Toyota Prius: Windshield Deicer System

Toyota Prius (XW60) 2023-2025 Service Manual / Vehicle Exterior / Window / Glass / Windshield Deicer System

Precaution
Parts Location
System Diagram
How To Proceed With Troubleshooting
Operation Check
Problem Symptoms Table
Terminals Of Ecu
Data List / Active Test
Windshield Deicer does not Operate

Precaution

PRECAUTION

PRECAUTIONS FOR DISCONNECTING CABLE FROM NEGATIVE (-) AUXILIARY BATTERY TERMINAL

NOTICE:

After the ignition switch is turned off, there may be a waiting time before disconnecting the negative (-) auxiliary battery terminal.

Click here

HINT:

When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

Click here

Parts Location

PARTS LOCATION

ILLUSTRATION

*1	WINDSHIELD GLASS - WINDSHIELD DEICER WIRE	*2	AIR CONDITIONING AMPLIFIER ASSEMBLY
*3	AIR CONDITIONING CONTROL ASSEMBLY	*4	FRONT WINDOW DEICER SWITCH
*5	NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY - DEICER RELAY - DEICER FUSE - ECU-IGP NO. 3 FUSE	*6	POWER DISTRIBUTION BOX ASSEMBLY - ECU-IGR NO. 1 FUSE
*7	DLC3	-	-

System Diagram

SYSTEM DIAGRAM

How To Proceed With Troubleshooting

CAUTION / NOTICE / HINT

HINT:

Use the following procedure to troubleshoot the windshield deicer system.
*: Use the GTS.

PROCEDURE

1.	Toyota Prius Vehicle BROUGHT TO WORKSHOP

2.	CUSTOMER PROBLEM ANALYSIS

HINT:

In troubleshooting, confirm that the problem symptoms have been accurately identified. Preconceptions should be discarded in order to make an accurate judgment. To clearly understand what the problem symptoms are, it is extremely important to ask the customer about the problem and the conditions at the time the malfunction occurred.
Gather as much information as possible for reference. Past problems that seem unrelated may also help in some cases.

The following 5 items are important points for problem analysis:

What	Toyota Prius Vehicle model, system name
When	Date, time, occurrence frequency
Where	Road conditions
Under what conditions?	Driving conditions, weather conditions
How did it happen?	Problem symptoms

PRE-CHECK

(a) Measure the auxiliary battery voltage with the ignition switch off.

Standard Voltage:

11 to 14 V

If the voltage is below 11 V, recharge or replace the auxiliary battery before proceeding to the next step.

(b) Check the fuses and relays.

(c) Check the connector connections and terminals to make sure that there are no abnormalities such as loose connections, deformation, etc.

4.	INSPECT COMMUNICATION FUNCTION OF CAN COMMUNICATION SYSTEM*

(a) Using the GTS, check for CAN communication system DTCs.

for HEV Model: Click here

for PHEV Model: Click here

Result	Proceed to
CAN DTCs are not output	A
CAN DTCs are output	B

GO TO CAN COMMUNICATION SYSTEM

for HEV Model: Click here

for PHEV Model: Click here

5.	PROBLEM SYMPTOMS TABLE

(a) Refer to Problem Symptoms Table.

Click here

Result	Proceed to
Fault is not listed in Problem Symptoms Table.	A
Fault is listed in Problem Symptoms Table.	B

GO TO STEP 7

6.	OVERALL ANALYSIS AND TROUBLESHOOTING*

(a) Operation Check

Click here

(b) Terminals of ECU

Click here

(d) On-Toyota Prius vehicle Inspection

7.	REPAIR OR REPLACE

8.	CONFIRMATION TEST

END

Operation Check

OPERATION CHECK

CHECK WINDSHIELD DEICER SYSTEM

NOTICE:

If the windshield deicer system is operated when the auxiliary battery voltage is low, due to the electrical load limit control that gives voltage supply priority to the power steering system, the windshield deicer system may not operate. In this case, check the Toyota Prius vehicle control history (RoB) of the power steering system and check that "Battery Voltage Drop: X208F" is not stored before proceeding with troubleshooting.

Click here

(a) Turn the ignition switch to ON.

(b) Check that the windshield deicer wire (windshield glass) becomes warm by operating the front window deicer switch of the air conditioning control assembly.

Problem Symptoms Table

PROBLEM SYMPTOMS TABLE

NOTICE:

Click here

HINT:

Use the table below to help determine the cause of problem symptoms. If multiple suspected areas are listed, the potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected areas in the order they are listed. Replace parts as necessary.
Inspect the fuses and relays related to this system before inspecting the suspected areas below.

Windshield Deicer System

Symptom	Suspected Area	Link
Windshield deicer does not operate	Proceed to the "Windshield Deicer does not Operate"

Terminals Of Ecu

TERMINALS OF ECU

for Type A:

for Type B:

CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY

(a) Disconnect the K74 air conditioning amplifier assembly connector.

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

HINT:

Measure the values on the wire harness side with the connector disconnected.

Terminal No. (Symbol)	Terminal Description	Condition	Specified Condition
K74-5 (B) - K74-17 (GND)	Auxiliary battery power supply	Ignition switch off	11 to 14 V
K74-6 (IG ) - K74-17 (GND)	Power source (IG)	Ignition switch ON	11 to 14 V
K74-6 (IG ) - K74-17 (GND)	Power source (IG)	Ignition switch off	Below 1 V
K74-17 (GND) - Body ground	Ground	Always	Below 1 Ω

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

Terminal No. (Symbol)	Terminal Description	Condition	Specified Condition
K74-22 (FDEF) - K74-17 (GND)	Windshield deicer signal	Ignition switch ON, front window deicer switch off	11 to 14 V
K74-22 (FDEF) - K74-17 (GND)	Windshield deicer signal	Ignition switch ON, front window deicer switch on	Below 2.2 V

(e) Check for pulses according to the value(s) in the table below.

Terminal No. (Symbol)	Terminal Description	Condition	Specified Condition
K74-7 (LIN1) - K74-17 (GND)	LIN communication line	Ignition switch ON	Pulse generation

CHECK AIR CONDITIONING CONTROL ASSEMBLY

(a) Disconnect the K68 air conditioning control assembly connector.

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

Terminal No. (Symbol)	Terminal Description	Condition	Specified Condition
K68-1 (IG ) - K68-16 (GND)	Power source (IG)	Ignition switch ON	11 to 14 V
K68-1 (IG ) - K68-16 (GND)	Power source (IG)	Ignition switch off	Below 1 V
K68-16 (GND) - Body ground	Ground	Always	Below 1 Ω

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

Terminal No. (Symbol)	Terminal Description	Condition	Specified Condition
K68-10 (SW3) - K68-16 (GND)	Front window deicer switch signal	Ignition switch ON, front window deicer switch off	11 to 14 V
K68-10 (SW3) - K68-16 (GND)	Front window deicer switch signal	Ignition switch ON, front window deicer switch on	Below 1 V
K68-4 (SWC) - K68-16 (GND)	Front window deicer switch indicator signal	Ignition switch ON, front window deicer switch off	Below 1 V
K68-4 (SWC) - K68-16 (GND)	Front window deicer switch indicator signal	Ignition switch ON, front window deicer switch on	11 to 14 V

(e) Check for pulses according to the value(s) in the table below.

Terminal No. (Symbol)	Terminal Description	Condition	Specified Condition
K68-14 (LIN1) - K68-16 (GND)	LIN communication line	Ignition switch ON	Pulse generation

Data List / Active Test

DATA LIST / ACTIVE TEST

DATA LIST

NOTICE:

In the following table, the values listed under "Normal Condition" are reference values. Do not depend solely on these reference values when deciding whether a part is faulty or not.

HINT:

Using the GTS to read the Data List allows the values or states of switches, sensors, actuators and other items to be read without removing any parts. This non-intrusive inspection can be very useful because intermittent conditions or signals may be discovered before parts or wiring is disturbed. Reading the Data List information early in troubleshooting is one way to save diagnostic time.

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

Body Electrical > Air Conditioner > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Front Deicer Relay	Status of the front deicer relay	OFF or ON	OFF: Windshield deicer not operating ON: Windshield deicer operating	-

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Front Deicer Relay

Status of the front deicer relay

OFF or ON

OFF: Windshield deicer not operating

ON: Windshield deicer operating

ACTIVE TEST

HINT:

Using the GTS to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.

(a) Perform the Active Test according to the display on the GTS.

Body Electrical > Air Conditioner > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
Front Deicer Relay	Windshield deicer wire	OFF or ON	-

Windshield Deicer does not Operate

DESCRIPTION

When the front window deicer switch is operated, a switch operation signal is output to the air conditioning control assembly.The air conditioning control assembly sends an operation request signal to the air conditioning amplifier assembly via LIN communication.When the operation request signal is received, the air conditioning amplifier assembly turns the deicer relay on to operate the windshield deicer system.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.
If the windshield deicer system is operated when the auxiliary battery voltage is low, due to the electrical load limit control that gives voltage supply priority to the power steering system, the windshield deicer system may not operate. In this case, check the Toyota Prius vehicle control history (RoB) of the power steering system and check that "Battery Voltage Drop: X208F" is not stored before proceeding with troubleshooting.
Click here

PROCEDURE

1.	CHECK AIR CONDITIONING SYSTEM

(a) Check that the air conditioning system.

HINT:

Both the windshield deicer system operation signal and airconditioning system operation signal are transmitted to the airconditioning amplifier assembly through same communication line.

OK:

The air conditioning system operates normally.

GO TO AIR CONDITIONING SYSTEM

for HEV Model: Click here

for PHEV Model: Click here

2.	PERFORM ACTIVE TEST USING GTS

(a) Perform the Active Test according to the display on the GTS.

Body Electrical > Air Conditioner > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
Front Deicer Relay	Windshield deicer wire (windshield glass)	OFF or ON	-

Body Electrical > Air Conditioner > Active Test

Tester Display
Front Deicer Relay

OK:

The windshield deicer system operates normally.

GO TO STEP 6

3.	INSPECT FRONT WINDOW DEICER SWITCH

Click here

REPLACE FRONT WINDOW DEICER SWITCH

4.	CHECK WIRE HARNESS AND CONNECTOR (FRONT WINDOW DEICER SWITCH - POWER SOURCE)

(a) Disconnect the K31 front window deicer switch connector.

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

Standard Voltage:

Click Location & Routing(K31) Click Connector(K31)

Tester Connection	Condition	Specified Condition
K31-3 (D) - Body ground	Ignition switch off	Below 1 V
K31-3 (D) - Body ground	Ignition switch ON	11 to 14 V

Standard Resistance:

Click Location & Routing(K31) Click Connector(K31)

Tester Connection	Condition	Specified Condition
K31-2 (E) - Body ground	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.	CHECK WIRE HARNESS AND CONNECTOR (FRONT WINDOW DEICER SWITCH - AIR CONDITIONING CONTROL ASSEMBLY)

(a) Disconnect the K68 air conditioning control assembly connector.

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

Standard Resistance:

Click Location & Routing(K31,K68) Click Connector(K31) Click Connector(K68)

Tester Connection	Condition	Specified Condition
K31-4 (IND) - K68-4 (SWC)	Always	Below 1 Ω
K31-4 (IND) or K68-4 (SWC) - Body ground	Always	10 kΩ or higher
K31-5 (IG) - K68-10 (SW3)	Always	Below 1 Ω
K31-5 (IG) or K68-10 (SW3) - Body ground	Always	10 kΩ or higher

REPLACE AIR CONDITIONING CONTROL ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR

6.	INSPECT DEICER RELAY

Click here

REPLACE DEICER RELAY

7.	CHECK WIRE HARNESS AND CONNECTOR (DEICER RELAY - IG POWER SUPPLY)

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
DEICER relay holder terminal 1 - Body ground	Ignition switch ON	11 to 14 V
DEICER relay holder terminal 3 - Body ground	Ignition switch off	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

8.	CHECK WIRE HARNESS AND CONNECTOR (DEICER RELAY - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect K74 air conditioning amplifier assembly connector.

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

Standard Resistance:

Click Location & Routing(K74) Click Connector(K74)

Tester Connection	Condition	Specified Condition
DEICER relay holder terminal 2 - K74-22 (FDEF)	Always	Below 1 Ω
DEICER relay holder terminal 2 or K74-22 (FDEF) - Body ground	Always	10 kΩ higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

9.	CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY

(a) Reconnect the K74 air conditioning amplifier assembly connector.

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

Standard Voltage:

Click Location & Routing(K74) Click Connector(K74)

Tester Connection	Condition	Specified Condition
K74-22 (FDEF) - K74-17 (GND)	Ignition switch ON, front window deicer switch on	Below 2.2 V
K74-22 (FDEF) - K74-17 (GND)	Ignition switch ON, front window deicer switch off	11 to 14 V