P0037

2AZ-FXE ENGINE CONTROL: SFI SYSTEM: P0037,P0038,P0141,P102D: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

DESCRIPTION

HINT
Bank 1 sensor 2 refers to the sensor mounted behind the three way catalytic converter and located far from the engine assembly.

A three way catalytic converter is used in order to convert the carbon monoxide, hydrocarbons, and nitrogen oxide, into less harmful substances. To allow the three way catalytic converter to function effectively, it is necessary to keep the air fuel ratio of the engine near the stoichiometric air fuel ratio. For the purpose of helping the hybrid vehicle control ECU to deliver accurate air fuel ratio control, a heated oxygen sensor is used.

The heated oxygen sensor is located behind the three way catalytic converter, and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low).

When the air fuel ratio becomes lean, the oxygen concentration in the exhaust gas is great. The heated oxygen sensor informs the hybrid vehicle control ECU that the post-three way catalytic converter air fuel ratio is lean (low voltage, i.e. less than 0.45 V).

Conversely, when the air fuel ratio is richer than the stoichiometric air fuel level, the oxygen concentration in the exhaust gas becomes small. The heated oxygen sensor informs the hybrid vehicle control ECU that the post-three way catalytic converter air fuel ratio is rich (high voltage, i.e. more than 0.45 V). The heated oxygen sensor has the property of changing its output voltage drastically when the air fuel ratio is close to the stoichiometric level.

The hybrid vehicle control ECU uses the supplementary information from the heated oxygen sensor to determine whether the air fuel ratio after the three way catalytic converter is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the heated oxygen sensor is working improperly due to internal malfunctions, the hybrid vehicle control ECU is unable to compensate for deviations in the primary air fuel ratio control.
HINT
- Sensor 2 refers to the sensor mounted behind the three-way catalytic converter and located far from the engine assembly.
- When any of these DTCs are set, the hybrid vehicle control ECU enters fail-safe mode. The hybrid vehicle control ECU turns off the heated oxygen sensor heater in fail-safe mode. Fail-safe mode continues until the power switch is turned off.
- The hybrid vehicle control ECU uses pulse width modulation to adjust the current through the heater. The heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.









HINT
- Bank 1 sensor 1 refers to the sensor closest to the engine assembly.
- Bank 1 sensor 2 refers to the sensor farthest away from the engine assembly.
MONITOR DESCRIPTION

The sensing portion of the heated oxygen 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 hybrid vehicle control ECU supplements the heat from the exhaust with heat from a heating element inside the sensor.

Heated Oxygen Sensor Heater Range Check (P0037, P0038 and P102D)

The hybrid vehicle control ECU monitors the current applied to the heated oxygen sensor heater to check the heater for malfunctions.

If the heater current is outside the normal range, the signal transmitted by the heated oxygen sensor becomes inaccurate. When the current in the heated oxygen sensor heater is outside the normal operating range, the hybrid vehicle control ECU interprets this as a malfunction in the sensor heater and stores a DTC.

Heated Oxygen Sensor Heater Performance (P0141)

After the accumulated heater ON time exceeds 100 seconds, the hybrid vehicle control ECU calculates the heater resistance using battery voltage and the current applied to the heater. If the resistance is above the threshold value, the hybrid vehicle control ECU determines that there is a malfunction in the heated oxygen sensor heater and stores DTC P0141.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

All





P0037 (Case 1)





P0037 (Case 2)





P0038





P0141 (Case 1)





P0141 (Case 2)





P102D





TYPICAL MALFUNCTION THRESHOLDS

P0037 (Case 1)





P0037 (Case 2)





P0038





P0141





P102D





COMPONENT OPERATING RANGE





MONITOR RESULT

- Refer to Checking Monitor Status Mode 6 Data.

CONFIRMATION DRIVING PATTERN





- Connect the Techstream to the DLC3.

- Turn the power switch on (IG) and turn the Techstream on.

- Clear the DTCs DTC Check / Clear.

- Turn the power switch off and wait for at least 30 seconds.

- Turn the power switch on (IG) and turn the Techstream on [A].

- Put the engine in inspection mode Component Tests and General Diagnostics.

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

- With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 2500 rpm for 1 minute [C].

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

- Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.

- Read the pending DTC [E].

HINT
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
- Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

- Input the DTC: P0037, P0038, P0141 or P102D.

- Check the DTC judgment result.





- If the judgment result shows INCOMPLETE or UNKNOWN, perform step [B] through [E] again.

WIRING DIAGRAM





INSPECTION PROCEDURE

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

HINT
Read freeze frame data using the Techstream. The hybrid vehicle control ECU 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.

PROCEDURE

1. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

(a) Disconnect the heated oxygen sensor connector.





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

Standard Resistance:





Text in Illustration





(c) Reconnect the heated oxygen sensor connector.

NG -- REPLACE HEATED OXYGEN SENSOR Removal
OK -- Continue to next step.

2. CHECK TERMINAL VOLTAGE (POWER SOURCE)

(a) Disconnect the heated oxygen sensor connector.





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

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

Standard Voltage:





Text in Illustration





(d) Reconnect the heated oxygen sensor connector.

NG -- INSPECT INTEGRATION RELAY (EFI MAIN RELAY)
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - HYBRID VEHICLE CONTROL ECU)

(a) Disconnect the heated oxygen sensor connector.

(b) Disconnect the hybrid vehicle control ECU 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 heated oxygen sensor connector.

(e) Reconnect the hybrid vehicle control ECU connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

4. CHECK WHETHER DTC OUTPUT RECURS (DTC P0037, P0038, P0141 OR P0102D)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Clear the DTCs DTC Check / Clear.

(e) Put the engine in inspection mode Component Tests and General Diagnostics.

(f) Start the engine.

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

(h) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.

(i) Read the pending DTCs.

Result:





B -- REPLACE HYBRID VEHICLE CONTROL ECU Removal

A -- CHECK FOR INTERMITTENT PROBLEMS

5. INSPECT INTEGRATION RELAY (EFI MAIN RELAY)

(a) Inspect the integration relay Inspection.

NG -- REPLACE INTEGRATION RELAY Removal
OK -- Continue to next step.

6. CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - HEATED OXYGEN SENSOR)

(a) Remove the integration relay from engine room relay block.

(b) Disconnect the integration relay connector.

(c) Disconnect the heated oxygen sensor connector.

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

Standard Resistance (Check for Open):





Standard Resistance (Check for Short):





(e) Reconnect the heated oxygen sensor connector.

(f) Reconnect the integration relay connector.

(g) Reinstall the integration relay.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

7. CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - IGCT RELAY) P0031

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

8. CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - BODY GROUND) P0031

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - EFI MAIN RELAY)