Fault codes P1496 and 1492

[mervington]

I have had my 2004 Forester 2.0 litre from new.   It has still only done 12k miles and has full dealer service history.

 

Last year, the 'warning' light came on.  The code reader revealed P1496 and P1492 - connected with low voltage input.   The car was running perfectly, and always has done since.     The dealer cleared the codes.   However, within a couple of days they returned.   The dealer said to ignore them.

 

Since then either the dealer or I have cleared the codes on several occasions.   However, within a day or two they return.   As I say, the car always runs perfectly.   The emissions are fine. 

 

I am uncomfortable running the car in this way in case another fault arises, and the existing warning light masks that.     I found on one site advice to:

 

1.    Check power supply to EGR solenoid.

 

2.    Check harness between ECM and EGR solenoid valve connector.

 

3.    Check poor contact.

 

That sounds good, but there is a problem.   Whatever causes the light to come on, obviously seems only to do so for the shortest of times.   Thus, a low voltage might never be shown.     Although I have worked on cars since 1964, and did all my own repairs etc, I cannot now because I suffer from Meniere's disease.  It causes extreme vertigo.  Putting my head at angles brings that on.

 

I suggested to my dealer that the relevant connections might simply be disconnected and flushed with switch cleaner.   I thought that might be easy.  However, he has come back to me saying that it would not be possible to do that without removing the inlet manifolds and ancillaries, ie it would take a long time and be costly.    I cannot look properly because of the vertigo problems I have, but I struggle to see why these connectors could not be easily accessible. 

 

I would greatly appreciate advice from members:

 

1.    Generally about the warning light issue.

 

2.    Accessing the connectors and cleaning them.

 

Many thanks.

[wtdash]

P1496 EGR Solenoid Valve Signal #3 Circuit Malfunction (Low Input)

P1492 Subaru - EGR Signal Line 1 Circuit Low

Read more: http://www.engine-codes.com/p1492_subaru.html#ixzz3ptf97TcX

 

Since both are EGR-related, I'd be looking @ the EGR valve. Ensure the Vacuum hose(s) are attached and the electrical connection is connected. I'd UNPLUG it and then plug it back in and check the wires to/from the EGR to ensure they are not broken or somehow damaged.

 

This LINK is for an Impreza (which is nearly  identical in its electronics). He CLEANED his EGR and it helped....try that too.

 

GL,

TD

[mervington]

Many thanks wtdash for your comments.

 

I should have been more explicit.  I am aware of what the fault codes relate to.   However, assuming it is a low voltage input issue, it seems the fault can never last longer than a short time and is erratic.   You cannot readily replicate it.   It can be days before the warning light returns.   The fault is simply then in the memory, not live.   The car always runs perfectly, and there are no emission issues.

 

That is why I thought it worth all the relevant connectors being cleaned.   As I explained, and although I have a full length pit in my garage, I cannot do that any longer because of the wretched Meniere's disease I suffer from.   It has stopped me from doing nearly all DIY including work on the car.   It had seemed obvious to me that cleaning all the relevant connections should have been an important first step.   But my dealer says that would be major work involving removal of the inlet manifolds and ancillaries.    Since I can't literally get my head down and look round the engine, I cannot check that myself.

 

One of my questions was how easy is to access the connections simply for the purpose of cleaning them?   With further advice/information on that, I could go back to the dealer.   I think it is the service manager who has offered the view, not a technician.

 

Further help much appreciated.

[idosubaru]

This code is benign and will cause no issues - if you're that bad off you can't put your head under a hood I would strongly urge you to listen to the dealer and ignore it.

 

If you want to concern yourself with good maintenance - replace the  timing belt - you're over due.  if that breaks the valves and pistons will collide and you'll have huge repairs on your hand.  And your stranded and the car wont' run at all. Orders of magnitude more problematic than an EGR valve.  That's like worrying about the color of the paint on your walls while the house is on fire...one is a non-issue - the other is catastrophic and coming.

 

I would clean the EGR valve and passages out. 

That's simple, easy, and not rare (like "connections" would be rare without any other compelling reason to think so). 

 

Given the fact you're driving so few miles over so long a time - probably short trips, engine sitting for long periods of time - i wouldn't be surprised for something to be gummed up.

 

As for connections - that's rarely an issue unless they've been chewed on by rodents or previous work done, etc.

 

It would be hard to pinpoint connections - particularly since it's intermittent you're not going to find anything obvious and egregious.  And the risk to benefit ratio isn't very good.  You have maybe a 20% chance of finding an issue there....i'd guess 10% or less unless you give us some more history on the vehicle.  You want to pay good money for a 10% chance of sucess?  I doubt it, they're wise to avoid that work.

 

As for the dealer repairing it:

The dealer has a diagnostic flow chart to test those codes.

Clear the codes and see which one comes back first or do both if they're always in unison.

Go through the Subaru FSM diagnostic tree - it's step by step in the FSM - that's what they should do.

Edited October 29, 2015 by grossgary

[mervington]

grossgary - many thanks for that - very helpful.

 

The car has always been fully maintained to Subaru requirements, by the Subaru dealer.  The cambelt and all related components were replaced last year.   That is the second time I have had it done - from new.

 

Although the mileage is very low, it is rarely used for short trips and I don't think there is any suspicion of carbon problems.

 

I can readily accept that the code is benign.  That is not the problem.   What worries me is if in the long term another more serious fault develops which is masked by the light already being on.

 

What still troubles me is the dealer's claim that these thing are hard to get at.   Whilst an official Subaru dealership here in the UK, it is relatively small, most of their work involving several others makes.   I don't actually mind paying to get these things checked provided I had better guidance on whether it is really time consuming.

 

As I have said, the car always runs perfectly.

 

Thanks again.

[idosubaru]

They should be able to run the diagnostic tree.  Check continuity, probably a vaccuum test. 

[mervington]

Thanks for that.   Assuming nothing untoward happens in the meantime, I'll ask them to do that the next time it goes in for service etc.