SFI SYSTEM, Diagnostic DTC:P0037, P0038, P102D

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 primary air-fuel ratio control.

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.

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

CONFIRMATION DRIVING PATTERN

1. Connect the intelligent tester to the DLC3.

2. Turn the ignition switch to ON and turn the tester on.

3. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).

4. Turn the ignition switch off and wait for at least 30 seconds.

5. Turn the ignition switch to ON and turn the tester on [A].

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

7. With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 3000 rpm for 1 minute [C].

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

9. Enter the following menus: Powertrain / Engine and ECT / DTC [E].

10. Read pending DTCs.

    Tech Tips

    
    

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

    • If a pending DTC is not output, perform the following procedure.

11. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

12. Input the DTC: P0037, P0038 or P102D.

13. Check the DTC judgment result.

    Tester 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

    Tech Tips

    
    

    • 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.

WIRING DIAGRAM

Refer to DTC P0031 Click here.

CAUTION / NOTICE / HINT

PROCEDURE

1. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

   
   

   1. Inspect the heated oxygen sensor Click here.

   
   

   NG

   REPLACE HEATED OXYGEN SENSOR Click here

   OK

2. CHECK TERMINAL VOLTAGE (POWER SOURCE)

   
   
   1. 

      Text in Illustration

      *a	Front view of wire harness connector (to Heated Oxygen Sensor)

      Disconnect the heated oxygen sensor connector.

   2. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition B95-2 (+B) - Body ground Ignition switch ON 11 to 14 V

   
   

   NG

   INSPECT NO. 1 INTEGRATION RELAY (EFI MAIN) Click here

   OK

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

   
   

   1. Disconnect the heated oxygen sensor connector.

   2. Disconnect the ECM connector.

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

      Standard Resistance
      for LHD Tester Connection Condition Specified Condition B95-1 (HT1B) - B22-22 (HT1B) Always Below 1 Ω B95-1 (HT1B) or B22-22 (HT1B) - Body ground Always 10 kΩ or higher
      for RHD Tester Connection Condition Specified Condition B95-1 (HT1B) - B23-22 (HT1B) Always Below 1 Ω B95-1 (HT1B) or B23-22 (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 OR P102D)

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Turn the ignition switch to ON.

   3. Turn the tester on.

   4. Clear the DTCs Click here.

   5. Turn the ignition switch off and wait for at least 30 seconds.

   6. Turn the ignition switch to ON.

   7. Turn the tester on.

   8. Start the engine.

   9. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

   10. Enter the following menus: Powertrain / Engine and ECT / DTC.

   11. Read DTCs.

       Result

       Result	Proceed to
       DTC is not output	A
       DTC P0037, P0038 or P102D is output	B

   
   

   A

   CHECK FOR INTERMITTENT PROBLEMS Click here

   B

   REPLACE ECM Click here

5. INSPECT NO. 1 INTEGRATION RELAY (EFI MAIN)

   
   

   1. Inspect the No. 1 integration relay (EFI MAIN) Click here.

   
   

   NG

   REPLACE NO. 1 INTEGRATION RELAY Click here

   OK

6. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - NO. 1 INTEGRATION RELAY)

   
   

   1. Disconnect the heated oxygen sensor connector.

   2. Remove the No. 1 integration relay from the engine room relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition B95-2 (+B) - 1E-4 Always Below 1 Ω B95-2 (+B) or 1E-4 - Body ground Always 10 kΩ or higher

   
   

   OK

   CHECK ECM POWER SOURCE CIRCUIT Click here

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR