Toyota Corolla Cross: Rear Window Defogger System does not Operate

DESCRIPTION

An operation request signal is sent to the air conditioning amplifier assembly via LIN communication when the rear window defogger switch (air conditioning control assembly) is operated. When the air conditioning amplifier assembly receives the signal, it sends an operation request signal via CAN communication to the main body ECU (multiplex network body ECU).When the main body ECU (multiplex network body ECU) receives the signal, it sends an operation request signal via CPXI communication to the power distribution box assembly. After the operation request signal is received by the power distribution box assembly it outputs an operation signal and operates the window defogger.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

• Inspect the fuses for circuits related to this system before performing the following procedure.
• With the negative (-) auxiliary battery terminal connected, disconnect/do not connect the connector of the power distribution box assembly.
• When replacing the power distribution box assembly, the system may not operate normally if the same part number is not used.
• The window defogger system uses the CAN communication system, LIN communication system and CXPI communication system. Inspect the communication function by following How to Proceed with Troubleshooting.

  Troubleshoot the window defogger system after confirming that the communication system is functioning properly.

  Click here

• Before replacing the main body ECU (multiplex network body ECU), refer to Registration.
  • for HEV Model:

    Click here

  • for Gasoline Model:

    Click here

PROCEDURE

1.	READ VALUE USING GTS

(a) Read the Data List according to the display on the GTS.

Body Electrical > Power Distribution Box > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Rear Defogger Input Signal	Window defogger switch signal input condition	OFF or ON	OFF: Rear window defogger switch is off ON: Rear window defogger switch is on	-

Body Electrical > Power Distribution Box > Data List

Tester Display
Rear Defogger Input Signal

OK:

On the GTS screen, ON or OFF is displayed accordingly.

NG

GO TO STEP 5

OK

2.	READ VALUE USING GTS

(a) Read the Data List according to the display on the GTS.

Body Electrical > Power Distribution Box > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Rear Defogger Output Signal	Window defogger output condition	OFF or ON	OFF: Window defogger does not operate ON: Window defogger operates	-

Body Electrical > Power Distribution Box > Data List

Tester Display
Rear Defogger Output Signal

OK:

On the GTS screen, ON or OFF is displayed accordingly.

NG

REPLACE POWER DISTRIBUTION BOX ASSEMBLY

OK

3.	CHECK HARNESS AND CONNECTOR (POWER DISTRIBUTION BOX ASSEMBLY - REAR WINDOW DEFOGGER WIRE (BACK DOOR GLASS))

(a) Disconnect the 8F power distribution box assembly connector.

(b) Disconnect the U27 rear window defogger wire (back door glass) connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
8F-43 - U27-1 (B)	Always	Below 1 Ω
8F-43 or U27-1 (B) - Body ground	Always	10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.	CHECK HARNESS AND CONNECTOR (REAR WINDOW DEFOGGER WIRE (BACK DOOR GLASS) - BODY GROUND)

(a) Disconnect the U28 rear window defogger wire (back door glass) connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
U28-1 (E) - Body ground	Always	Below 1 Ω

OK

REPAIR REAR WINDOW DEFOGGER WIRE (BACK DOOR GLASS)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.	CHECK AIR CONDITIONING SYSTEM

(a) Check the air conditioning system.

• for HEV Model:

  Click here

• for Gasoline Model with Automatic Air Conditioning System:

  Click here

• for Gasoline Model with Manual Air Conditioning System:

  Click here

HINT:

Both the window defogger system operation signal and air conditioning system operation signal are transmitted to the air conditioning amplifier assembly via the same communication line.

OK:

The air conditioning system operates normally.

NG

GO TO AIR CONDITIONING SYSTEM for HEV Model: Click here for Gasoline Model with Automatic Air Conditioning System: Click here for Gasoline Model with Manual Air Conditioning System: Click here

OK

6.	CHECK AIR CONDITIONING CONTROL ASSEMBLY

(a) Check that the defogger indicator illuminates when the window defogger switch is on.

OK:

Defogger indicator illuminates.

NG

REPLACE AIR CONDITIONING CONTROL ASSEMBLY

OK

7.	PERFORM ACTIVE TEST USING GTS

(a) Using the GTS, perform the Active Test.

Body Electrical > Air Conditioner > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
Rear Defogger Relay	Rear window defogger wire (Back door glass)	OFF or ON	-

Body Electrical > Air Conditioner > Active Test

Tester Display
Rear Defogger Relay

OK:

Rear window defogger wire (back door glass) warms up.

OK

REPLACE AIR CONDITIONING CONTROL ASSEMBLY

NG

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

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