Up to 08/2009

2GR-FE ENGINE CONTROL: SFI SYSTEM: P0037,P0038,P0057,P0058,P0141,P0161: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
P0161 - Oxygen Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

DESCRIPTION

A three-way catalytic converter is used in order to convert the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) 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 ECM 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 becomes rich. The heated oxygen sensor informs the ECM 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 lean. The heated oxygen sensor informs the ECM 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 ECM 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 ECM 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 ECM enters fail-safe mode. The ECM turns off the heated oxygen 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 heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.









HINT
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that does not include cylinder No. 1.
- Sensor 1 refers to the sensor closest to the engine assembly.
- 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 ECM supplements the heat from the exhaust with heat from a heating element inside the sensor.

Heated oxygen sensor heater range check (P0037, P0038, P0057 and P0058):

The ECM 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 ECM interprets this as a malfunction in the sensor and stores a DTC.

Heated oxygen sensor heater performance (P0141 and P0161):

After the accumulated heater on time exceeds 100 seconds, the ECM calculates the heater resistance using the battery voltage and the current applied to the heater. If the resistance is above the threshold value, the ECM will determine that there is a malfunction in the heated oxygen sensor heater and set DTCs P0141 and P0161.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

All





P0037 and P0057 (Case 1)





P0037 and P0057 (Case 2)





P0038 and P0058 (Case 1)





P0038 and P0058 (Case 2)





P0141 and P0161





TYPICAL MALFUNCTION THRESHOLDS

P0037 and P0057





P0038 and P0058





P0141 and P0161





COMPONENT OPERATING RANGE





CONFIRMATION DRIVING PATTERN





- Connect the Techstream to the DLC3.

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

- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) DTC Check / Clear.

- Turn the engine switch off.

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

- 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 3000 rpm for 1 minute [C].

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

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

- Input the DTC: P0037, P0038, P0057, P0058, P0141, or P0161.

- Check the DTC judgment result [E].





HINT
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows INCOMPLETE or UNKNOWN, perform steps [B] through [E] again.
- If the test result is UNKNOWN, enter the following menus: Powertrain / Engine / Trouble Codes / Pending.

- Read Pending DTCs.

HINT
If a pending DTC is output, the system is malfunctioning.

- If the test result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs DTC Check / Clear.

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

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 (+B OF HEATED OXYGEN SENSOR)

(a) Disconnect the heated oxygen 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 heated oxygen sensor connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (HEATED OXYGEN SENSOR - EFI MAIN RELAY)
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)

(a) Disconnect the heated oxygen 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):





Text in Illustration





(d) Reconnect the heated oxygen sensor connector.

(e) Reconnect the ECM connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (HEATED OXYGEN SENSOR - ECM)

OK -- REPLACE ECM Removal