Mikevan10 Posted November 15, 2015 Share Posted November 15, 2015 The speedo on the '97 Legacy 2.2 with manual transmission just suddenly stopped functioning last Thursday evening. Dropped to 0 mph and sits there. Odometer non functional too. I did some searching around the forum and saw several mentions that this would result on driveability issues, engine speed (rpm) limitations, etc. but I am here to tell you that there is absolutely NO other symptom besides the gauge not working and the MIL getting lit up. The trouble codes are P0500 and P1540. My plan is to jiggle the connector at the end of the sensor pigtail. Other suggestions? Thanks, Mike V. Quote Link to comment Share on other sites More sharing options...
ocei77 Posted November 15, 2015 Share Posted November 15, 2015 do search for speedo fix. May be the circuit board on back of unit or loose mounting screws. O. Quote Link to comment Share on other sites More sharing options...
987687 Posted November 15, 2015 Share Posted November 15, 2015 (edited) I had a similar issue years ago, try my repair. http://www.ultimatesubaru.org/forum/topic/115677-p0500-repair/ In my case, the speedo still worked but wasn't sending a signal to the ECU because the associated screw was loose. If your input signal screw is loose none of it will work. Failing that, I believe your car has the two wire variable reluctance speed sensor. For some strange reason I have one of those sitting on my desk, even though I don't own any subaru new enough to use one anymore... I just measured mine, the resistance across the two wires is 389 ohms. Unplug the connector at the sensor and check it with an ohm meter to make sure it's somewhere within say 10% of that reading. If for some reason you have a 3 wire type, I have one of those somewhere, too... I can't find it right now, but two wires should have 12v across them, the 3rd is the pulse signal back to the gauge/ecu. On a 2002 impreza there's a fuse that gives power to the speed sensor, reverse lights, and radiator fan relay. It's marked for none of those things, go figure, but if that fuse blows your speedo and reverse lights won't work. Edited November 15, 2015 by 987687 Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 16, 2015 Author Share Posted November 16, 2015 Thanks for the comments all the way from Northern Maine! I have not done anything yet to troubleshoot my issue but, just to update those of you who were wondering, I drove the car about 150 miles yesterday (mostly highway, some urban) and had absolutely no issue (other than the speedo not working and the MIL being illuminated). So I guess one (or both) of the following is true: 1. The sensor is working fine and its signal is getting to the ECU satisfactorily so the ECU can process that information as required (even though the gauge is not responding) or 2. The speed sensor info is not used by the ECU to effect any of the running parameters. Quote Link to comment Share on other sites More sharing options...
987687 Posted November 16, 2015 Share Posted November 16, 2015 (edited) What you really need to do here is plug in an OBD2 scan tool and take it for a drive, see if it registers speed there. If you don't have one, places like autozone usually scan your car for free. See if they'll let you take it for a drive around the parking lot. That's the easiest thing to diagnose first. I do know the ECU uses the speed signal, my 96 would randomly stall when pushing the clutch in while moving or coming to a stop. Actually my 2000 outback did the same thing when the speedo drive gear in the transmission escaped. The speed signal to the ECU is probably used for emissions control and whatnot. I lived in Center Valley for a while when my GF was going to school, you guys don't get as much snow and cold as we do up here And when it does snow a lot, nobody knows what to do I was down there during that bigass storm 2009 or 2010. Edited November 16, 2015 by 987687 Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 16, 2015 Author Share Posted November 16, 2015 I have a borrowed scanner. I do not know if it will display "real time" vehicle speed. I will look at the manual tonight. I am familiar with Maine winters. I have family near Norway. Thanks, Mike V. Quote Link to comment Share on other sites More sharing options...
987687 Posted November 16, 2015 Share Posted November 16, 2015 I used to live in Svolvaer in the Lofoten islands, winters there make the Maine winter look like a cold snap. Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 16, 2015 Author Share Posted November 16, 2015 I meant Norway, Maine (but we are getting a little off-subject now). Regardless, in my old age I am less and less tolerant of the cold - and I do all of car work OUTSIDE! Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 22, 2015 Author Share Posted November 22, 2015 OK, I hooked up the scanner, which does display real time data. The Vehicle Speed stays at 0 mph (the other parameters do display and change with operating conditions). Does this indicate a faulty sensor and/or wiring out of the sensor? Or does the sensor reading get "conditioned" in the speedometer module before it gets sent to the ECU which could mean the problem is in the speedo and not the sensor? Either way, the fact that the OBDII port is putting out 0 mph suggests to me that the ECU is not getting the vehicle speed, and yet the car runs great... Mike V. Quote Link to comment Share on other sites More sharing options...
987687 Posted November 22, 2015 Share Posted November 22, 2015 The sensors almost never fail, but it's easy to unplug and check the resistance if you wanna do that first. Then pull the cluster and check the screws I mentioned. Quote Link to comment Share on other sites More sharing options...
nipper Posted November 22, 2015 Share Posted November 22, 2015 When you get a bad VSS code, it is usually a failed VSS. Check the wiring. They are simple enough to bench test. They are very low tech sensors. Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 29, 2015 Author Share Posted November 29, 2015 I disconnected the speed sensor and measured the resistance between the two pins in the connector and it is less than 1 ohm. I then tested a spare speed sensor and also got less than 1 ohm. Quote Link to comment Share on other sites More sharing options...
nipper Posted November 29, 2015 Share Posted November 29, 2015 You have to spin it and make sure its making a pulse. Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 29, 2015 Author Share Posted November 29, 2015 And I just drove the spare sensor with an electric drill and the AC voltage across the pins varied nicely with drive speed. The AC voltage varied from zero to over 10 VAC corresponding to the drive speed. This suggests to me that my spare sensor is working normally (even though the resistance seems out of spec). And it also leads me to believe that if I were to remove the sensor from the car I would get the same result (of course, I d not KNOW That at this point) 1 Quote Link to comment Share on other sites More sharing options...
nipper Posted November 29, 2015 Share Posted November 29, 2015 There are 2 failure modes for the spedo. One is failed VSS sesnors. Since this is a manual you have only one sensor. The other is dirty grounds at the back of the spedo (but that wont throw a cel). There is a 3rd but thats a damaged harness which is rare. Quote Link to comment Share on other sites More sharing options...
nipper Posted November 29, 2015 Share Posted November 29, 2015 And one other which is hideous. Rare but ugly, a stripped drive gear for the sensor. Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 29, 2015 Author Share Posted November 29, 2015 (edited) Yeah, I only see the one sensor. I am trying to remove the one from the car but it aint coming out easy. I will try harder but I expect I will round off the hex (using a 17 mm open end spanner). Thanks for the feedback! Edited November 29, 2015 by Mikevan10 Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 29, 2015 Author Share Posted November 29, 2015 So, Nipper, since I am getting P0500 and P1540, you would say I either have failed VSS or failed VSS drive gear (or an issue with the harness between the VSS and the speedo)? Quote Link to comment Share on other sites More sharing options...
nipper Posted November 29, 2015 Share Posted November 29, 2015 It can be redundant since they mean the same thing, and the ECU isnt that smart. Hope for a failed sensor. Quote Link to comment Share on other sites More sharing options...
Mikevan10 Posted November 29, 2015 Author Share Posted November 29, 2015 Swapped in my spare sensor. Speedo is back! The old sensor is clearly shot. You can feel that the drive blade is not driving the pulse generator. Thanks all. Will now clear the MIL codes and hope for the best. Quote Link to comment Share on other sites More sharing options...
nipper Posted November 29, 2015 Share Posted November 29, 2015 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.