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. Check any other dtcs output (in addition to dtc p0171 or p0172)

  5. Perform active test using intelligent tester (control the injection volume)

  6. Read value using intelligent tester (maf)

  7. Read value using intelligent tester (coolant temp)

  8. Check pcv hose connections

  9. Check air induction system

  10. Check for sparks and ignition

  11. Check for exhaust gas leak

  12. Check fuel pressure

  13. Inspect fuel injector assembly (injection and volume)

  14. Inspect heated oxygen sensor (heater resistance)

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

  16. Check harness and connector (heated oxygen sensor (sensor 1) - ecm)

  17. Replace heated oxygen sensor (sensor1)

  18. Perform confirmation driving pattern

  19. Check whether dtc output recurs (dtc p0171 or p0172)

DTC P0171 System Too Lean (Bank 1)

DTC P0172 System Too Rich (Bank 1)


​

DESCRIPTION

The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim includes the short-term fuel trim and the long-term fuel trim.
The short-term fuel trim is the short-term fuel compensation used to maintain the air-fuel ratio at the stoichiometric air-fuel ratio. The signal from the heated oxygen sensor indicates whether the air-fuel ratio is rich or lean compared to the stoichiometric air-fuel ratio. This variance triggers a reduction in the fuel volume if the air-fuel ratio is rich, and an increase in the fuel volume if it is lean.
The short-term fuel trim varies from the central value due to individual engine differences, wear over time and changes in the operating environment. The long-term fuel trim, which controls the overall fuel compensation, steadies long-term deviations of the short-term fuel trim from the central value.
If both the short-term fuel trim and the long-term fuel trim are lean or rich beyond a certain value, the ECM determines this as a malfunction, illuminates the MIL and sets a DTC.

DTC No.
DTC Detection Conditions
Trouble Areas
P0171
With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to lean side
(2 trip detection logic)
  1. Air induction system
  2. Injector blockage
  3. Mass Air Flow (MAF) meter
  4. Engine Coolant Temperature (ECT) sensor
  5. Fuel pressure
  6. Gas leakage from exhaust system
  7. Open or short in heated oxygen sensor (sensor 1) circuit
  8. Heated oxygen sensor (sensor 1)
  9. Heated oxygen sensor (sensor 1) heater
  10. Integration relay (EFI relay)
  11. PCV valve and hose
  12. PCV hose connections
  13. ECM
P0172
With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to rich side
(2 trip detection logic)
  1. Injector leakage or blockage
  2. MAF meter
  3. ECT sensor
  4. Ignition system
  5. Fuel pressure
  6. Gas leakage from exhaust system
  7. Open or short in heated oxygen sensor (sensor 1) circuit
  8. Heated oxygen sensor (sensor 1)
  9. Heated oxygen sensor (sensor 1) heater
  10. Integration relay (EFI relay)
  11. ECM
HINT:
  1. When DTC P0171 is recorded, the actual air-fuel ratio is on the lean side. When DTC P0172 is recorded, the actual air-fuel ratio is on the rich side.
  2. If the vehicle runs out of fuel, the air-fuel ratio is lean and DTC P0171 may be recorded. The MIL is then illuminated.
  3. When the total of the short-term and long-term fuel trim values is within 20 % (and ECT is more than 75°C (167°F)), the system is functioning normally.

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. A high heated oxygen sensor (sensor 1) voltage (0.5 V or more) indicates a rich air-fuel ratio.
  3. A low heated oxygen sensor (sensor 1) voltage (0.4 V or less) indicates a lean air-fuel ratio.
1.CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171 OR P0172)

  1. Connect an intelligent tester to the DLC3.

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

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

  1. Read DTCs.

Result:
Display (DTC Output)
Proceed To
P0171 or P0172
A
P0171 or P0172 and other DTCs
B
HINT:
If any DTCs other than P0171 or P0172 are output, troubleshoot those DTCs first.


Bnext
GO TO DTC CHART (Click here)
A
next down

2.PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME)

  1. Connect an intelligent tester to the DLC3.

  1. Start the engine and turn the tester on.

  1. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.

  1. Select the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

  1. Perform the Active Test Control with the intelligent tester and check the heated oxygen sensor status.

Standard voltage:
Heated oxygen sensor reacts in accordance with the increases and decreases in injection volume:
+25 % = RICH output: More than 0.5 V
-12.5 % = LEAN output: Less than 0.4 V
NOTICE:
The heated oxygen sensor (sensor 1) output has a few seconds of delay and the heated oxygen sensor (sensor 2) output has a maximum of 20 seconds of delay.

Case
Heated Oxygen Sensor (Sensor 1) Output Voltage
Heated Oxygen Sensor (Sensor 2) Output Voltage
Main Suspected Trouble Area
1
Heated oxygen sensor (Sensor 1) Yaris
Heated oxygen sensor (Sensor 1) Yaris
Heated oxygen sensor (Sensor 1) Yaris
Heated oxygen sensor (Sensor 1) Yaris
-
2
Heated oxygen sensor (Sensor 1) Yaris
Heated oxygen sensor (Sensor 1) Yaris
Heated oxygen sensor (Sensor 1) Yaris
Heated oxygen sensor (Sensor 1) Yaris
  1. Heated oxygen sensor (Sensor 1)
  2. Heated oxygen sensor heater (Sensor 1)
  3. Heated oxygen sensor circuit (Sensor 1)
3
Heated oxygen sensor (Sensor 2) Yaris
Heated oxygen sensor (Sensor 2) Yaris
Heated oxygen sensor (Sensor 2) Yaris
Heated oxygen sensor (Sensor 2) Yaris
  1. Heated oxygen sensor (Sensor 2)
  2. Heated oxygen sensor heater (Sensor 2)
  3. Heated oxygen sensor circuit (Sensor 2)
4
Injector Yaris
Injector Yaris
Injector Yaris
Injector Yaris
  1. Injector
  2. Fuel pressure
  3. Gas leak from exhaust system (Air-fuel ratio extremely RICH or LEAN)
Result:
Result
Proceed To
Case 1
C
Case 2
B
Case 3
A


Bnext
Go to step 11

Cnext
Go to step 15
A
next down

3.READ VALUE USING INTELLIGENT TESTER (MAF)

  1. Connect an intelligent tester to the DLC3.

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

  1. Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp and MAF.

  1. Allow the engine to idle until the Coolant Temp reaches 75°C (167°F) or more.

  1. Read the MAF with the engine in an idling condition and at an engine speed of 2,500 rpm.

    Standard:
    MAF while engine idling: 1 to 3 g/sec (shift position: N, A/C: OFF).
    MAF at engine speed of 2,500 rpm: 2 to 6 g/sec (shift position: N, A/C: OFF).


NGnext
REPLACE MASS AIR FLOW METER (Click here)
OK
next down

4.READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

  1. Connect the intelligent tester to the DLC3.

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

  1. Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp.

  1. Read the Coolant Temp twice, when the engine is both cold and warmed up.

    Standard:
    With cold engine: Same as ambient air temperature.
    With warm engine: 75°C to 100°C (167°F to 212°F).


NGnext
REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK
next down

5.CHECK PCV HOSE CONNECTIONS

  1. Check the PCV hose connections.

OK:
PCV hose is connected correctly and is not damaged.


NGnext
REPAIR OR REPLACE PCV HOSE
OK
next down

6.CHECK AIR INDUCTION SYSTEM

  1. Check the air induction system for vacuum leakage.

    OK:
    No leakage from air induction system.


NGnext
REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK
next down

7.CHECK FOR SPARKS AND IGNITION
Disconnect the injector connectors, in order to prevent the engine from starting. Yaris

  1. Disconnect the injector connectors, in order to prevent the engine from starting.

  1. Install the spark plug onto the ignition coil.

  1. Attach the spark plug assembly to the cylinder head.

  1. Crank the engine for less than 2 seconds and check the spark.

    OK:
    Sparks jump across electrode gap.

  1. Reconnect the injector connectors.



NGnext
REPAIR OR REPLACE IGNITION SYSTEM
OK
next down

8.CHECK FOR EXHAUST GAS LEAK

  1. Check for exhaust gas leakage.

    OK:
    No gas leakage.


NGnext
REPAIR OR REPLACE EXHAUST SYSTEM
OK
next down

9.CHECK FUEL PRESSURE

  1. Check the fuel pressure (Click here).

Standard:
304 to 343 kPa (3.1 to 3.5 kgf/cm2, 44.1 to 49.7 psi)


NGnext
REPAIR OR REPLACE FUEL SYSTEM
OK
next down

10.INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

  1. Check the injection volume (Click here).

    Standard:
    45 to 58 cm3(2.9 to 3.5 cu in.) per 15 seconds


NGnext
REPLACE FUEL INJECTOR ASSEMBLY (Click here)
OK
next down

11.INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
Disconnect the C36 HO2 sensor (sensor 1) connector. Yaris

  1. Disconnect the C36 HO2 sensor (sensor 1) connector.

  1. Check the resistance.

    Standard resistance:
    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

  1. Reconnect the HO2 sensor connector.



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

12.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
next down

13.CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR (SENSOR 1) - ECM)
Disconnect the C36 HO2 sensor connector. Yaris

Disconnect the C36 HO2 sensor connector. Yaris

  1. Disconnect the C36 HO2 sensor connector.

  1. Turn the ignition switch to ON.

  1. Measure the voltage between the +B terminal of the HO2 sensor connector and the body ground.

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

  1. Turn the ignition switch off.

  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
    OX1A (C36-3) - OX1A (C20-112)
    E2 (C36-4) - EX1A (C20-90)
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    HT1A (C36-1) or HT1A (C20-109) - Body ground
    		10 kΩ or higher
    OX1A (C36-3) or OX1A (C20-112) - Body ground
    E2 (C36-4) or EX1A- (C20-90) - Body ground

  1. Reconnect the ECM connector.

  1. Reconnect the HO2 sensor connector.



NGnext
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK
next down

14.REPLACE HEATED OXYGEN SENSOR (SENSOR1)

  1. Replace the heated oxygen sensor (sensor1)(Click here).


NEXT
next down

15.PERFORM CONFIRMATION DRIVING PATTERN

Connect an intelligent tester to the DLC3. Yaris

(a) Disconnect the negative battery cable for more than 1 minute to clear the air-fuel ratio learning value.
(b) Connect an intelligent tester to the DLC3.
(c) Turn the ignition switch to ON and turn the tester on.
(d) Switch the ECM from normal mode to check mode (Click here).
(e) Start the engine and let it idle until the engine coolant temperature is 75°C (167°F) or more.
(f) Allow the vehicle to run at 50 km/h (30 mph) or more for 3 minutes or more.
(g) Allow the engine to idle for approximately 2 minutes.
(h) Repeat steps (f) and (g) described above at least 3 times.
NOTICE:
If the conditions in this test are not strictly followed, malfunctions may not be detected.

NEXT
next down

16.CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

  1. Connect an intelligent tester to the DLC3.

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

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

  1. Read DTCs.

Result:
Display (DTC Output)
Proceed To
No output
A
P0171 or P0172
B


Bnext
Go to step 3
A
next down
END