Toyota Prius: Heated Steering Wheel System

• Precaution
• Parts Location
• System Diagram
• Problem Symptoms Table
• Terminals Of Ecu
• Fail-safe Chart
• Data List / Active Test
• Inspection
• Steering Wheel does not Heat Up When Heated Steering Wheel Switch is Pressed

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.

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HINT:

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

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HANDLING PRECAUTIONS FOR SRS AIRBAG SYSTEM

CAUTION:

This Toyota Prius vehicle is equipped with a Supplemental Restraint System (SRS). Failure to carry out service operations in the correct sequence could cause the SRS to unexpectedly deploy during servicing. This may cause a serious accident.

Before servicing (including inspection, replacement, removal and installation of parts), be sure to read the precautionary notices for Supplemental Restraint System.

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Parts Location

PARTS LOCATION

ILLUSTRATION

*1	NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY - STRG HTR FUSE - ECU-IGP NO.3 FUSE	*2	STEERING WHEEL ASSEMBLY - STEERING WHEEL HEATER UNIT
*3	STEERING HEATER SWITCH	*4	HEATED STEERING WHEEL CONTROLLER (MULTIPLEX NETWORK STEERING ECU)
*5	DLC3	*6	SPIRAL CABLE SUB-ASSEMBLY
*7	COMBINATION METER ASSEMBLY	*8	AIR CONDITIONING CONTROL ASSEMBLY
*9	AIR CONDITIONING AMPLIFIER ASSEMBLY	*10	POWER DISTRIBUTION BOX ASSEMBLY - ECU-B NO.3 FUSE

System Diagram

SYSTEM DIAGRAM

SYSTEM DIAGRAM

Problem Symptoms Table

PROBLEM SYMPTOMS TABLE

Heated Steering Wheel System

Symptom	Suspected Area	Link
Steering wheel does not heat up when heated steering wheel switch is pressed	STRG HTR fuse	-
	ECU-IGP NO. 3 Fuse	-
	ECU-B NO. 3 Fuse	-
	Harness or connector	-
	CAN communication system
	Air conditioning system
	Meter / Gauge system
	Spiral cable sub-assembly
	Steering heater switch
	Refer to "Steering wheel does not heat up when heated steering wheel switch is pressed"

Terminals Of Ecu

TERMINALS OF ECU

HEATED STEERING WHEEL CONTROLLER (MULTIPLEX NETWORK STEERING ECU)

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

HINT:

Perform the inspection from the harness side with the connectors connected.

Terminal No. (Symbol)	Terminal Description	Condition	Specified Condition
A-1 (GND) - Body ground	Ground	Always	Below 1 Ω
A-2 (CXPI) - Body ground	CXPI communication signal	Power switch ON (IG)	Pulse generation
A-4 ( B) - Body ground	ECU power supply	Power switch OFF	11 to 14 V
B-5 (HETATER ) - Body ground	Heater output signal	Power switch ON (IG), Heated steering wheel system operating	11 to 14 V*1
B-4 (NTC ) - Body ground	Thermistor input signal	Power switch ON (IG), Heated steering wheel system operating	2.5 to 4.8 V*2
B-3 (NTC ) - Body ground	Thermistor ground	Power switch ON (IG), Heated steering wheel system operating	Below 1 V

Fail-safe Chart

FAIL-SAFE CHART

FAIL-SAFE FUNCTION

(a) Operation when a malfunction is detected

Content	Operation
A thermistor malfunction (open) is detected	Heater output off
A thermistor malfunction (short) is detected	Heater output off
A heater malfunction is detected	Heater output off
An abnormally high voltage malfunction is detected	Heater output off
An abnormally low voltage malfunction is detected	Heater output off
A communication malfunction is detected	Heater output off
A malfunction is detected during the initial check	Heater output off

Data List / Active Test

DATA LIST / ACTIVE TEST

DATA LIST

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
Steering Heater	Steering wheel heater operation status	ON/OFF	ON: Operating OFF: Not 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
Steering Heater	Operate the steering wheel heater	ON/OFF	Confirm that the Toyota Prius vehicle is stopped with the ignition switch ON.

Inspection

INSPECTION

PROCEDURE

1. INSPECT STEERING HEATER SWITCH

*a	Component without harness connected

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

Standard Resistance:

Tester Connection	Condition	Specified Condition	Result
5(IG) - 2(E)	Steering heater switch is pushed	Below 1 Ω	Ω
5(IG) - 2(E)	Steering heater switch is not pushed	10 kΩ or higher	kΩ

(b) Indicator Inspection

(1) Apply auxiliary battery voltage to the steering heater switch and check that the indicator illuminates.

OK:

Condition	Specified Condition
Auxiliary battery positive ( ) → Terminal 3 (D)Auxiliary battery negative (-) → Terminal 4 (B)	Illuminates

Steering Wheel does not Heat Up When Heated Steering Wheel Switch is Pressed

DESCRIPTION

The heated steering wheel system heats the steering wheel assembly when the system is turned on using the steering heater switch.

The heated steering wheel system uses a thermistor inside of the steering wheel assembly to detect the heater temperature and maintain the set temperature.

A thermostat is installed in the steering wheel heater unit as a safety mechanism.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

The Toyota Prius vehicle is equipped with a Supplemental Restraint System (SRS) which includes components such as airbags. Before servicing (including removal or installation of parts), be sure to read the precaution for Supplemental Restraint System.

Click here

PROCEDURE

1.	INSPECT STEERING WHEEL ASSEMBLY (THERMOSTAT, HEATER AND THERMISTOR)

(a) Disconnect the B heated steering wheel controller (multiplex network steering ECU) connector.

*a Component without harness connected (Steering Wheel Assembly)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
B-5(HEATER ) - B-1(GND)	23°C (73°F)	2.25 to 2.75 Ω
B-4(NTC ) - B-3(NTC-)	25°C (77°F)	9.5 to 10.5 kΩ

OK

REPLACE HEATED STEERING WHEEL CONTROLLER (MULTIPLEX NETWORK STEERING ECU)

NG

REPLACE STEERING WHEEL ASSEMBLY