O/T Suby question......

[Unclefester]

Something peculiar (well it would be, wouldn't it) happened to our Suby Outback today and I wonder if anyone has any ideas about this.

 

What happened was the speedo stopped working and I think at the same time the "Check Engine" light came on!

 

I can't see any reason why these should be connected, but I'm pretty ignorant about Subys and how they function.

 

I tried the cruise control to see if that still worked and it didn't, so I assume it's the sender unit that's died, rather than the speedo head itself, as, following my (warped?) logic if the speedo head was knackered, the cruise would still be reading impulses from the sender, which I imagine is gearbox mounted.....

 

 

Any Subaru experts out there know about this?

 

 

Lucy in the Sky with Diamonds..ooooh hooo hooo!!...

😬 😬Abbey Road Time-Machine *eek*

 

[CageyH]

Does it not work off an ABS sensor which gives the wheel rotational speed?

 

Only dead fish go with the flow....!

[Unclefester]

I dunno, that's why I asked!

 

Are you just guessing or do you actually KNOW this? 'Twould make life easier if it's a wheel based sender unit.....

 

Of course, the vastly expensive "Owners Handbook" gives, as always, absolutely zero useful information.

 

It's written by idiots and translated by folk with learning difficulties and no sense of organisation.....a very irritating waste of tree.

 

Lucy in the Sky with Diamonds..ooooh hooo hooo!!...

😬 😬Abbey Road Time-Machine *eek*

 

 

Edited by - Unclefester on 28 Jun 2007 23:16:44

[Julian Thompson]

I am pretty certain that this isn't quite right. The wheel speed sensors on each wheel feed the ABS unit and just give a sawtooth wave.

 

I am almost certain (depending on model my memory might not be serving me right!) that there is an electronic gearbox speedo output independant of the ABS system. If you think about it how many of those Subaru's have you seen with a cone filter sat where the ABS unit "could go" if it were optioned - answer - loads.

 

Generally, on Subaru's this sensor feeds the ECU in a shielded cable and the output data is then sent to the clocks via (again my memory here) a green wire (could be green black) in the back of the instrument cluster.

 

If you get your AC voltmeter and earth one end of it and probe the green (or green black) you should get the meter reading corresponding to speed. If your meter has Hz then this is even nicer.

 

If this does not work then repeat the test in the gearbox itself - not fun to be honest as you'll have to rig a test wire setup to check the sensor as you drive. If you have a scope all the better (I think it's a sine wave on there rather than the ABS sawtooth) but again, if not use your DVM.

 

Sounds almost certainly like sensor failure to me.

[Unclefester]

Thanks Julian,

 

that gives me a point of departure.... 😬

 

Lucy in the Sky with Diamonds..ooooh hooo hooo!!...

😬 😬Abbey Road Time-Machine *eek*

 

[Jason Plato]

speedo stopped working and I think at the same time the "Check Engine" light came on!

 

I tried the cruise control to see if that still worked and it didn't,

---

 

were you at a standstill with the ignition OFF at the time

 

here is C7 TOP

Taffia Area Rep

[Tom_C]

We had a test drive in a 2nd hand scooby Legacy once with a flat battery. This was jump started, but wasn't charging sufficiently, and the instruments died randomly duing the drive, so might be worth checking your battery state and/or alternator?

 

We didn't buy the car BTW...

 

BTW please give generously to Bundle's Big Charity Walk for Asthma research here Ta.

 

Cheers

 

Tom

 

FH54WLX

 

see here - UPDATED again

[Unclefester]

Tom,

 

Battery is only 2 months old....alternator is fine.

 

It seems the check engine light comes on when something is wrong with the antipollution kit, according to the wonderfully useless Handbook.....

 

I think I may just drop this on the Subaru dealership!

 

Dave, you are right, it holds perfect speed with Cruise Control when its stopped....even better, when its on axlestands with the wheels off!

 

Lucy in the Sky with Diamonds..ooooh hooo hooo!!...

😬 😬Abbey Road Time-Machine *eek*

 

 

Edited by - Unclefester on 29 Jun 2007 12:50:55

[MartinWoodham]

the CEL comes on for any one of a number of reasons, it's just indicating the presence of a fault, the delear diagnostics (Select Monitor)will tell you what the fault actually is.

 

for the 2 litre turbo engine in 2002 (from my impreza CD) there's a front speed sensor mounted in the gearbox, manual transmission, and the auto version ( manual covers all markets...!) has a front and a rear, again both in the box.

At the ECU, 'Vehicle Speed Signal' is connector B135 (the middle of the 3 sockets), pin 24, and is a 5 volt waveform, by the time it gets to the ecu I'd expect it to be a rounded off (ie slightly lowpass filtered) squarewave.

 

There's a (low) chance that the ECU is the same as a 2l turbo, and a slightly higher chance that the pinouts are the same. If you don't have a 3 plug ecu I'd try a post on the legacy forums and see if anyone has an answer.

 

Martin

Aero'd supersported ex-Roadsports B...anyone got a cheap LSD?