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1996 legacy outback vss code p0500


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33 replies to this topic

#1 Giovara

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Posted 24 January 2011 - 09:23 PM

I have an automatic 96 legacy outback. The code p0500 is on and the speedometer works fine. All the threads I have found about this code seems to state that their speedo does not work and that is not the case with mine. I understand that there are two speed sensors. I was told that one controls the speedometer and the other sends info to the ECU. Im thinking the one that sends info to the ECU is the one I should check. The subaru has a low idle sometimes and seems to hesitate sometimes in the morning. Could this be caused by the speed sensor? P0500 is the only code on right now. Could you also tell me where the sensor Im looking for is located?

#2 Fairtax4me

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Posted 25 January 2011 - 12:23 AM

The FSM for 95 says this about the P0500 code.

AG: DTC P0500
— VEHICLE SPEED SENSOR MALFUNCTION
(VSP) —
DESCRIPTION:
The speedometer system is an electric type; it uses no
speedometer cable and drives the speedometer according
to electric pick-up sensor (vehicle speed sensor 2).
The speed sensor 2 is installed on the transmission. The
speed sensor 2 sends the vehicle speed signal (8 pulses
per one turn of speed sensor driven shaft) to the speed
detection circuit in the speedometer where this signal pulse
wave is regulated.
The regulated pulse signal (4 pulses per one turn of speed
sensor driven shaft) is sent to the speedometer drive circuit
and odometer (trip meter) drive circuit.
The output signal from vehicle speed detection circuit is
also used in ECM, TCM, etc.

The ECM gets it's info from the combination meter.
I don't have the FSM for 96 though so I don't know exactly which wires you need to check for the proper voltage, resistance, etc.

Edited by Fairtax4me, 25 January 2011 - 12:28 AM.


#3 Giovara

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Posted 25 January 2011 - 10:11 AM

Thank you for that info and quick reply? So should I be looking for sensor #1, since my speedo works fine? I think I have located sensor #1 but I wanted to be a little more confident before replacing it since those sensors cost so much. Also has anyone ever heard of a speed sensor causing an intermittent rough idle?

#4 GeneralDisorder

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Posted 25 January 2011 - 10:51 AM

I'm getting the exact same thing on a '96 GT right now. Speedo works fine and idle got a bit lower and the transmission is shifting at strange times.... makes sense since it's having trouble determining vehicle speed (apparently). But according to that FSM info above..... we need to replace the gauge cluster?!?!

Tell me - does your dome light work? I blew a fuse when I unwrapped some e-taped wires from a very naughty radio install by the previous owner. That's when it started doing funny things. I just replaced the fuse (15A the main box under the hood) but then promptly loaned the car out and didn't have time to test drive it. I thought it might be related but then again it might not. Perhaps the radio, some illumination, and part of the cluster is powered from there.... WAG.

GD

#5 logic23

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Posted 25 January 2011 - 11:12 AM

With both of your cars it seems like the speed sensor on the tailhousing of the transmission ( speed sensor 1) is your issue. go to the junkyard and take one off....they don't fail that often ( i've never done one) so you have good odds that it will work.

#6 GeneralDisorder

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Posted 25 January 2011 - 11:17 AM

Interesting - I wasn't aware of the speed sensor back there. I have a spare tranny or two so I'll check that out.

GD

#7 Giovara

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Posted 25 January 2011 - 12:23 PM

My dome light does work. Your the first I have seen that is having the same symptoms as mine though. Please let me know if sensor #1 is the answer. Ill do the same if I find anything else out. Thanks everyone for your help. Much appreciated!

#8 GeneralDisorder

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Posted 25 January 2011 - 12:33 PM

Yes - I'll let you know. This just happened on a car that I'm reconditioning for sale. I haven't touched the tranny except for some ATF changes so it's not likely related to the engine swap I recently completed. Probably just a fluke thing. I should have the car back in a day or two and It will be looked into promptly.

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#9 logic23

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Posted 25 January 2011 - 01:17 PM

yeah their are two VSS. The one by the pass axle is the one that the computer reads for the spedo. It must have some crossover to the running of the car because if it fails the car will idle funny from time to time and throw a CEL code. The rear VSS ( which looks like an ABS sensor) is in the tailhousing (top pass side) and is held in with a 12mm bolt. It should pull right out (its plastic) i think you have to cut the wiring to it because there is no break or the plug is internal which means dropping the pan etc.

#10 987687

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Posted 25 January 2011 - 01:44 PM

I had a VSS issue with my 96 legacy, and although mine is a manual, the cluster should be the same. The gauge was reading the correct speed, but I was getting that CEL and it was going into limp mode. I plugged my scangauge into the car, and the speed on the scangauge was completely erratic, would eventually drop to zero then the CEL came one.
I pulled the gauge cluster out to find what was going on, turns out the screws on the back of the cluster that hold the speedo head in, and that transmit the signal to the speedo head, were backing loose.

How it works, the speed from the transmission goes into the speedo head, shows the speed, then converts to a different signal the computer uses. Why it does this is beyond me, but the screw that makes the contact to the ECU was coming loose causing a flaky speed signal to just the ECU. I tightened it up, and it's been fine for thousands of miles.


EDIT: I was just looking more closely over some of the posts on here about weird idle. After the speed signal to the computer dropped to zero, if I pushed in the clutch to coast down a hill, come to a stop, etc. The engine would just die. So maybe with an auto that could cause funny idle.

#11 Fairtax4me

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Posted 25 January 2011 - 06:19 PM

Thank you for that info and quick reply? So should I be looking for sensor #1, since my speedo works fine? I think I have located sensor #1 but I wanted to be a little more confident before replacing it since those sensors cost so much. Also has anyone ever heard of a speed sensor causing an intermittent rough idle?


Well the FSM references speed sensor #2 specifically for that code.

On MT trans the VSS2 is on the right hand side of the transmission, right about midway front to back of the trans case.
AT vehicle the VSS2 is on the right hand side of the transmission case, about 8-10" back from the bellhousing, near the top of the case.

The input signal from the speed sensor to the instrument cluster is an 8 pulse per second AC voltage signal. The output signal from there to the ECM is 4 pulse per second DC voltage of 5V. The ECU pinouts changed a few times over the years. I don't know if the 95 and 96 are the same, but you can try checking Pin 57 on the ECU connector for a 5V reading while driving. It may be easier to put the car on 4 jack stands and "drive" it in the air than to try and monitor a VOM while driving on the road. Pin 57 is the first pin on the left in the center row on the right half of the ECU connector.

#12 johnceggleston

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Posted 25 January 2011 - 06:38 PM

i would not mess with the rear speed sensor, vss1. it is only used to compare front to rear for the transfer clutch / duty c engagement. (or for the ecu to know the speed if the front fails.) plus it does not unplug, you have to cut and splice.

i would look for a bad connection between the speedo and the ECU. if the screw on the back of the speedo as mentioned above is the problem all the better. but if not i would check / clean all of the connections on the ''perimeter'' of the cluster. they are not your typical wire/ plug connectors. if you have ever pulled an instrument cluster you know what i mean.

but having read the post above about the screw, i would check that first.

if the speedo works, the VSS2 and wiring between the two is ok. the problem has to be after the speedo and before? the ECU.

#13 GeneralDisorder

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Posted 25 January 2011 - 06:43 PM

Is the VSS signal to the ECU one that I can monitor through the OBD-II? I am awaiting delivery of my new OBD-II to Bluetooth adaptor so I can use my Android phone as a real-time monitor, etc.

GD

#14 987687

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Posted 25 January 2011 - 06:57 PM

Is the VSS signal to the ECU one that I can monitor through the OBD-II? I am awaiting delivery of my new OBD-II to Bluetooth adaptor so I can use my Android phone as a real-time monitor, etc.

GD


I have a scangauge. Yes, you can monitor in real time what the ECU is getting for a speed signal. That's why I was saying in my earlier post how I found out where the problem was. I had a good signal to the gauge, but a bad signal to the computer.

#15 GeneralDisorder

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Posted 25 January 2011 - 07:31 PM

Oh! Excelent. I am definitely going to try that out. An excuse to use a new tool! I'm in..... :lol:

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#16 987687

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Posted 25 January 2011 - 07:33 PM

Oh! Excelent. I am definitely going to try that out. An excuse to use a new tool! I'm in..... :lol:

GD


Any excuse to use a new tool!! I love new tools.

#17 GeneralDisorder

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Posted 25 January 2011 - 08:50 PM

Hard to beat $50 + $5 Android app for a complete diagnostics station (wireless and pocket sized even!) with real-time monitoring (assuming you already have the $400 phone of course :-p). That's cheaper than my simple "read/erase" scan tool that doesn't monitor anything!

GD

#18 Giovara

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Posted 26 January 2011 - 10:47 AM

Hey, so I took out my speedo and sure enough there where five screws that hold the speedo head and they were all about a half turn loose, when all the other screws were snug tight. I started her up and she idles perfectly! Ive only driven twenty miles since and the light hasn't come on yet. It use to come on after about three miles. Ill drive it more today and see what happens and report back. This could have been really expensive if I would of given it to a mechanic. Thank you 987687 for your post and everyone else for all your help. This forum is a life saver!

#19 987687

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Posted 26 January 2011 - 10:52 AM

Hey, so I took out my speedo and sure enough there where five screws that hold the speedo head and they were all about a half turn loose, when all the other screws were snug tight. I started her up and she idles perfectly! Ive only driven twenty miles since and the light hasn't come on yet. It use to come on after about three miles. Ill drive it more today and see what happens and report back. This could have been really expensive if I would of given it to a mechanic. Thank you 987687 for your post and everyone else for all your help. This forum is a life saver!


You're welcome. Glad I could help.

#20 Olnick

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Posted 26 January 2011 - 12:49 PM

Wow! Congrats on the fix, Giovara. And thanks for the great information, 987687.

Once again you've shown that USMB is the best resource a Subaru lover can have!

#21 GeneralDisorder

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Posted 26 January 2011 - 04:23 PM

I will find out today or tomorrow if this is also the issue with the '96 I'm dealing with. I will definately report back with pictures.

GD

#22 987687

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Posted 26 January 2011 - 05:47 PM

I have a pic sitting in my photobucket of the back of the gauge cluster from a different project...
Each gauge head is screwed into that back board, the screws hold the gage in place, and give it the signal.

The four that go into the speedo head are the four on the right that are around the black numbers CO92595. Those are the ones I had come loose.

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#23 Giovara

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Posted 26 January 2011 - 08:32 PM

Yeah, those were the same four that were a little loose on mine also the one under the plug was a little loose. I drove fifty more miles today and no light on.

#24 Fairtax4me

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Posted 27 January 2011 - 12:16 AM

Awesome! Hopefully the fix holds up.
This should be added to the USRM.

#25 987687

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Posted 27 January 2011 - 12:18 AM

I could write up my findings in a more consolidated post, to submit.




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