Combustion Type Power Heater System Power Heater Fuel Pump Circuit

Heater & Air Conditioning System. Lexus Is250, Is220D. Gse20 Ale20
Heater. Lexus Is250, Is220D. Gse20 Ale20

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK HARNESS AND CONNECTOR (COMBUSTION HEATER ASSEMBLY - HEATER FUEL PUMP)

CHECK HARNESS AND CONNECTOR (HEATER FUEL PUMP - BODY GROUND)

INSPECT HEATER FUEL PUMP

INSPECT POWER HEATER ECU (COMBUSTION HEATER ASSEMBLY)

COMBUSTION TYPE POWER HEATER SYSTEM - Power Heater Fuel Pump Circuit


DESCRIPTION

When the power heater switch is turned on, the heater fuel pump receives a drive voltage from the power heater ECU (combustion heater assembly). The heater fuel pump provides the combustion heater assembly with fuel necessary for combustion, allowing the combustion heater assembly to operate.

WIRING DIAGRAM


Lexus Is250, Is220D. Gse20 Ale20.Heater.Combustion Type Power Heater System.Combustion Type Power Heater System Power Heater Fuel Pump Circuit


INSPECTION PROCEDURE

1.CHECK HARNESS AND CONNECTOR (COMBUSTION HEATER ASSEMBLY - HEATER FUEL PUMP)


    Lexus Is250, Is220D. Gse20 Ale20.Heater.Combustion Type Power Heater System.Combustion Type Power Heater System Power Heater Fuel Pump Circuit

  1. Disconnect the connector from the power heater ECU (combustion heater assembly).

  1. Disconnect the connector from the heater fuel pump.

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

    Standard resistance:
    Tester connection
    (Symbols)
    		Condition
    		Specified condition
    A51-2 (L) - Q55-2
    		Always
    		Below 1 Ω
    A51-2 (L) - Body ground
    		Always
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


2.CHECK HARNESS AND CONNECTOR (HEATER FUEL PUMP - BODY GROUND)


    Lexus Is250, Is220D. Gse20 Ale20.Heater.Combustion Type Power Heater System.Combustion Type Power Heater System Power Heater Fuel Pump Circuit

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

    Standard resistance:
    Tester connection
    		Condition
    		Specified condition
    Q55-1 - Body ground
    		Always
    		Below 1 Ω


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


3.INSPECT HEATER FUEL PUMP


    Lexus Is250, Is220D. Gse20 Ale20.Heater.Combustion Type Power Heater System.Combustion Type Power Heater System Power Heater Fuel Pump Circuit

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

    Standard resistance:
    Tester connection
    		Condition
    		Specified condition
    Q55-2 - Q55-1
    		Always
    		9 to 12 Ω

  1. Inspect heater fuel pump operation.

    1. Connect the positive (+) lead from the battery to terminal 2 and the negative (-) lead to terminal 1, and check the pressure of the hose by hand.

      NOTICE:
      This inspection must be done quickly (within 10 seconds) to prevent damage to the heater fuel pump.
      OK:
      The pressure is applied to the hose.


NG
REPLACE HEATER FUEL PUMP
OK


4.INSPECT POWER HEATER ECU (COMBUSTION HEATER ASSEMBLY)


    Lexus Is250, Is220D. Gse20 Ale20.Heater.Combustion Type Power Heater System.Combustion Type Power Heater System Power Heater Fuel Pump Circuit

  1. Reconnect the connector to the power heater ECU (combustion heater assembly).

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

    Standard voltage:
    Tester connection
    		Condition
    		Specified condition
    Q55-2 - Body ground
    		Engine switch: START
    Power heater switch: ON
    		10 to 14 V
    Q55-2 - Body ground
    		Engine switch: START
    Power heater switch: OFF
    		Below 1 V


NG
REPLACE POWER HEATER ECU (COMBUSTION HEATER ASSEMBLY)
OK

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE