COMBUSTION TYPE POWER HEATER SYSTEM - Power Heater Switch Circuit

DESCRIPTION

When the power heater switch is turned on, the power heater ECU (combustion heater assembly) sends a drive signal to the heater fuel pump. The combustion heater assembly then receives fuel necessary for combustion and starts operating.

WIRING DIAGRAM

Combustion Type Power Heater System - Power Heater Switch Circuit. HEATER. Lexus IS250 IS220d GSE20 ALE20

INSPECTION PROCEDURE

1.INSPECT POWER HEATER SWITCH

Combustion Type Power Heater System - Power Heater Switch Circuit. HEATER. Lexus IS250 IS220d GSE20 ALE20

Measure the resistance.

Remove the power heater switch.

Disconnect the connector from the power heater switch.

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

Standard resistance:
Tester connection
(Symbols) Condition Specified condition
J95-3 (IG) - J95-4 (IN) Power heater switch: ON Below 1 Ω
J95-3 (IG) - J95-4 (IN) Power heater switch: OFF 10 kΩ or higher

Check that the power heater switch operation indicator comes on.

Connect the positive (+) lead from the battery to terminal 4 (IN) and the negative (-) lead to terminal 6 (E), and check that the operation indicator comes on.

OK:
Indicator comes on.

Check that the power heater switch illumination comes on.

Connect the positive (+) lead from the battery to terminal 1 (ILL+) and the negative (-) lead to terminal 2 (ILL-), and check that the switch illumination comes on.

OK:
Illumination comes on.

NG

REPLACE POWER HEATER SWITCH

OK

2.CHECK HARNESS AND CONNECTOR (POWER HEATER ECU (COMBUSTION HEATER ASSEMBLY) - BATTERY)

Remove the power heater ECU (combustion heater assembly).

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

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

Standard voltage:

Tester connection (Symbols)	Condition	Specified condition
A51-3 (IG) - Body ground	Engine switch: on (IG) Power heater switch: ON	10 to 14 V
A51-3 (IG) - Body ground	Engine switch: on (IG) Power heater switch: OFF	Below 1 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.CHECK HARNESS AND CONNECTOR (POWER HEATER SWITCH - BODY GROUND)

Disconnect the connector from the power heater switch.

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

Standard resistance:
Tester connection
(Symbols) Condition Specified condition
J95-6 (E) - Body ground Always Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

LEXUS IS250, IS220d / GSE20 ALE20

HEATER

Lexus IS250 IS220d GSE20 ALE20

COMBUSTION TYPE POWER HEATER SYSTEM