Brand:

Toyota

Model Name:

Yaris NCP90 91 92 93

Manual:

Repair Manual

Section:

1Nz-Fe Engine Control System

Title:

Sfi System

  1. Description

  2. Wiring diagram

  3. Inspection procedure

  4. Inspect heated oxygen sensor (heater resistance)

  5. Check terminal voltage (+b of ho2 sensor)

  6. Inspect integration no.1 relay (efi relay)

  7. Check harness and connector (ho2 sensor - efi relay)

  8. Check harness and connector (ho2 sensor - ecm)

  9. Check whether dtc output recurs (dtc p0031, p0032, p0037 or p0038)

DTC P0031 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

DTC P0032 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 1)

DTC P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

DTC P0038 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2)

HINT:
  1. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
  2. Sensor 2 refers to the sensor mounted behind the TWC and located far from the engine assembly.

DESCRIPTION

The Heated Oxygen (HO2) sensor is used to monitor the oxygen concentration in the exhaust gas. For optimum catalytic converter operation, the air-fuel mixture must be maintained near the ideal stoichiometric air-fuel ratio. The HO2 sensor output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. The ECM adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2 sensor generates a voltage between 0.1 and 0.9 V in response to the oxygen concentration in the exhaust gas.
If the oxygen concentration in the exhaust gas increases, the air-fuel ratio is described as LEAN. The HO2 sensor voltage drops to below 0.45 V and the HO2 sensor informs the ECM of the LEAN condition. If there is little oxygen in the exhaust gas, the air-fuel ratio is described as RICH. The HO2 sensor voltage increases to above 0.45 V and the HO2 sensor informs the ECM of the RICH condition.
If there is little oxygen in the exhaust gas, the air-fuel ratio is described as RICH. The heated oxygen sensor voltage increases to above 0.45 V and the heated oxygen sensor informs the ECM of the RICH condition.

Open in HO2 sensor heater circuit Yaris

HINT:
The ECM has 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.

Open in HO2 sensor heater circuit Yaris


DTC No.
DTC Detection Conditions
Trouble Areas
P0031
P0037
Heated Oxygen (HO2) sensor heater current below 0.25 A when heater operates with +B greater than 10.5 V
(1 trip detection logic)
  1. Open in HO2 sensor heater circuit
  2. HO2 sensor heater
  3. Integration relay (EFI relay)
  4. ECM
P0032
P0038
HO2 sensor heater current exceeds 2 A when heater operates
(1 trip detection logic)
  1. Short in HO2 sensor heater circuit
  2. HO2 sensor heater
  3. Integration relay (EFI relay)
  4. ECM

WIRING DIAGRAM


Read freeze frame data using an intelligent tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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. Yaris


INSPECTION PROCEDURE

HINT:
  1. Read freeze frame data using an intelligent tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.
  2. Sensor 1 refers to the sensor closest to the engine body.
  3. Sensor 2 refers to the sensor farthest away from the engine body.
1.INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
Disconnect the C36 or D28 Heated Oxygen (HO2) sensor connector. Yaris

  1. Disconnect the C36 or D28 Heated Oxygen (HO2) sensor connector.

  1. Measure the resistance between the terminals of the HO2 sensor connector.

    Standard resistance (Sensor 1):
    Tester Connections
    		Specified Conditions
    HT1A (1) - +B (2)
    		5.3 to 7.5 Ω at 20°C (68°F)
    HT1A (1) - E2 (4)
    		10 kΩ or higher
    Standard resistance (Sensor 2):
    Tester Connections
    		Specified Conditions
    HT1B (1) - +B (2)
    		11 to 16 Ω at 20°C (68°F)
    HT1B (1) - E2 (4)
    		10 kΩ or higher

  1. Reconnect the HO2 sensor connectors.



NGnext
REPLACE HEATED OXYGEN SENSOR (Click here)
OK
next down

2.CHECK TERMINAL VOLTAGE (+B OF HO2 SENSOR)
  1. Disconnect the C36 or D28 HO2 sensor connector. Yaris

  2. Disconnect the C36 or D28 HO2 sensor connector.

  1. Turn the ignition switch to ON.

  1. Measure the voltage between the terminals of the C36 or D28 HO2 sensor connector and the body ground.

    Standard voltage:
    Tester Connections
    		Specified Conditions
    +B (C36-2) - Body ground
    		9 to 14 V
    +B (D28-2) - Body ground

  1. Reconnect the HO2 sensor connector.



OKnext
Go to step 5
NG
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3.INSPECT INTEGRATION NO.1 RELAY (EFI RELAY)
Remove the integration relay from the engine room relay block. Yaris

  1. Remove the integration relay from the engine room relay block.

  1. Inspect the EFI fuse.

    1. Remove the EFI fuse from the integration relay.

    2. Check the EFI fuse resistance.

      Standard resistance:
      Below 1 Ω

    3. Reinstall the EFI fuse.

  1. Inspect the EFI relay.

    1. Check the EFI relay resistance.

      Standard resistance:
      Tester Connections
      		Specified Conditions
      1C-1 - 1A-4
      		10 kΩ or higher
      Below 1 Ω
      (Apply battery voltage between terminals 1A-2 and 1A-3)

  1. Reinstall the integration relay.



NGnext
REPLACE INTEGRATION NO.1 RELAY
OK
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4.CHECK HARNESS AND CONNECTOR (HO2 SENSOR - EFI RELAY)
Disconnect the C36 or D28 HO2 sensor connector. Yaris

  1. Disconnect the C36 or D28 HO2 sensor connector.

  1. Remove the integration relay from the engine room relay block.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    +B (C36-2) - Engine room relay block (1A-4)
    		Below 1 Ω
    +B (D28-2) - Engine room relay block (1A-4)
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    +B (C36-2) or Engine room relay block (1A-4) - Body ground
    		10 kΩ or higher
    +B (D28-2) or Engine room relay block (1A-4) - Body ground

  1. Reconnect the HO2 sensor connector.

  1. Reinstall the integration relay.



NGnext
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK
next down
CHECK ECM POWER SOURCE CIRCUIT (Click here)

5.CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM)
Disconnect the C36 or D28 HO2 sensor connector. Yaris

  1. Disconnect the C36 or D28 HO2 sensor connector.

  1. Disconnect the C20 ECM connector.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    HT1A (C36-1) - HT1A (C20-109)
    		Below 1 Ω
    HT1B (D28-1) - HT1B (C20-47)
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    HT1A (C36-1) or HT1A (C20-109) - Body ground
    		10 kΩ or higher
    HT1B (D28-1) or HT1B (C20-47) - Body ground

  1. Reconnect the HO2 sensor connector.

  1. Reconnect the ECM connector.



NGnext
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK
next down

6.CHECK WHETHER DTC OUTPUT RECURS (DTC P0031, P0032, P0037 OR P0038)

  1. Connect an intelligent tester to the DLC3.

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

  1. Clear DTCs (Click here).

  1. Start the engine.

  1. Allow the engine to idle for 1 minute or more.

  1. Select the following menu items: Powertrain / Engine and ECT / DTC.

  1. Read DTCs.

    Result:
    Display (DTC Output)
    		Proceed To
    No output
    		A
    P0031, P0032, P0037 or P0038
    		B


Bnext
REPLACE ECM (Click here)
A
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CHECK FOR INTERMITTENT PROBLEMS (Click here)