newbie needing info

[markyboy]

hi all new member here from the uk with a small problem, i work for a subaru dealership and we have got in an svx with the dreaded 4ws light on. now we never had this setup on our spec so we have no info on it at all. we have managed to get a code for the rear wheel speed sensor but we can't seem to link any part of the 4ws to a sensor that can read the wheel speed. does anyone have any sort of workshop manual that gives wiring diagrams or an explanation of how test to system?

[Trevor]

Originally Posted by markyboy

hi all new member here from the uk with a small problem, i work for a subaru dealership and we have got in an svx with the dreaded 4ws light on. now we never had this setup on our spec so we have no info on it at all. we have managed to get a code for the rear wheel speed sensor but we can't seem to link any part of the 4ws to a sensor that can read the wheel speed. does anyone have any sort of workshop manual that gives wiring diagrams or an explanation of how test to system?

It is interesting that as a dealership you are seeking help here, rather than from Subaru.

As far as I am aware the 4ws system has no connection with a rear wheel speed sensor. But I do not have any sort of wiring diagram to confirm this.


The system is completely stand alone and derives input from a potentiometer mounted to the base of the steering column. The motor is a Mitsubishi Electric type 4WS - 88141PA000. The controller in the boot, is also Mitsubishi 4WS - 88121PA000. Connector CNI is motor power and is permanently energised. CN2 is the sensor inputs and control voltage. Motor switching is by FETs within the controller and these are stall current protected.

The above is all the information I can provide, which could be of assistance.

[markyboy]

subaru can't help as we never had this system so there is no info on it also there is the liability side that they won't help us incase something goes wrong!

what are these cn1, cn2, fet are they plugs? i found the plug for the motor with a big thick black wire and red wire and then 2 thinner wires, if the black and red are permanently live what do i do to the smaller wires to get them to move the motor?

[Trevor]

Originally Posted by markyboy

subaru can't help as we never had this system so there is no info on it also there is the liability side that they won't help us incase something goes wrong!

what are these cn1, cn2, fet are they plugs? i found the plug for the motor with a big thick black wire and red wire and then 2 thinner wires, if the black and red are permanently live what do i do to the smaller wires to get them to move the motor?

I sympathise with Subaru under the circumstances.

CN indicates a connector/plug/socket. Surely it is obvious that the smaller wires constitute a control circuit. With due respect, I would suggest that you get someone with the required experience alongside.

[b3lha]

READ THIS:

http://www.geocities.com/jamsvx/trans4ws.html

[markyboy]

i know they control it but how? thats what i'm trying to find out is it a voltage an earth or duty ratio? if i know how it works then i can test it

[Trevor]

Originally Posted by markyboy

i know they control it but how? thats what i'm trying to find out is it a voltage an earth or duty ratio? if i know how it works then i can test it

As per my previous post:-

"Motor switching is by FETs within the controller and these are stall current protected."

This would indicate that the motor is most likely controlled by a positive voltage. You can do no harm by checking at the motor connector with a high impedance meter, so as to investigate and sort out what is involved.

[b3lha]

My suggestion would be to locate the rear wheel speed sensor, located as per the diagram and then try to dismantle it and figure out how it works - or why it doesn't work. Failing that, check the wiring between it and the 4WS ECU.

Once you figure it out, please report back here so that we can benefit from your experience.

My 4WS saved my ass tonight. I was doing about 40 in the middle lane, concentrating on my mirror looking for a gap in the right lane then I suddenly realised that the car in front of me was hard on the brakes. My only option was to swerve into the left lane. The VL reacts incredibly quickly in this sort of manouvre and changes direction much faster than any normal car. I am absolutely sure I wouldn't have pulled it off in my other SVX.

[markyboy]

trouble is the only thing i can see that could read the wheel speed would be the abs sensor, i can't see any other sensor around the wheel/driveshaft thats what is so weird, and surely if that was playing up it would put the abs light on?

[Trevor]

Originally Posted by markyboy

trouble is the only thing i can see that could read the wheel speed would be the abs sensor, i can't see any other sensor around the wheel/driveshaft thats what is so weird, and surely if that was playing up it would put the abs light on?

It would appear from the sales pamphlet, that the Rear
Wheel Speed Sensor, is combined with the Rear Angle sensor, all situated behind the rear axle. In view of the units position it, it would not appear likely that individual wheel sensing is involved.

[Trevor]

Originally Posted by b3lha

My suggestion would be to locate the rear wheel speed sensor, located as per the diagram and then try to dismantle it and figure out how it works - or why it doesn't work. Failing that, check the wiring between it and the 4WS ECU.

Once you figure it out, please report back here so that we can benefit from your experience.

My 4WS saved my ass tonight. I was doing about 40 in the middle lane, concentrating on my mirror looking for a gap in the right lane then I suddenly realised that the car in front of me was hard on the brakes. My only option was to swerve into the left lane. The VL reacts incredibly quickly in this sort of manouvre and changes direction much faster than any normal car. I am absolutely sure I wouldn't have pulled it off in my other SVX.

Greetings Phil,

I have not had personal experience of SVX 4WS, but have a friend who had such a car. Incidentally he somehow wrote it off, through exiting the road and encountering a tree. It went to a local wrecker. (Parts outfit)

I understood from what my friend told me, that when reversing the rears turned opposite to the front, in order to facilitate parking within a small gap between vehicles. His wife said that she simply could not equate with this. She normally drove a Legacy.

He also said that the 4ws did not operate at higher speeds. I note from the sales blurb. --

"And the adoption of a quicker steering ratio ensures compatibility between high-speed driving and sharp handling through corners."

Could this be the main factor in the quick steering which you describe? If so I may chase up on a 4WS rack, provided it is compatible.

Cheers, Trevor.

[b3lha]

Originally Posted by Trevor

I understood from what my friend told me, that when reversing the rears turned opposite to the front, in order to facilitate parking within a small gap between vehicles. His wife said that she simply could not equate with this. She normally drove a Legacy.

He also said that the 4ws did not operate at higher speeds. I note from the sales blurb. --

Without wishing to offend your friend, I think he may have been mistaken. The system he is talking about was used on Honda Preludes. It is documented that the SVX system ONLY operates at speeds above 40km/h and the rear wheel do not turn opposite to the front ones.

Originally Posted by Trevor

"And the adoption of a quicker steering ratio ensures compatibility between high-speed driving and sharp handling through corners."

Could this be the main factor in the quick steering which you describe? If so I may chase up on a 4WS rack, provided it is compatible.

I don't think that the quicker rack is the main factor, but even at low speeds, I prefer the sharper feel of the 4WS rack. I think that you, as an ex-racing driver, would probably prefer it too.

I don't believe in replacing perfectly good parts, but if your steering rack was in need of replacement then I would suggest trying to obtain a 4WS rack.

[b3lha]

Originally Posted by markyboy

trouble is the only thing i can see that could read the wheel speed would be the abs sensor, i can't see any other sensor around the wheel/driveshaft thats what is so weird, and surely if that was playing up it would put the abs light on?

I'll have a look under mine tonight in the location indicated by the diagram and see I can figure out where the sensor might be.

[b3lha]

You're absolutely right Markyboy. I had a look under my car and I also can't see anything connected to the driveline that could measure the rear wheel speed.

I would hazard a guess that it must be getting the speed signal from the transmission speed sensors. Has this car had any transmission problems yet?

As I understand it, speed sensor 1 measures the speed of the rear wheels and speed sensor 2 measures the speed of the front wheels. The speed sensors on Jap imports are different from the UK model SVX. Speed sensor 1 is an inductive type in the back end of the transmission, just like on the UK model. But speed sensor 2 is a hall-effect type mounted in the front diff, like the USA model. There are a couple of long discussions about this if you want to want to know more.

Has anybody fitted a pulse-converter to either of the transmission speed sensors to try and delimit the car or convert it to mph?

I don't know what else I can suggest apart from following the wires from the 4WS ECU.

Phil.

[Trevor]

I am starting to think that the Subaru sales team were typical.