Toyota Prius: Power Steering Ecu

Toyota Prius (XW60) 2023-2025 Service Manual / Steering / Power Assist Systems / Power Steering Ecu

Removal
Installation
Power Steering Ecu Initial Setting
End Position Initial Setting

Removal

REMOVAL

CAUTION / NOTICE / HINT

The necessary procedures (adjustment, calibration, initialization, or registration) that must be performed after parts are removed and installed, or replaced during the power steering ECU assembly removal/installation are shown below.

Necessary Procedures After Parts Removed/Installed/Replaced

Replaced Part or Performed Procedure	Necessary Procedure	Effect/Inoperative Function when Necessary Procedure not Performed
Power steering ECU assembly	Update ECU security key	Toyota Prius Vehicle control history (RoB) are stored
	ECU configuration	Vehicle Control History (RoB) are stored EPS warning light illuminates
	Perform power steering ECU initial setting (torque sensor zero point calibration and assist map writing)	Toyota Prius Vehicle Control History (RoB) are stored EPS warning light illuminates
	End position initial setting	-

CAUTION / NOTICE / HINT

HINT:

When the cable is disconnected / reconnected to the auxiliary battery terminal, systems temporarily stop operating. However, each system has a function that completes learning the first time the system is used.

Learning completes when Toyota Prius vehicle is driven

Effect/Inoperative Function when Necessary Procedure not Performed	Necessary Procedure	Link
Front Camera System	Drive the Toyota Prius vehicle straight ahead at 35 km/h (22 mph) or more for 5 seconds or more.

Learning completes when vehicle is operated normally

Effect/Inoperative Function when Necessary Procedure not Performed	Necessary Procedure	Link
1: w/o Power Back Door System 2: w/ Power Back Door System
Power Door Lock Control System*1 Back door opener	Perform door unlock operation with door control switch or electrical key transmitter sub-assembly switch.
Power Back Door System*2	Reset back door close position
Air Conditioning System	for HEV Model: After the ignition switch is turned to ON, the servo motor standard position is recognized. for PHEV Model: After the ignition switch is turned to ON, the servo motor and cooler expansion valve standard position is recognized.	-

CAUTION / NOTICE / HINT

COMPONENTS (REMOVAL)

Procedure		Part Name Code
1	STEERING COLUMN ASSEMBLY	-	-	-	-
2	POWER STEERING ECU ASSEMBLY	89650		-	-
3	ELECTRIC POWER STEERING MOTOR SHAFT DAMPER	45254B	-	-	-

*1	ELECTRIC POWER STEERING COLUMN SUB-ASSEMBLY	-	-
●	Non-reusable part	-	-

PROCEDURE

1. REMOVE STEERING COLUMN ASSEMBLY

Click here

2. REMOVE POWER STEERING ECU ASSEMBLY

NOTICE:

Do not drop the power steering ECU assembly, strike it with tools or subject it to impacts.
If the power steering ECU assembly is subjected to an impact, replace it with a new one.
Do not pull the wire harness of the electric power steering column sub-assembly.
Do not allow any moisture to come into contact with the power steering ECU assembly.
Do not loosen any bolts not mentioned in the procedure.
Do not allow any foreign matter to contaminate the power steering ECU assembly.

3. REMOVE ELECTRIC POWER STEERING MOTOR SHAFT DAMPER

Installation

INSTALLATION

CAUTION / NOTICE / HINT

COMPONENTS (INSTALLATION)

Procedure		Part Name Code
1	ELECTRIC POWER STEERING MOTOR SHAFT DAMPER	45254B		-	-
2	POWER STEERING ECU ASSEMBLY	89650		-	-
3	STEERING COLUMN ASSEMBLY	-	-	-	-

*1	ELECTRIC POWER STEERING COLUMN SUB-ASSEMBLY	-	-
	Tightening torque for "Major areas involving basic Toyota Prius vehicle performance such as moving/turning/stopping": Nm (kgfcm, ft.*lbf)	●	Non-reusable part
	Grease	-	-

PROCEDURE

1. INSTALL ELECTRIC POWER STEERING MOTOR SHAFT DAMPER

Grease

(1) Apply grease to a new electric power steering motor shaft damper.

NOTICE:

First wipe off the existing grease from the serrated part, and then apply the dedicated grease supplied with a new power steering ECU assembly or electric power steering column sub-assembly.

(2) Install the electric power steering motor shaft damper.

2. INSTALL POWER STEERING ECU ASSEMBLY

NOTICE:

Do not drop the power steering ECU assembly, strike it with tools or subject it to impacts.
If the power steering ECU assembly is subjected to an impact, replace it with a new one.
Do not pull the wire harness of the electric power steering column sub-assembly.
Do not allow any moisture to come into contact with the power steering ECU assembly.
Do not loosen any bolts not mentioned in the procedure.
Do not allow any foreign matter to contaminate the power steering ECU assembly.

*a	Wooden Block	*b	Cloth
	Rotate		Turn

(1) Temporarily install the power steering ECU assembly with the 2 bolts.

NOTICE:

When temporarily installing the 2 bolts to the power steering ECU assembly, do not tighten them all the way down.

(2) Using a 10 mm hexagon socket wrench, install the steering wheel assembly set bolt to the steering main shaft.

NOTICE:

Do not apply excessive torque to the steering wheel assembly set bolt by using a tool such as an impact wrench.

HINT:

The steering wheel assembly set bolt is used for turning the steering main shaft during inspection of the steering main shaft rotating torque. Remove the steering wheel assembly set bolt after performing this inspection.

(3) Secure the steering column assembly in a vise using aluminum plates, cloths and wooden blocks.

NOTICE:

Do not overtighten the vise, as the steering column assembly may become deformed.
Support the steering column assembly with wooden blocks or similar items to ensure that it does not fall.
Secure the power steering ECU assembly so that it faces straight up.

(4) Rotate the steering main shaft 180 degrees counterclockwise and then 180 degrees clockwise at a speed of 60 rpm, and repeat 2 to 3 times to center the axis of the power steering ECU assembly. [*1]

(5) Tighten the 2 bolts. [*2]

Torque:

18.5 N·m {189 kgf·cm, 14 ft·lbf}

(6) Using a torque wrench, measure the turning torque of the steering main shaft.

Preload:

1.0 to 2.3 N*m (11 to 23 kgf*cm, 9 to 20 in.*lbf)

NOTICE:

Ensure that there is no abnormal resistance during rotation.

(7) If the turning torque is not as specified, loosen the 2 bolts and repeat steps [*1] and [*2] to recenter the axis of the power steering ECU assembly.

(8) Connect the connector.

3. INSTALL STEERING COLUMN ASSEMBLY

Click here

Power Steering Ecu Initial Setting

POWER STEERING ECU INITIAL SETTING

PROCEDURE

1. POWER STEERING ECU INITIAL SETTING (TORQUE SENSOR ZERO POINT CALIBRATION AND ASSIST MAP WRITING)

NOTICE:

If any of the following conditions are met, perform Power Steering ECU Initial Setting (torque sensor zero point calibration and assist map writing):

The power steering ECU assembly has been replaced.
The electric power steering column sub-assembly has been replaced.
There is a difference in steering effort between turning left and right.

(a) Perform Power Steering ECU Initial Setting (torque sensor zero point calibration and assist map writing).

(1) Align the front wheels straight ahead and center the steering wheel.

(2) Turn the ignition switch off.

(3) Connect the GTS to the DLC3.

(4) Turn the ignition switch to ON.

(5) Turn the GTS on.

(6) Enter the following menus: Chassis / EMPS / Utility / Power Steering ECU Initial Setting.

Chassis > EMPS > Utility

Tester Display
Power Steering ECU Initial Setting

NOTICE:

Do not turn the steering wheel sharply.
During the torque sensor zero point calibration the steering wheel will shudder. Do not touch the steering wheel until at least 3 seconds have elapsed after the shuddering has stopped.

(7) Check for RoBs.

Click here

Chassis > EMPS > Utility

Tester Display
Toyota Prius Vehicle Control History (RoB)

NOTICE:

When Power Steering ECU Initial Setting (torque sensor zero point calibration and assist map writing) are completed, make sure to check for vehicle control history (RoB).

End Position Initial Setting

END POSITION INITIAL SETTING

CAUTION / NOTICE / HINT

Perform end position initial setting after replacing or servicing parts related to steering operation.

NOTICE:

If matchmarks were not placed when removing parts related to steering operation, perform end position initial setting.

Removed or Replaced Part	Work	End Position Initial Setting
○: Necessary -: Unnecessary
Power steering ECU with motor assembly	Removing	-
Power steering ECU with motor assembly	Replacing	○
Electric power steering column sub-assembly	Removing	-
Electric power steering column sub-assembly	Replacing	○
No. 2 steering intermediate shaft assembly	Removing	-
No. 2 steering intermediate shaft assembly	Replacing	○
Steering gear assembly	Removing	-
Steering gear assembly	Replacing	○

NOTICE:

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

PROCEDURE

1. END POSITION INITIAL SETTING

(a) Align the front wheels straight ahead and center the steering wheel.

(b) Perform end position learning value clear. (*1)

When using GTS:

Perform end position learning value clear according to the instructions on the GTS screen.

Chassis > EMPS > Utility

Tester Display
End Position Learning Value Clear

When not using GTS:

Turn the ignition switch off.
Disconnect the cable from the negative (-) auxiliary battery terminal and wait for at least 40 seconds.
for M20A-FXS: Click here

for 2ZR-FXE: Click here
Connect the cable to the negative (-) auxiliary battery terminal.
for M20A-FXS: Click here

for 2ZR-FXE: Click here