- DTC judgment completed
- System normal
Lexus NX: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2) (P0037,P0038,P0141,P102D)
Lexus NX Service Manual / Engine & Hybrid System / 2ar-fxe (engine Control) / Sfi System / Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2) (P0037,P0038,P0141,P102D)
DESCRIPTION
Refer to DTC P0136.
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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. Fail-safe mode continues until the power switch is turned off.
| DTC No. | Detection Item | DTC Detection Condition | Trouble Area | MIL | Memory |
|---|---|---|---|---|---|
| P0037 | Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2) | Heated oxygen sensor heater current is the specified value or less while the heater is operating (1 trip detection logic). |
| Comes on | DTC stored |
| P0038 | Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2) | The heater current is the specified value or higher while the heater is operating (1 trip detection logic). |
| Comes on | DTC stored |
| P0141 | Oxygen Sensor Heater Circuit (Bank 1 Sensor 2) | The cumulative heater resistance correction value exceeds the threshold (2 trip detection logic). |
| Comes on | DTC stored |
| P102D | O2 Sensor Heater Circuit Performance Bank 1 Sensor 2 Stuck ON | Heated oxygen sensor heater current is higher than the specified value while the heater is not operating (1 trip detection logic). | ECM | Comes on | DTC stored |
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 and P102D):-
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.
- After the accumulated heater on time exceeds 100 seconds, the ECM calculates the heater resistance using auxiliary 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.
MONITOR STRATEGY
| Related DTCs | P0037: Heated oxygen sensor (sensor 2) heater range check (low current) P0038: Heated oxygen sensor (sensor 2) heater range check (high current) P0141: Heated oxygen sensor (sensor 2) heater performance P102D: Heated oxygen sensor (sensor 2) heater performance |
| Required Sensors/Components (Main) | Heated oxygen sensor (sensor 2) heater |
| Required Sensors/Components (Related) | - |
| Frequency of Operation | Continuous: P0037, P0038, P102D Once per driving cycle: P0141 |
| Duration | 0.5 seconds: P0037, P102D Within 3 seconds: P0038 10 seconds: P0141 |
| MIL Operation | Immediate: P0037, P0038, P102D 2 driving cycles: P0141 |
| Sequence of Operation | None |
TYPICAL ENABLING CONDITIONS
All| Monitor runs whenever the following DTCs are not stored | None |
| All of the following conditions are met | - |
| Auxiliary battery voltage | 10.5 V or higher |
| Engine | Running |
| Starter | Off |
| Catalyst active air fuel ratio control | Not operating |
| Time after heater on | 10 seconds or more |
| Learned heater off current operation | Completed |
| Learned heater off current operation | Succeeded |
| Heated oxygen sensor heater high current fail (P0038) | Not detected |
| Command to heater output | On |
| All of the following conditions are met | - |
| Auxiliary battery voltage | 10.5 V or higher |
| Engine | Running |
| Starter | Off |
| Catalyst active air fuel ratio control | Not operating |
| Time after heater on | 10 seconds or more |
| Learned heater off current operation | Completed |
| Heater off current | Higher than 3.5 A |
| Heater current detected by heater monitor IC | 4 A or higher |
| Heated oxygen sensor heater high current fail (P0038) | Not detected |
| All of the following conditions are met | - |
| Auxiliary battery voltage | 10.5 V or higher |
| Engine | Running |
| Starter | Off |
| Catalyst active air fuel ratio control | Not operating |
| Time after heater on | 10 seconds or more |
| Learned heater off current operation | Completed |
| All of the following conditions are met | - |
| Heated oxygen sensor heater circuit fail (P0037, P0038, P102D) | Not detected |
| Auxiliary battery voltage | 10.5 V or higher |
| Fuel cut | Off |
| Time after fuel cut on to off | 30 seconds or more |
| Accumulated heater on time | 100 seconds or more |
| Learned heater off current operation | Completed |
| Duration that heated oxygen sensor impedance is less than 15 kΩ | 2 seconds or more |
| Active heater off control | Not operating |
| Active heater on control | Not operating |
| Command to heater output | On |
| All of the following conditions are met | - |
| Auxiliary battery voltage | 10.5 V or higher |
| Engine | Running |
| Starter | Off |
| Catalyst active air fuel ratio control | Not operating |
| Time after heater on | 10 seconds or more |
| Learned heater off current operation | Completed |
| Heater off current | Higher than 3.5 A |
| Heater current detected by heater monitor IC | 4 A or higher |
| Oxygen sensor heater low current fail (P0037) | Not detected |
| Oxygen sensor heater high current fail (P0038) | Not detected |
TYPICAL MALFUNCTION THRESHOLDS
P0037 (Case 1)| Heater on current - Learned heater off current | 0.15 A or less |
| Heater on current | 1 A or less |
| Both of the following conditions are met | - |
| Heater current detected by heater monitor IC | 4 A or higher |
| Command to heater output | On |
| Heater resistance | Varies with sensor element temperature (Example: Higher than 23 Ω) |
| Heater on current | Higher than 1 A |
MONITOR RESULT
Refer to detailed information in Checking Monitor Status.
Click here
| Monitor ID | Test ID | Scaling | Unit | Description |
|---|---|---|---|---|
| $42 | $91 | Multiply by 0.001 | Ohm | Oxygen sensor heater resistance bank 1 sensor 2 |
CONFIRMATION DRIVING PATTERN
- Connect the Techstream to the DLC3.
- Turn the power switch on (IG) and turn the Techstream on.
- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
- 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 (maintenance mode).
Click here
- 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].
HINT:
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, perform steps [C] and [D] after charging control has completed.
- 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, P0141 or P102D.
-
Check the DTC judgment result.
Techstream Display
Description
NORMAL
ABNORMAL
- DTC judgment completed
- System abnormal
INCOMPLETE
- DTC judgment not completed
- Perform driving pattern after confirming DTC enabling conditions
N/A
- Unable to perform DTC judgment
- Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit
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.
-
If no pending DTC is output, perform a universal trip and check for permanent DTCs.
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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 P0136.
Click here
CAUTION / NOTICE / HINT
NOTICE:
Inspect the fuses for circuits related to this system before performing the following procedure.
HINT:
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.
-
Refer to "Data List / Active Test" [O2 Heater B1S2 and O2 Heater Curr Val B1S2].
Click here
- When the value for the Data List item O2 Heater Curr Val B1S2 is not 0 A, the heater is on.
-
Change the fuel injection volume using the Control the Injection Volume for A/F Sensor function provided in the Active Test and monitor the heated oxygen sensor output voltage (Click here ). If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.
- 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) Inspect the heated oxygen sensor.
Click here
HINT:
Perform "Inspection After Repair" after replacing the heated oxygen sensor.
Click here
| NG | .gif) | REPLACE HEATED OXYGEN SENSOR |
|
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| 2. | CHECK TERMINAL VOLTAGE (POWER SOURCE OF HEATED OXYGEN SENSOR) |
| (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:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| C11-2 (+B) - Body ground | Power switch on (IG) | 11 to 14 V |
| NG | | GO TO STEP 5 |
|
| 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:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| C11-1 (HT1B) - C48-24 (HT1B) | Always | Below 1 Ω |
| C11-1 (HT1B) or C48-24 (HT1B) - Body ground | Always | 10 kΩ or higher |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 4. | CHECK WHETHER DTC OUTPUT RECURS (DTC P0037, P0038, P0141 OR P102D) |
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the Techstream on.
(d) Clear the DTCs.
Click here
(e) Turn the power switch off and wait for at least 30 seconds.
(f) Turn the power switch on (IG).
(g) Turn the Techstream on.
(h) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
(i) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(j) Read the pending DTCs.
Powertrain > Engine and ECT > Trouble Codes| Result | Proceed to |
|---|---|
| DTCs are not output | A |
| DTC P0037, P0038, P0141 or P102D is output | B |
| A | | CHECK FOR INTERMITTENT PROBLEMS |
| B | | REPLACE ECM |
| 5. | INSPECT EFI-MAIN NO. 2 RELAY |
(a) Inspect the EFI-MAIN No. 2 relay.
Click here
| NG | | REPLACE EFI-MAIN NO. 2 RELAY |
|
| 6. | CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 2 RELAY - HEATED OXYGEN SENSOR, EFI-MAIN RELAY) |
(a) Remove the EFI-MAIN NO. 2 relay from the No. 1 engine room relay block and junction block assembly.
(b) Remove the EFI-MAIN relay from the No. 1 engine room relay block and junction block assembly.
(c) Disconnect the heated oxygen sensor connector.
(d) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 3 (EFI-MAIN NO. 2 relay) - C11-2 (+B) | Always | Below 1 Ω |
| 1 (EFI-MAIN NO. 2 relay) - 3 (EFI-MAIN relay) | Always | Below 1 Ω |
| 2 (EFI-MAIN NO. 2 relay) - Body ground | Always | Below 1 Ω |
| 3 (EFI-MAIN NO. 2 relay) or C11-2 (+B) - Body ground | Always | 10 kΩ or higher |
| 1 (EFI-MAIN NO. 2 relay) or 3 (EFI-MAIN relay) - Body ground | Always | 10 kΩ or higher |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 7. | CHECK TERMINAL VOLTAGE (POWER SOURCE OF EFI-MAIN NO. 2 RELAY) |
| (a) Remove the EFI-MAIN NO. 2 relay from the No. 1 engine room relay block and junction block assembly. |
|
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(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 5 (EFI-MAIN NO. 2 relay) - Body ground | Always | 11 to 14 V |
| OK | | GO TO ECM POWER SOURCE CIRCUIT |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR (AUXILIARY BATTERY - EFI-MAIN NO. 2 RELAY) |
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