Speed Sensor in a '90 Legacy? HELP!

[mikeamondo]

We're trying to have a mechanic install a computer device in our 90 Legacy Wagon, designed to record several items while the car is being driven, including acceleration, cornering, braking and speed. This, of course, is to help our teenagers drive like normal people instead of teenagers. (Sorry to any younger folk on here, but I'd rather they feel untrusted and alive than trusted and dead!)

Anyway, the manufacturer of the computer says we need to hook into the vehicle speed sensor, but that the 90 Legacy's age might mean that it only gets speed info from a traditional speedometer cable. I know it has a cable, but does it also acquire a speed "pulse" through an electronic speed sensor of some type? It seems like it might collect it for purposes other than the speedometer. The unit is all hooked up and ready to go, except for the speed line.

 

I've been told a transducer, installed inline with the speedometer cable, will generate the need 'pulse', but I was hoping to find a direct connection in the system first.

 

Thanks,

Mike

[Cougar]

Josh (Legacy777) or Skip should be able to tell you right off what needs to be done ( JOSH! SKIP! Where are those guys?). I think you may need to add the sensor for that model to do what you want to do but they can tell you for sure.

[Legacy777]

The speedometer is transferred from mechanical to electrical in the combination unit (dash gauge). It's signal is sent to the ECU.

 

You should be able to find the speed sensor input to the ECU, and tap into it there

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/ECU_I-O_page1.jpg

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/ECU_I-O_page2.jpg

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/ECU_I-O_page3.jpg

[mikeamondo]

Wow! Thanks for the lightening quick response! If I understand the diagrams you sent... Connector B58, number 11 should be carrying the electronic pulse from the speed sensor.... and all we should need to do is tie into that wire at the connector.... is that right? (sorry to be so clueless here!)

 

 

thanks!

Mike

[Cougar]

Yes, that is correct if your device can use a zero to five volt input signal. This is a logic signal level and I'm pretty sure that will work for your device. I assume your device has a high input impedence so it won't load down the source.

[Legacy777]

You're welcome.

 

Let us know how it turns out.

[mikeamondo]

Okay guys...... I've had to take this project on myself, as the connection from the mechanic didn't turn out quite right. So.... the newbie asks...... Where the heck is the ECU? Under the dash, beside the steering column... where you can only see by contorting yourself half in and half out of the car, with your head on the brake pedal.... there is a brass colored box, about the size of wireless router box, (it's what I'm looking at), mounted on a 45 degree angle, with a row of connectors in the end. My mechanic thought that this was the ecu, and the the diagrams listed above, were those connectors in the end. However, the connectors don't match the diagram. Not the right number of pins. Is this, in fact, the ecu, and if so, why doesn't it match the diagram?

 

I also downloaded the 1992 engine and electrical guide from the same folder as the diagrams, and began a search for the B58 connector. I was thinking that this fabled connector was, in fact, the source of the diagram, and where the speed wire should be hooked. More contortion. More pain. No connector. It's supposed to be yellow. Would appreciate knowing if that is in fact what I need to find, and, if so, where the heck is it?

 

As a reminder, I need to find a source for the speed "pulse". Would also be helpful if I knew how many pulses per sec. it produced.... Fords make 8000.... how about Subs?

 

This should get me started......

 

Thanks!

Mike

[ShawnW]

It is the size of a wireless router and has 4 bright yellow plugs going into it. 2 small 10MM nuts secure it and it is up under there where your mechanic is refering to. Dont however confuse it with the TCU (trans computer) which has black connectors.

 

Im sorry but I dont think what you are doing is worth it. Go find an old non turbo automatic Subaru GL from 80-84 if you want that kind of performance.

[mikeamondo]

Thanks for the reply, ShawnW..... I'll see if I can find the box with the yellow plugs. We've taken the project away from the mechanic.... I found the other box I described whilst under the dash myself..... It has black plugs, and I suspect it might be the TCU as you mention. It is into this unit that he connected the speed pulse wire. Where would the ECU be in relation to the TCU? Is the TCU the first box you would see looking up, under the dash beneath the steering wheel? Any help here is greatly appreciated!

 

As to the performance comment.... I have no idea what you mean. We're trying to install a computer to monitor how our teenagers are driving the car. If I could make it go slower, I would! Again... sorry to those of you reading this who would say the computer is violating thier trust..... but I don't really care.... I just want them to staty alive while they learn how to drive.

 

Thanks!

Mike

[mikeamondo]

Hey! I Found the ECU! Turns out my mechanic was hooking stuff up to the TCU instead. Don't know how I missed it the first time!

 

Anyway, the black box computer is hooked up and working as promised. Thanks for all the help, and making so much information available online! Could not have gotten this thing working without it!

 

Mike

[Cougar]

Glad you got things going. Thanks for the feedback.