Weird VSS issue.

[Cougar]

I was replacing the instrument cluster because it stopped working due my my alternator spiking really high. And since then my electrical system has been acting stupid, so that probably has to do with it.

 

"Whoa, hold the phone Alice". I think you just called it. The alternator is very likely to be the culprit here. That or possibly bad grounding between the chassis and the battery.

[edrach]

I dug up the wiring diagram for a '95 Impreza with similar VSS and EJ22 engine (and a non-cable driven speedometer). Wire colors might be different, but I think the main connections and wiring is similar enough to your car to help track down the culprit. If you'd like a copy of the diagrams I have (3 pages) I can scan them and send them to your email address.

 

VSS wiring:

 

VSS pin #1: green/yellow wire to pin 10 of the instrument cluster for the speedo and tach circuit as well as pin24 of the B135 ECU plug.

VSS pin #2: black/red wire tied to ground.

VSS pin #3: green/black wire tied to pin 7 of the OBDII connector as well as pin 7 of the instrument cluster (the other side of the speedo and tach circuit) as well as pin 5 of plug B152 (fuse 18 for 12VDC power).

[987687]

Thanks for the info!

One clarification though, I only have 2 wires coming off my VSS. Can I assume what you list as "VSS pin #2: black/red wire tied to ground" is grounded directly from the VSS to the transmission?

[edrach]

Thanks for the info!

One clarification though, I only have 2 wires coming off my VSS. Can I assume what you list as "VSS pin #2: black/red wire tied to ground" is grounded directly from the VSS to the transmission?

I can only tell you what I see in the diagram. It shows 3 wires. If the two wires that you see are green/yellow and green/black then I think it would be correct that the VSS is grounded through the case of the transmission. The diagram shows the ground through a black/red wire.

[987687]

The wires are both black

And they're not just dirty, or something. I cleaned them off, and they're black.

[edrach]

The wires are both black

And they're not just dirty, or something. I cleaned them off, and they're black.

I wouldn't worry about wire color so much. The VSS wires can be any color; it's when they go through a connector and become part of the wiring harness that I would be more concerned about the colors. In any event, the diagram I have is not specifically for your model. But, as I said before, Subaru likely has the same basic wiring for many similar models within a reasonable span of model years.

[edrach]

By the way, I got confirmation that the VSS was a hall effect device. Just another piece of the puzzle.

[987687]

By the way, I got confirmation that the VSS was a hall effect device. Just another piece of the puzzle.

 

It isn't just a reed switch device? Hmm. Since it's a hall effect device the problem could be the vss then. If the signal it's outputting strays uniformly on both ends of the spectrum the gauge would read correct because the digital to analogue circuit on the speedo gauge would still average it out to the speed. The ECU, however, would probably get upset by this erroneous signal and just drop to zero.

This could also explain why last year it did weird things under 20mph after it had warmed up. And this stopped after the alt spike, so the alt could have just messed up the VSS.

 

Does anyone see holes in this theory?

 

 

And for those asking about the alt, it was the regulator. I have a different alt in there now and it works just as it should.

[edrach]

It isn't just a reed switch device? Hmm. Since it's a hall effect device the problem could be the vss then. If the signal it's outputting strays uniformly on both ends of the spectrum the gauge would read correct because the digital to analogue circuit on the speedo gauge would still average it out to the speed. The ECU, however, would probably get upset by this erroneous signal and just drop to zero.

This could also explain why last year it did weird things under 20mph after it had warmed up. And this stopped after the alt spike, so the alt could have just messed up the VSS.

 

Does anyone see holes in this theory?

 

 

And for those asking about the alt, it was the regulator. I have a different alt in there now and it works just as it should.

My understanding from the person I spoke with was that the VSS output alternates between 0 and 5 VDC.

[logic23]

I've run into this problem a couple times.

Everything points to the VSS. If the scan tool is giving you weird reading then its either the wiring or the VSS.

There is only one on the transmission the other sensor is to read the output shaft speed.

It is located on the passenger side by the axle>two wires phase 1 and one wire phase two(manual) on phase two transmissions it looks like a crank/cam sensor.

The signal from all I've seen goes VSS>computer>speedo/tach

[snowscooby]

Have you made any more progress in your VSS saga? I am having pretty much the same problem as you, P0500 codes, stalls, and my car is in limp mode. The only difference is my speedo is cable driven and I just have the one vss in the dash.

[987687]

Have you made any more progress in your VSS saga? I am having pretty much the same problem as you, P0500 codes, stalls, and my car is in limp mode. The only difference is my speedo is cable driven and I just have the one vss in the dash.

 

Then you should follow all the advise people have given me for a cable driven vss It usually boils down to replace the gauge cluster.

[Gloyale]

As I've said in previous posts, my instrument cluster doesn't have anything to do with the signal the ECU gets.

 

Yes it does.

 

And here in lies the problem.

 

The Speedo head takes the signal from the speed sensor. It uses it to drive the gauge display, and also reprocesses it as a simple square wave, and sends that data out to the ECU. (the ECU still reads a simple square wave, which is why you can hook new ECUs up to old reed style VSS in conversions and it works)

 

This can be seen by looking at the Wiring diagrahms. The wires from the VSS to the speedo are twisted and shielded. then there is another wire that goes from there to the ECU. That wire is a simple wire, no twisted pair, no shielding. The signal is not in parrallel, it is in series.

 

Replace the speedo head....it is not converting or passing the signal though properly to the ECU.

[Gloyale]

My understanding from the person I spoke with was that the VSS output alternates between 0 and 5 VDC.

 

that is what the reed style VSS in a cable driven dash does.

 

The later VSS generates an AC voltage.....that AC voltage is transformed into a square wave by a circuit inside the gauge cluster, then the "translated" signal is passed on to the ECU.

[987687]

so I need ANOTHER cluster.... wonderful. at least they're cheap and easy to change the mileage

[2000 Legacy]

Hey 987687,

 

How did you make out with your VSS?

 

The reason I ask is because I have a similar problem (car stalls when the clutch is pushed in when coming to a stop sign or intersection). I posted this problem back in the spring as "2000 Legacy stalls when clutch is depressed", the history is currently on pg. 15 of this forum at the moment.

 

Someone in one of the responses mentioned the VSS as being the problem but I brused it off since the speedometer seems to work fine and since the only trouble codes I have are Cylinder Misfires (P0301, P0302 & P0304 I think).

 

The one thing I have noticed is that the Tachometer drops real fast when the car is going to stall. Please let me know how you make out, I've had this problem for about a year and a half now. Unfortunately its too unsafe for my wife or son to drive.

 

Thanks

2000 Legacy in CT.

[987687]

If you have misfires on 3 of 4 cylinders, you've just found your stalling issue. Fix the misfires and you'll be fine.

And I have not fixed it yet. Although I'm fairly certain it's the cluster causing the issue. I have been away for the last 2 weeks on 3 different road trips, 5 different states, and 2 countries... But sometimes I'm gonna take out the cluster and clean the contacts on all the plugs if they're oxidized. I'm thinking maybe it's a connection issue.

[2000 Legacy]

Thanks 987687,

 

I'm not sure how to fix my misfires, the dealer replaced the Fuel Injectors and that didn't seem to work.

 

Good luck on your problem, please keep us posted. It seemed like we had or have a similar problem, stalling when the clutch is pushed in at a stop or intersection.

 

Thanks

2000 Legacy

[987687]

Thanks 987687,

 

I'm not sure how to fix my misfires, the dealer replaced the Fuel Injectors and that didn't seem to work.

 

Good luck on your problem, please keep us posted. It seemed like we had or have a similar problem, stalling when the clutch is pushed in at a stop or intersection.

 

Thanks

2000 Legacy

 

It doesn't always happen to me though. Maybe 1 in 10 times when it's acting up, which is intermittent. I guess you already have a thread for the misfires, but replacing the injectors is not what I'd do first... Plugs and wires, timing off, coil may be going since it's on 3 cylinders, etc. Anyway, back to my issue.

[2000 Legacy]

Hi 987687,

 

I did the plugs, wires and coil pack (all OEM), checked the Timing Belt, it looked ok. Thanks anyway. Good luck with you issue and problem.

 

2000 Legacy

[Cougar]

Hi 987687,

 

I did the plugs, wires and coil pack (all OEM), checked the Timing Belt, it looked ok. Thanks anyway. Good luck with you issue and problem.

 

2000 Legacy

 

Some folks have cured a misfire problem by cleaning the engine ground connections, and others by replacing the O2 sensor.

[2000 Legacy]

Thanks Cougar for the insight, I'll check/clean the engine ground connections and maybe down the road look at at the 02 Sensor.

 

2000 Legacy

 

PS: 987687, I don't mean to be using your post for my problem. Thanks.

[987687]

So I took my gauge cluster out today. The screws that act as contacts and hold the speedo part in were very loose. That is most likely what was causing an intermittent issue. I hope that fixes it!***

[Cougar]

I hope so also.