic).	Open in Air Fuel Ratio (A/F) sensor heater circuit A/F sensor heater (for Bank 1, 2 Sensor 1) Integration relay (A/F relay) ECM
P0032 P0052	An Air Fuel ratio (A/F) sensor heater current failure (1 trip detection logic).	Short in A/F sensor heater circuit A/F sensor heater (for Bank 1, 2 Sensor 1) Integration relay (A/F relay) ECM

HINT:

1. Bank 1 refers to the bank that includes the No. 1 cylinder.
2. Bank 2 refers to the bank that does not include the No. 1 cylinder.
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 becomes inaccurate, as a result, the ECM is 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 stores a DTC.

Wiring diagram

Refer to DTC P2195.

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 AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

1. Disconnect the Air Fuel ratio (A/F) sensor connector.

2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance:

   for Bank 1 Sensor 1

   Tester Connection	Condition	Specified Condition
   1 (HA1A) - 2 (+B)	20°C (68°F)	1.8 to 3.4 ?
   1 (HA1A) - 4 (A1A-)	Always	10 k? or higher

   for Bank 2 Sensor 1

   Tester Connection	Condition	Specified Condition
   1 (HA2A) - 2 (+B)	20°C (68°F)	1.8 to 3.4 ?
   1 (HA2A) - 4 (A2A-)	Always	10 k? or higher

NG	REPLACE AIR FUEL RATIO SENSOR

OK

2.CHECK TERMINAL VOLTAGE (+B OF A/F SENSOR)

1. Measure the voltage according to the value(s) in the table below.

   Standard Voltage:

   for Bank 1 Sensor 1

   Tester Connection	Switch Condition	Specified Condition
   C22-2 (+B) - Body ground	Ignition switch ON	11 to 14 V

   for Bank 2 Sensor 1

   Tester Connection	Switch Condition	Specified Condition
   C23-2 (+B) - Body ground	Ignition switch ON	11 to 14 V

NG	Go to step 5

OK

3.CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)

1. Disconnect the ECM connector.

2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance (Check for Open):

   for LHD

   Tester Connection	Condition	Specified Condition
   C22-1 (HA1A) - C45-86 (HA1A)	Always	Below 1 ?
   C23-1 (HA2A) - C45-109 (HA2A)	Always	Below 1 ?

   for RHD

   Tester Connection	Condition	Specified Condition
   C22-1 (HA1A) - C46-86 (HA1A)	Always	Below 1 ?
   C23-1 (HA2A) - C46-109 (HA2A)	Always	Below 1 ?

   Standard Resistance (Check for Short):

   for LHD

   Tester Connection	Condition	Specified Condition
   C22-1 (HA1A) or C45-86 (HA1A) - Body ground	Always	10 k? or higher
   C23-1 (HA2A) or C45-109 (HA2A) - Body ground	Always	10 k? or higher

   for RHD

   Tester Connection	Condition	Specified Condition
   C22-1 (HA1A) or C46-86 (HA1A) - Body ground	Always	10 k? or higher
   C23-1 (HA2A) or C46-109 (HA2A) - Body ground	Always	10 k? or higher

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.CHECK WHETHER DTC OUTPUT RECURS

1. Connect the intelligent tester to the DLC3.

2. Turn the ignition switch to ON.

3. Turn the tester on.

4. Clear the DTCs.

5. Start the engine.

6. Allow the engine to idle for 1 minute or more.

7. Enter the following menus: Powertrain / Engine and ECT / DTC.

8. Read the DTCs.

Result

Result	Proceed to
No output	A
P0031, P0032, P0051 or P0052	B

B	REPLACE ECM

A
CHECK FOR INTERMITTENT PROBLEMS

5.INSPECT INTEGRATION NO.1 RELAY (A/F RELAY)

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

2. Inspect the A/F fuse.

   1. Remove the A/F fuse from the integration relay.

   2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance:

      Tester Connection	Condition	Specified Condition
      A/F fuse	Always	Below 1 ?

   3. Reinstall the A/F fuse.

3. Inspect the A/F relay.

   1. Measure the resistance according to the value(s) in the table below.

      Standard Resistance:

      Tester Connection	Condition	Specified Condition
      1A-4 - 1C-1	Battery voltage not applied to terminals 1A-2 and 1A-3	10 k? or higher
      	Battery voltage applied to terminals 1A-2 and 1A-3	Below 1 ?

NG	REPLACE INTEGRATION NO.1 RELAY

OK

6.CHECK HARNESS AND CONNECTOR (A/F SENSOR - INTEGRATION RELAY)

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

2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance (Check for Open):

   Tester Connection	Condition	Specified Condition
   C22-2 (+B) - 1A-4	Always	Below 1 ?
   C23-2 (+B) - 1A-4	Always	Below 1 ?

   Standard Resistance (Check for Short):

   Tester Connection	Condition	Specified Condition
   C22-2 (+B) or 1A-4 - Body ground	Always	10 k? or higher
   C23-2 (+B) or 1A-4 - Body ground	Always	10 k? or higher

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK
CHECK ECM POWER SOURCE CIRCUIT