Sfi System Variable Resistor Circuit


DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK CO/HC

ADJUST CO CONCENTRATION

INSPECT VARIABLE RESISTOR

CHECK ECM (VAF VOLTAGE)

CHECK HARNESS AND CONNECTOR (VARIABLE RESISTOR - ECM)

SFI SYSTEM - Variable Resistor Circuit


DESCRIPTION

This resistor is used to change the air-fuel ratio of the air-fuel mixture.
The idle mixture is adjusted using this resistor.
Turning the idle mixture adjusting screw in the direction of the "R" on the variable resister moves the contacts inside the resistor, raising the terminal VAF voltage. Conversely, turning the screw in the direction of the "L" on the variable resister lowers the terminal VAF voltage.
When the terminal VAF voltage rises, the ECM increases the injection volume slightly, making the air-fuel mixture a little richer.

WIRING DIAGRAM


Toyota Fortuner. Ggn50, 60 Kun51, 61 Tgn51 Lan50.2Tr-Fe Engine Control System.Sfi System.Sfi System Variable Resistor Circuit


INSPECTION PROCEDURE

1.CHECK CO/HC
Toyota Fortuner. Ggn50, 60 Kun51, 61 Tgn51 Lan50.2Tr-Fe Engine Control System.Sfi System.Sfi System Variable Resistor Circuit

  1. Warm up the engine to normal operating temperature.

  1. Turn all accessories OFF.

  1. Connect all vacuum lines properly.

  1. Connect the tachometer.

  1. Check ignition timing correctly.

  1. Check idle speed correctly.

  1. Check that the CO meter is properly calibrated.

  1. Race the engine at 2,500 rpm for about 2 minutes.

  1. Insert a tester probe at least 40 cm (1.3 ft.) into the tailpipe.

  1. Measure the concentration within 1 to 3 minutes after racing the engine to allow the concentration to stabilize.

    Idle CO concentration:
    0.5 to 2.5%


OK
CHECK FOR PROBLEM SYMPTOMS TABLE
NG


2.ADJUST CO CONCENTRATION
Toyota Fortuner. Ggn50, 60 Kun51, 61 Tgn51 Lan50.2Tr-Fe Engine Control System.Sfi System.Sfi System Variable Resistor Circuit

  1. Put the vehicle in the same condition as the previous step (CHECK CO/HC).

  1. Using SST, adjust the idle mixture by turning the idle mixture adjusting screw in the variable resistor.

SST
09243-00020
Result
Result
Proceed
Concentration: 1.5 +-1%
B
Change in CO concentration
C
No change in CO concentration
A
HINT:
  1. Always check idle speed after turning the idle mixture adjusting screw. If it is incorrect, readjust idle speed.
  2. The idle mixture adjusting screw can be turned within 180°. Do not turn this screw more than specified.


B
ADJUSTMENT COMPLETE

C
CHECK CO/HC
A


3.INSPECT VARIABLE RESISTOR
Toyota Fortuner. Ggn50, 60 Kun51, 61 Tgn51 Lan50.2Tr-Fe Engine Control System.Sfi System.Sfi System Variable Resistor Circuit

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

    Standard resistance:
    Tester Connection
    		Specified Condition
    1 - 2
    		3.5 to 6.5 Ω

  1. While fully turning the idle mixture adjusting screw clockwise and counterclockwise using SST, measure the resistance.

SST
09243-00020
Standard resistance:
Tester Connection
Specified Condition
2 - 3
Resistance changes from approximately 5 to 0 kΩ


NG
REPLACE VARIABLE RESISTOR
OK


4.CHECK ECM (VAF VOLTAGE)
Toyota Fortuner. Ggn50, 60 Kun51, 61 Tgn51 Lan50.2Tr-Fe Engine Control System.Sfi System.Sfi System Variable Resistor Circuit

  1. Turn the ignition switch ON.

  1. While fully turning the idle mixture adjusting screw clockwise and counterclockwise slowly using SST, measure the voltage.

SST
09243-00020
Standard voltage:
Tester Connection
Specified Condition
E11-25 (VAF) - E11-28 (E2)
Voltage changes smoothly from 0 to approximately 5 V (does not change suddenly)


OK
REPLACE ECM
NG


5.CHECK HARNESS AND CONNECTOR (VARIABLE RESISTOR - ECM)
Toyota Fortuner. Ggn50, 60 Kun51, 61 Tgn51 Lan50.2Tr-Fe Engine Control System.Sfi System.Sfi System Variable Resistor Circuit

  1. Disconnect the V6 variable resistor connector.

  1. Disconnect the E11 ECM connector.

  1. Measure the resistance of the wire harness side connectors.

    Standard resistance:
    Tester Connection
    		Specified Condition
    V6-2 (VC) - E11-18 (VC)
    		Below 1 Ω
    V6-3 (VAF) - E11-25 (VAF)
    		Below 1 Ω
    V6-1 (E2) - E11-28 (E2)
    		Below 1 Ω
    V6-2 (VC) or E11-18 (VC) - Body ground
    		10 kΩ or higher
    V6-3 (VAF) or E11-25 (VAF) - Body ground
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE ECM