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.

Click here

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).

  • Open in heated oxygen sensor (sensor 2) heater circuit
  • Heated oxygen sensor (sensor 2)
  • EFI-MAIN NO. 2 relay
  • ECM

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).

  • Short in heated oxygen sensor (sensor 2) heater circuit
  • Heated oxygen sensor (sensor 2)
  • EFI-MAIN NO. 2 relay
  • ECM

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).

  • Open or short in heated oxygen sensor (sensor 2) heater circuit
  • Heated oxygen sensor (sensor 2)
  • EFI-MAIN NO. 2 relay
  • ECM

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.

Heated Oxygen Sensor Heater Performance (P0141):

  • 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

P0037 (Case 1)

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

P0037 (Case 2)

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

P0038

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

P0141

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

P102D

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

P0037 (Case 2)

Heater on current

1 A or less

P0038

Both of the following conditions are met

-

Heater current detected by heater monitor IC

4 A or higher

Command to heater output

On

P0141

Heater resistance

Varies with sensor element temperature (Example: Higher than 23 Ω)

P102D

Heater on current

Higher than 1 A

MONITOR RESULT

Refer to detailed information in Checking Monitor Status.

Click here

P0141: O2 Sensor Heater / O2 HEATER B1S2

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

  1. Connect the Techstream to the DLC3.
  2. Turn the power switch on (IG) and turn the Techstream on.
  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
  4. Turn the power switch off and wait for at least 30 seconds.
  5. Turn the power switch on (IG) and turn the Techstream on [A].
  6. Put the engine in inspection mode (maintenance mode).

    Click here

  7. Start the engine and idle it for 5 minutes or more [B].
  8. 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.

  9. Idle the engine for 5 minutes or more [D].
  10. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
  11. 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.
  12. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
  13. Input the DTC: P0037, P0038, P0141 or P102D.
  14. Check the DTC judgment result.

    Techstream Display

    Description

    NORMAL

    • DTC judgment completed
    • System 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.
  15. If no pending DTC is output, perform a universal trip and check for permanent DTCs.

    Click here

    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

REPLACE HEATED OXYGEN SENSOR

OK

2.

CHECK TERMINAL VOLTAGE (POWER SOURCE OF HEATED OXYGEN SENSOR)

(a) Disconnect the heated oxygen sensor connector.

*a

Front view of wire harness connector

(to Heated Oxygen Sensor)

(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

OK

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

OK

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

Powertrain > Engine and ECT > Clear DTCs

(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

OK

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

OK

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.

*1

No. 1 Engine Room Relay Block and Junction Block Assembly

*2

EFI-MAIN NO. 2 Relay

(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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