Power Steering,[electric]

[Geoff Peace]

Toyota Yaris 1 litre 2005 model electric power steering. Had a little problem with this the other day, the warning light came on while I was warming it up on the drive. The handbook says if the engine is raced for more than 30 seconds the power steering will decrease to prevent overheating, restart the engine and drive. I did this, light went out and it has been O.K. since. This problem has never occurred before and the engine has been raced to ensure the engine is hot for the MOT without any problems. Does anyone know how this system operates? There are no hydraulics, the motor is somewhere under the dash and must engage with the steering column directly, or through some form of clutch. How is it controlled? by an ECU or some mechanical means. Does it reverse to turn left and right? Does the motor run continuously or only when required for turning? I would very much like to know for future maintenance. If anyone has any information I would be most grateful. [The Haynes manual only deals with the hydraulic form of power seering]

Regards Geoff Peace.

[dawesy]

controlled by an ECU. not 100% on the inner workings but IIRC it is direct drive to the column.

a small overview is here.

it is the denso system that is fitted to the yaris as well

[BALIKBAYAN]

Here is the text copied from page 10 in the Toyota workshop manaul for power steering for the 2007 Yaris.

SYSTEM DESCRIPTION

1. DESCRIPTION

The EPS (Electronic Power Steering) system generates

torque through the operation of the motor and the

reduction gear installed on the column shaft in order to

assist power steering effort.

The power steering ECU determines the direction and

the amount of assisting power in accordance with the

vehicle speed signals and signals from the torque sensor

built into the steering column assembly. As a result,

steering effort is controlled to be light during low speed

driving and moderately high during high speed driving.

(a) Power steering ECU:

The power steering ECU calculates assisting power

based on steering torque signals from the torque

sensor and vehicle speed signals from the skid

control ECU.

For vehicles without ABS, the power steering ECU

receives vehicle speed signals from the

speedometer.

(B) Torque sensor:

The torque sensor detects the steering effort

generated when the steering wheel is turned and

converts it to an electrical signal.

© EPS motor:

The EPS motor is activated by the current from the

power steering ECU and generates torque to assist

the steering effort.

[Jamesbelfast]

Electric power steering is fitted to many makes of modern cars. One thing that will affect their operation is poor voltage and especially after a cold start-up, this is temporary fault is not uncommon. I suspect that was happening when you where letting the car idle and the alternator had a heavy load but insufficicent rpm to cope with the demand. Duff batteries are also known to cause such issues. When this type of power steering causes problems the first thing to check is the condition of the Battery and the voltage output of the alternator.:)

[BALIKBAYAN]

Geoff, I'll try to e-mail you the power steering chapter from 2007 Yaris workshop manual.

[Geoff Peace]

Thankyou very much Balikbayan for your kind offer. However I have been directed to an American site by a friend who is far better than me on a computer, I am very much a beginner with this internet stuff! On the site he downloaded the power steering section fron the manual for a 2007 Yaris. Which as you say has the same steering system as mine. I ploughed through the whole 93 pages of it and know know how it operates. The steering on my car has been perfect ever since and since the handbook mentioned that the illumination of the P/S light may not necessarily indicate a fault it would seem to be a feature of the system, Just rather worrying when it happens if you do not know about it. Heartbeat back to normal now and thankyou once again and everyone else who replied. A Happy New Year to you all.

Regards Geoff Peace.

[BALIKBAYAN]

You're welcome.