87 GL Hatch speed sensor signal?

[SuperNova]

ok, so we have finally finished the swap. We took a CCR EA81 and SPFI off of a 90 Loyale, the car runs pretty good. Now its time for smog and i'm having an issue with hooking up the speed sensor signal wire to the ECU. The manuals i have talk about either a 1 wire or 2 wires coming off the back of the speedo. Well in my car there is 4 wires coming off the top of the speedo. i tried hooking up the yellow/red wire to the signal to the ecu but i still had the check engine light and throughing the speed sensor code. The black ground wire is hooked to a good ground, so for now im stuck trying to figure this out. Any thoughts??

[GeneralDisorder]

Should be a twin pole connector off the top - yellow/red + black is what it was on both the clusters I had in my Brat (85). I grounded the black wire as you indicated.

 

Your speedo does register right? Broken cable?

 

GD

[86BRATMAN]

In my 86 brat, it also had two connectors, one black plug with the y/r and black wires, the other blue with light blue and white wires.

 

I'm not sure what the blue connector does. Best guess looking at what it connects to is that it trips the egr light for its reset. On non feedback carb systems, General correct me if I'm wrong please.

 

Anyways it looks like this...

 

[GeneralDisorder]

I'm not sure what the blue connector does. Best guess looking at what it connects to is that it trips the egr light for its reset.

 

I think that's correct, yes. Every 60,000 if I'm not mistaken. But it's not just feedback's that do that. My 85 had the EGR light on when I bought it. Just have to swap a connector under the dash to reset it. It's a general reminder to clean the EGR valve and check it's operation.

 

GD

[SuperNova]

Yes, the cable is fine and the speedo does register. The pic that 86BRATMAN put online is the same as the one i have. I already tried hooking the speed sensor signal wire from the ECU to it and also grounded the black. Then reset the codes and went for a drive. And when the CEL came on and i checked codes it was still throwing speed sensor. So am i hooking to the right wire? Is the yellow with red stripe the speed sensor signal wire?

[GeneralDisorder]

Yes, but your speedo head could be broken. Put a MM on it and see what registers as you drive. It's an on/off signal (square wave) but a simple MM will show if it's doing anything at all. Should fluctuate between 0 and a few volts.

 

GD

[yegoshin]

I don't have the manual in front of me but this I know.

 

If you measure the resistance with a MM it will fluctuate between 0 and some number. The quicker you drive the higher fluctuation frequency you will see.

 

Thus I belive that the sensor wires need to be connected like this:

 

A -> ECU

B -> ground OR 5volts depending on what the ECU wants.

[SuperNova]

I don't have the manual in front of me but this I know.

 

If you measure the resistance with a MM it will fluctuate between 0 and some number. The quicker you drive the higher fluctuation frequency you will see.

 

Thus I belive that the sensor wires need to be connected like this:

 

A -> ECU

B -> ground OR 5volts depending on what the ECU wants.

 

Yes, i pretty much knew that. My problem is hooking to the right wire (yellow/red??) to the ecu. Since the manuals i have only mention 1 or 2 wires coming from the top out of the back of the cluster, and my cluster has 4 wires. Like in the pic that 86BRATMAN provided. Hopefully the yellow/red wire is the right one, i've just been to busy lately and haven't gotten around to tearing apart the dash again to test the wires and check the speedo cable. There is also only one wire that hooks to the ecu, not 2. And am i supposed to be testing for resistance or voltage?? But as soon as i get time im going to figure this out and ill post an update.

[86BRATMAN]

You've got the right set of wires, the yellow/red and black on the black connector are speed sensor. Like you said you speedo works. So it sound like the problem is in the power supply.

 

This is just a theory here. Feel free to elaborate if you have an idea where I'm going.

 

Ok, Subaru uses yellow/red stripe wires as the power imput for its wiring systems, almost asuradly throughout the years. Should that one not be hooked up to some sort of power supply of X volts, and then the black one would be left to be the signal wire to the ecu.

 

Does that make sense to anybody else?

[SuperNova]

You've got the right set of wires, the yellow/red and black on the black connector are speed sensor. Like you said you speedo works. So it sound like the problem is in the power supply.

 

This is just a theory here. Feel free to elaborate if you have an idea where I'm going.

 

Ok, Subaru uses yellow/red stripe wires as the power imput for its wiring systems, almost asuradly throughout the years. Should that one not be hooked up to some sort of power supply of X volts, and then the black one would be left to be the signal wire to the ecu.

 

Does that make sense to anybody else?

 

OK, so the wire that needs to go to the ecu is the black?? And the yellow/red wire is power to the speedo or coming from the speedo? Well, it makes sense but why would the conversion manuals both say the yellow/red needs to go to ecu?

[86BRATMAN]

That part I don't get either. I was just throwing out another opinion. It would help if somebody had a feedback carb, or cruise control car that wouldn't mind tracking down the wires. Neither of which do I have.

[GeneralDisorder]

I used the yellow/red to the ECU, and the black to ground and have never had a speed sensor code go off. Black is always ground in almost all electrical systems, and the signal wire does not require a seperate power supply as the speedometer signal generator is an electro-mechanical pulse generator. It creates it's own small signal voltage by passing a magnet near a coil of wire. That's why it's such a small voltage.

 

I also have factory CC on my 84 wagon, and black is grounded through the CC unit. It's all in the wireing diagram of the FSM for the CC system.

 

GD

[SuperNova]

I used the yellow/red to the ECU, and the black to ground and have never had a speed sensor code go off. Black is always ground in almost all electrical systems, and the signal wire does not require a seperate power supply as the speedometer signal generator is an electro-mechanical pulse generator. It creates it's own small signal voltage by passing a magnet near a coil of wire. That's why it's such a small voltage.

 

I also have factory CC on my 84 wagon, and black is grounded through the CC unit. It's all in the wireing diagram of the FSM for the CC system.

 

GD

 

OK, well thats what i thought the whole time and thats what i did before but it still threw the speed sensor code after i cleared memory and drove. I'm going to try it again, see what happens. If not, what do you think about swaping the 90 Loyale speedo into the GL cluster? I understand that most older subaru speedo pods are interchangable.