P0037
1UR-FE ENGINE CONTROL: SFI SYSTEM: P0037,P0038,P0057,P0058,P0141,P0161,P102D,P105D: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
P105D - O2 Sensor Heater Circuit Performance Bank 2 Sensor 2 Stuck ON
DESCRIPTION
In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a Three-way Catalytic Converter (TWC) is used. For the most efficient use of the Three-way Catalytic Converter (TWC), the air-fuel ratio must be precisely controlled so that it is always close to 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 (TWC), and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with a 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 rich. The heated oxygen sensor informs the ECM that the post-Three-way Catalytic Converter (TWC) air-fuel ratio is lean (low voltage, i.e. below 0.45 V).
Conversely, when the air-fuel ratio is richer than the stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas becomes lean. The heated oxygen sensor informs the ECM that the post-Three-way Catalytic Converter (TWC) air-fuel ratio is rich (high voltage, i.e. higher 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 (TWC) 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
- When any of these DTCs are stored, the ECM enters fail-safe mode. The ECM turns off the heated oxygen sensor heater in fail-safe mode. The ECM continues operating in fail-safe mode 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.
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, P0058, P102D and P105D):
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 heater 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 determines that there is a malfunction in the heated oxygen sensor heater and stores DTC P0141 or P0161.
HINT
Normally, the heated oxygen sensor current is 0.4 to 1 A (when the engine is idling, the heated oxygen sensor is warmed up and battery voltage is 11 to 14 V).
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
P0037 and P0057 (Case 1)
P0037 and P0057 (Case 2)
P0038 and P0058
P0141 and P0161 (Case 1)
P0141 and P0161 (Case 2)
P102D and P105D
HINT
When the values for the Data List items O2 Heater Curr Val B1S2 and O2 Heater Curr Val B2S2 are not 0 A, the heater is on.
TYPICAL MALFUNCTION THRESHOLDS
P0037 and P0057 (Case 1)
P0037 and P0057 (Case 2)
P0038 and P0058
P0141 and P0161
P102D and P105D
COMPONENT OPERATING RANGE
MONITOR RESULT
Refer to Checking Monitor Status Mode 6 Data.
CONFIRMATION DRIVING PATTERN
- Connect the Techstream to the DLC3.
- Turn the engine switch on (IG) and turn the Techstream on.
- Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
- Turn the engine switch off and wait for at least 30 seconds.
- 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 and ECT / Trouble Codes [E].
- Read the pending DTCs.
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, P0057, P0058, P0141, P0161, P102D or P105D.
- 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 UNKNOWN, perform steps [B] through [E] again.
- If 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 of circuits related to this system before performing the following inspection procedure.
HINT
- Sensor 2 refers to the sensor mounted behind the Three-way Catalytic Converter (TWC) and located far from the engine assembly.
- Read freeze frame data using the Techstream. 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.
- Refer to "Data List / Active Test" [O2 Heater B1S2, O2 Heater B2S2, O2 Heater Curr Val B1S2 and O2 Heater Curr Val B2S2] Data List / Active Test.
- 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.
PROCEDURE
1. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
(a) Inspect the heated oxygen sensor Heated Oxygen Sensor.
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
NG -- INSPECT NO. 1 INTEGRATION RELAY (EFI)
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:
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. CHECK WHETHER DTC OUTPUT RECURS
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Clear DTCs DTC Check / Clear.
(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
5. INSPECT NO. 1 INTEGRATION RELAY (EFI)
(a) Inspect the No. 1 integration relay (EFI) Testing and Inspection.
NG -- REPLACE NO. 1 INTEGRATION RELAY (EFI)
OK -- Continue to next step.
6. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - NO. 1 INTEGRATION RELAY)
(a) Disconnect the heated oxygen sensor connector.
(b) Remove the No. 1 integration relay from the engine room relay block.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- CHECK ECM POWER SOURCE CIRCUIT