P0031

2GR-FSE ENGINE CONTROL: SFI SYSTEM: P0031, P0032, P0051, P0052: Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
P0052 - Oxygen (A/F) Sensor Heater Control Circuit High (Bank 2 Sensor 1)

DESCRIPTION

HINT
Although the DTC titles include oxygen sensor, these DTCs relate to the air fuel ratio sensor.

The air fuel ratio sensor generates voltage* that corresponds to the actual air fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air fuel ratio. The ECM determines the deviation from the stoichiometric air fuel ratio level, and regulates the fuel injection time. If the air fuel ratio sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.

The air fuel ratio sensor is the planar type and is integrated with a heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore the sensor activation is accelerated.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxide (NOx) components in the exhaust gas, a three way catalytic converter is used. For the most efficient use of the three way catalytic converter, the air fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.

*: Value changes inside the ECM. Since the air fuel ratio sensor is a current output element, the current is converted to a voltage inside the ECM. Any measurements taken at the air fuel ratio sensor or ECM connectors will show a constant voltage.





HINT
- When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio sensor heater in fail-safe mode. Fail-safe mode continues until the engine switch is turned off.
- The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The air fuel ratio sensor heater circuit uses a relay on the +B side of the circuit.










MONITOR DESCRIPTION

- The ECM uses information from the air fuel ratio 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 to purify the exhaust gases.

- The air fuel ratio 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 air fuel ratio 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 air fuel ratio sensor will be inaccurate, as a result, the ECM will be unable to regulate air fuel ratio properly.

- When the current in the air fuel ratio sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and sets a DTC.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

All





P0031 and P0051





P0032 and P0052





TYPICAL MALFUNCTION THRESHOLDS

P0031 and P0051





P0032 and P0052





COMPONENT OPERATING RANGE

P0031 and P0051





P0032 and P0052





CONFIRMATION DRIVING PATTERN





1. Connect the Techstream to the DLC3.

2. Turn the engine switch on (IG) and turn the Techstream on.

3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) Reading and Clearing Diagnostic Trouble Codes.

4. Turn the engine switch off and wait for 30 seconds.

5. Turn the engine switch on (IG) and turn the Techstream on [A].

6. Start the engine and idle it for 5 minutes or more [B].

7. With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 3000 rpm for 1 minute [C].

8. Idle the engine for 5 minutes or more [D].

9. Enter the following menus: Powertrain / Engine / Trouble Codes [E].

10. Read Pending DTCs.

HINT
- If a pending DTC is not output, perform the following procedure.
- If a pending DTC is output, the system is malfunctioning.

11. Enter the following menus: Powertrain / Engine / Utility / All Readiness.

12. Input the DTC: P0031, P0032, P0051 or P0052.

13. Check the DTC judgment result.





HINT
- If the judgment result shows NORMAL, the system is normal.
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows INCOMPLETE or N/A, perform steps [B] through [E] again.

14. If no pending DTC is output, perform a universal trip and check for permanent DTCs Reading and Clearing Diagnostic Trouble Codes.

HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

Refer to DTC P2195 P2195.

INSPECTION PROCEDURE

NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.

HINT
- Refer to "Data List / Active Test" [A/F Heater Duty #1 and A/F Heater Duty #2] Data List / Active List.
- Bank 1 refers to the bank that includes the No. 1 cylinder*.
*: The No. 1 cylinder is the cylinder which is farthest from the transmission.
- Bank 2 refers to the bank that does not include the No. 1 cylinder.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.
- Read freeze frame data using the Techstream. 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.
- Change the fuel injection volume using the Control the Injection Volume function provided in the Active Test and monitor the air fuel ratio sensor output voltage P0136. If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

PROCEDURE

1. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

(a) Inspect the air fuel ratio sensor Air Fuel Ratio Sensor.

NG -- REPLACE AIR FUEL RATIO SENSOR Removal
OK -- Continue to next step.

2. CHECK TERMINAL VOLTAGE (+B OF AIR FUEL RATIO SENSOR)

(a) Disconnect the air fuel ratio sensor connector.





(b) Turn the engine switch on (IG).

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

Standard Voltage:





Text in Illustration





(d) Reconnect the air fuel ratio sensor connector.

NG -- INSPECT RELAY (A/F RELAY)
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)

(a) Disconnect the air fuel ratio sensor connector.

(b) Disconnect the ECM connector.

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

Standard Resistance (Check for Open):





Standard Resistance (Check for Short):





(d) Reconnect the air fuel ratio sensor connector.

(e) Reconnect the ECM connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - ECM)
OK -- Continue to next step.

4. CHECK WHETHER DTC OUTPUT RECURS (DTC P0031, P0032, P0051 OR P0052)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.

(e) Start the engine.

(f) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

(g) Read the output pending DTCs using the Techstream.

Result:





B -- REPLACE ECM Removal

A -- CHECK FOR INTERMITTENT PROBLEMS Check for Intermittent Problems

5. INSPECT RELAY (A/F RELAY)

(a) Remove the A/F relay from the engine room relay block No. 2.





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

Standard Resistance:





(c) Reinstall the A/F relay.

NG -- REPLACE RELAY (A/F RELAY)
OK -- Continue to next step.

6. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - A/F RELAY)

(a) Disconnect the air fuel ratio sensor connector.

(b) Remove the A/F relay from engine room relay block No. 2.

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

Standard Resistance (Check for Open):





Standard Resistance (Check for Short):





(d) Reinstall the A/F relay.

(e) Reconnect the air fuel ratio sensor connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - A/F RELAY)
OK -- Continue to next step.

7. CHECK TERMINAL VOLTAGE (A/F RELAY)

(a) Remove the A/F relay from engine room relay block No. 2.





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

Standard Voltage:





Text in Illustration





(c) Reinstall the A/F relay.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - A/F RELAY)
OK -- Continue to next step.

8. CHECK HARNESS AND CONNECTOR (A/F RELAY - BODY GROUND)

(a) Remove the A/F relay from engine room relay block No. 2.





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

Standard Resistance (Check for Open):





Text in Illustration





(c) Reinstall the A/F relay.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (A/F RELAY - BODY GROUND)

OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (EFI MAIN RELAY - A/F RELAY)