3.0 Legacy R 2004, The engine malfunction  light (MIL) comes on for  a few hundred miles and then goes off for a few hundred miles- performance and emissions  unaffected whether it's on or not.At present it's having an ON mood. I have tried disconnecting the battery overnight and draining residual charge by pressing brake pedal  and horn for a minute, but when  I reconnect  the MIL is still staying on. Any ideas a) what's causing it ? b) any tips for cure? 3) any tips on how to simply get the MIL light off and reset?

 

 

The MIL is telling you that one or more sensors is out of parameters and for long-term peace of mind, and to cure the fundamental problem, you need to know what codes are stored. If you don't, the error warning will continue to occur. The problem needs resolving at source. Also, MIL tripping is cause of MOT failure.

If it is on because something is unplugged for example, you could try to reset it and it will come on straight away.

On some cars you can have codes already stored in the ecu without turning on the light, but the light will come on after certain conditions are met long term.

On mine, I don't know if a wire was loose or not, but when my o2 heater wasn't working like it should, the MIL wouldn't even turn on when ignition lights are on, then after awhile would come on and stay on, with a code stored all that time... don't think it's the bulb playing up, maybe it was programmed to do this to say it has detected a problem but is not quite sure yet?

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Whereabouts are you? Maybe someone close by has a code reader you can use and go from there. With mine I can also clear the codes using the reader

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John - no need for code readers. You have an on-board diagnostic set up on yours.

 

Open the fusebox.

Reach your hand in and feel around above and slightly to the left for the wiring loom.

You'll find two white connectors taped to the loom. They each have a single wire.

Connect them together (they're the only single pin connectors in the area, so don't worry about them not being the right ones).

Now turn the ignition on and whilst the speedo/rev counter needles are doing their sweep, press the trip counter reset button once.

 

The trip counter will now show engine fault codes (eg P0402) or P---- if there are none.

If you press the trip counter reset button it'll show transmission fault codes, or P---- if there are none.

If you press the trip counter reset button again it'll show chassis fault codes (eg C0042), or C---- if there are none.

If you press it again, it'll go back to engine codes.

 

When you're done, switch off the ignition, disconnect the connectors and tuck them up out of the way again.

 

Edit - what i should have added - if you choose to do this, find the code and either post up on and here and I'll find it or search in google as there are plenty of guides on line to interpret these.

Thanks, what worries me about going to a main Subie dealer is they'll want serious money for what is a bum wire if only I can trace it. .   Mark D. Yes rather like your  story ,  I really suspect it is simply  a poor  electrical  connection somewhere. Daz-RSK  Wow, thanks I'll have a look at the fuse box and see if I can identify the wires you speak of.I notice that the drop down flap of the fuse box has fixed on the inside a numerical light panel about 2 cms widex  3 cms long.... I was wondering what this was for ... is it another built in code reader? 

The key pad inside the fuse box cover is for the alarm.

Thanks... so many electronics even if it is 12+years old!

Local garage  got 2 readings today on scanning ; P0420  and C0033 and have reset it... thus at present all hunky dory and no idiot lights showing. In view of age and value of car (£1500 tops) whats the consensus  view of what  if anything should be done? Thanks everyone.

P0420 means Catalyst system efficiency below threshold. Doesn't necessarily mean the cat is bad as there are a number of possible causes including exhaust leaks, bad fuel, misfire, dodgy sensor/s etc. I don't know the chassis code, could have connections to speed sensor.

You'll need to figure out if you like the car enough to invest some time and maybe cash figuring out the wrinkles (which any replacement used car could come with anyway).

Yes, the chassis fault is your VDC (Vehicle Dynamics Control). That's your anti skid system - basically, your traction control. There is a solenoid that is playing up.

C0033 says Front Inlet Solenoid Valve LH Malfunction in VDC.

Unfortunately, unless you are extremely lucky, eliminating the codes at the garage only fixes the symptom, not the cause and it is likely to come back again under provoked conditions.

 

 

Thanks everyone, great forum!