Sfi System Cranking Holding Function Circuit

Engine. Lexus Gs430, Gs300. Uzs190 Grs190
3Uz-Fe Engine Control System. Lexus Gs430, Gs300. Uzs190 Grs190

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK OPERATION OF ENGINE CRANKING

READ DATA LIST (STARTER SIGNAL)

CHECK ECM (STSW AND STAR VOLTAGE)

INSPECT RELAY (Marking: ST CUT)

INSPECT PARK / NEUTRAL POSITION SWITCH

INSPECT RELAY (Marking: STARTER)

CHECK WIRE HARNESS (PARK / NEUTRAL POSITION SWITCH - STARTER RELAY)

INSPECT ENGINE ROOM RELAY BLOCK (STARTER RELAY VOLTAGE)

INSPECT STARTER

CHECK WIRE HARNESS (ECM - POWER SOURCE CONTROL ECU)

SFI SYSTEM - Cranking Holding Function Circuit


DESCRIPTION

The cranking holding control system provides current to the starter when the ECM detects the engine switch's start signal (STSW). When the ECM performs a firing judgment, the system cuts current to the starter. When an ECM receives the STSW signal, it turns on the ST CUT relay, which prevents flickering of the combination meter, clock, audio system, etc. Also, the ECM sends a signal to the ECM's STAR terminal. Then the STAR output signal travels through the park/neutral position (PNP) switch to the STARTER relay, causing the starter to activate.
When the engine is cranking, the starter operation signal is sent to the ECM's STA terminal.

Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit


WIRING DIAGRAM


Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit


Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit


INSPECTION PROCEDURE

1.CHECK OPERATION OF ENGINE CRANKING

  1. When turning the engine switch to start, check whether the starter motor starts.



OK
CHECK FOR INTERMITTENT PROBLEMS
NG


2.READ DATA LIST (STARTER SIGNAL)

  1. Connect the intelligent tester to the DLC3.

  1. Enter the following menu: Powertrain / Engine / Data List / Primary / Starter Signal.

  1. Confirm the starter signal status when the engine switch is operated.

    OK:
    Engine Switch Position
    		Starter Signal
    On (IG)
    		OFF
    Start
    		ON


OK
Go to step 6
NG


3.CHECK ECM (STSW AND STAR VOLTAGE)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit

  1. Measure the voltage of the A6 and E7 ECM connectors.

    Standard voltage:
    Tester Connection
    		Specified Condition
    A6-19 (STSW) - E7-7 (E1)
    		9 to 14 V
    E7-4 (STAR) - E7-7 (E1)
    		9 to 14 V

Result:

Terminal STSW
Terminal STAR
Proceed to
9 to 14 V
9 to 14 V
A
9 to 14 V
0 V
B
0 V
0 V
C


B
REPLACE ECM

C
Go to step 10
A


4.INSPECT RELAY (Marking: ST CUT)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit

  1. Remove the starter cut relay from engine room No. 2 relay block.

  1. Measure the resistance of the relay.

    Standard resistance:
    Tester Connection
    		Specified Condition
    3-5
    		10 kΩ or higher
    3-5
    		Below 1 Ω
    (when battery voltage is applied to terminals 1 and 2)


NG
REPLACE RELAY
OK


5.INSPECT PARK / NEUTRAL POSITION SWITCH
Lexus Gs430, Gs300. Uzs190 Grs190

  1. Move the shift lever to the P or N position.

  1. Disconnect the E25 PNP switch connector.

  1. Measure the resistance of the PNP switch.

    Standard resistance:
    Shift Position
    		Tester Connection
    		Specified Condition
    P or N
    		9 - 6
    		Below 1 Ω


NG
REPLACE PARK / NEUTRAL POSITION SWITCH
OK

REPAIR OR REPLACE HARNESS AND CONNECTOR (PARK / NEUTRAL POSITION SWITCH - ECM, ECM - ST CUT RELAY, ST CUT RELAY - PARK / NEUTRAL POSITION SWITCH)

6.INSPECT RELAY (Marking: STARTER)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit

  1. Remove the starter relay from engine room No. 1 relay block.

  1. Measure the resistance of the relay.

    Standard resistance:
    Tester Connection
    		Specified Condition
    3 - 5
    		10 kΩ or higher
    3 - 5
    		Below 1 Ω
    (when battery voltage is applied to terminals 1 and 2)


NG
REPLACE RELAY
OK


7.CHECK WIRE HARNESS (PARK / NEUTRAL POSITION SWITCH - STARTER RELAY)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit

  1. Check the wire harness between the PNP switch and starter relay.

    1. Disconnect the E25 PNP switch connector.

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

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

      Standard resistance:
      Tester Connection
      		Specified Condition
      E25-6 (PNP switch) - Relay block STARTER relay terminal 1
      		Below 1 Ω
      E25-6 (PNP switch) - Relay block STARTER relay terminal 1 - Body ground
      		10 kΩ or higher

  1. Check the wire harness between the starter relay and body ground.

    1. Remove the starter relay from the engine room No. 1 relay block.

    2. Measure the resistance of the wire harness side connector.

      Standard resistance:
      Tester Connection
      		Specified Condition
      Relay block STARTER relay terminal 2 - Body ground
      		Below 1 Ω


NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK


8.INSPECT ENGINE ROOM RELAY BLOCK (STARTER RELAY VOLTAGE)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit

  1. Remove the starter relay from the engine room No. 1 relay block.

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

    Standard voltage:
    Tester Connection
    		Specified Condition
    Relay block STARTER relay terminal 5 - Body ground
    		9 to 14 V


NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK


9.INSPECT STARTER

  1. Inspect the starter (Click here).



NG
REPAIR OR REPLACE STARTER
OK

REPAIR OR REPLACE HARNESS AND CONNECTOR (STARTER RELAY - STARTER, STARTER - BATTERY)

10.CHECK WIRE HARNESS (ECM - POWER SOURCE CONTROL ECU)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System.Sfi System Cranking Holding Function Circuit

  1. Disconnect the A6 ECM connector.

  1. Disconnect the L73 ECU connector.

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

    Standard resistance:
    Tester Connection
    		Specified Condition
    A6-19 (STSW) - L73-39 (STSW)
    		Below 1 Ω
    A6-19 (STSW) or L73-39 (STSW) - Body ground
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK

INSPECT STARTING SYSTEM