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05 Subaru
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Discussion Starter #1 (Edited)
I have an 2005 subaru forester with 82000 miles and the Check engine light is on and cruise control is flashing took it to the dealer and they replace the oxygen sensor after driving the car for about 20 mins the lights came back on.Any ideas on what should I do need help. So I went out and bought an OBD 2 scanner and the code I am getting is p0420-catalytic-converter-efficiency-below-threshold.
 

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03 WRX
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BAD GAS... happens every year (past 3 years) I go skiing up north here in MN, same area gas stations.. I reset it and never comes on after the next fillup.. use SHELL or BP.. avoid Holiday gas..
 

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Went through this last October on my 06 w/ 70K at the time. When tech did your diagnostics, it should have told on your invoice which O2 sensor was bad/dead. Mine did and front/upstream O2 sensor was bad. This was replaced and ECM reset...(they did this right?). Check your paperwork out to verify if this was done and if ECM memory was reset. Good luck,

Motoretro
 

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2010 Forester XT Automatic
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575 Posts
Spend the $50 to buy a OBD2 code reader from Kragen. Once you have the code, come back, that will allow us to narrow down what could potentially be causing the issue. Also, having an OBD2 reader allows you to go the the dealer/mechanic with a semblance of an idea what is wrong with your car. You will be more knowledgeable of what the problems could be, so less likely to get taken for a ride.
 

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2008 Forester
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Spend the $50 to buy a OBD2 code reader from Kragen. Once you have the code, come back, that will allow us to narrow down what could potentially be causing the issue. Also, having an OBD2 reader allows you to go the the dealer/mechanic with a semblance of an idea what is wrong with your car. You will be more knowledgeable of what the problems could be, so less likely to get taken for a ride.
Not to mention you won't get charged a $50+ "diagnostic fee". *sigh*
 

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04 Forester X, MT
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1,039 Posts
advance and autozone read codes for free.

i'm waiting to get me a better ($) code reader that can read info "live" and graph.
 

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2008 LL Bean
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I have an 2005 subaru forester with 82000 miles and the Check engine light is on and cruise control is flashing took it to the dealer and they replace the oxygen sensor after driving the car for about 20 mins the lights came back on.Any ideas on what should I do need help.

I started a thread on SAME problem below.....on my 42,000 mile '08 Forester w/2.5 engine.

Here's what we've experienced: I filled up with gas one day. After driving it down to 3/4 full, same EXACT lights showed up. CHECK ENGINE (solid), and CRUISE (blinking). Next time I filled up, the following day, the lights disappeared. Once again, after about 80-100 miles, came back on again.

This time they stayed on......made appointment w/dealer for a couple days ahead. 2 days before appointment it went out. And for about 4 days now, with yet another fillup......it remains out and normal. So I had to cancel appointment.......since it's like seeing the doctor AFTER the flu is gone !

So here's my personal conclusion (which of course is subject to change):

The problem was PROBABLY caused by the first fillup referenced above....there was one guy pumping, and there were 8-10 cars waiting for gas on this day before a snow storm. He actually failed to accurately tighten the gas cap (which I DID determine after reading my car's manual).

Yes, in the other fillups, it was tightened up.......BUT......and chatted with dealer about this........it DOES take the car's computer system awhile to re-adjust itself completely. If so, in this case it took 2-3 additional fillups for the dumb computer to get the message.

If this changes, I'll get back here to let you know. But for now, this problem is GONE. (p.s., each time it came back, the cruise contrrol worked perfectly, the engine temp fine throughout, oil fine throughout).

Oh.....and as indicated by other members in my post (thanks guys), the CRUISE control blinks EVERY time the CHECK ENGINE light appears, for WHATEVER reason.

So.....for me anyway........living in NJ could be my original problem, since we trust someone else to properly tighten the gas cap........no more for me.....don't want to go through this again.....will be out there in the cold to tighten, then tighten some more after the pumping is done !
 

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Cruise control blinking and CEL on is what happens for any check engine light situation. Any code is going to do that so it really doesn't tell you anything at all. Goto a chain autostore and get the code read for free so we actually know why the lights on.
 

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2008 LL Bean (4EAT)
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BAD GAS... happens every year (past 3 years) I go skiing up north here in MN, same area gas stations.. I reset it and never comes on after the next fillup.. use SHELL or BP.. avoid Holiday gas..
What makes gas bad?
Why would Holiday gas always be bad?
Is there any benefit for a station to be selling bad gas?

Our Buick picked up a whole tankful of bad Shell gas two years ago. It cost $1000 to fix the car, and the station paid for it. And paid a couple of dozen other people, too, according to the letter of apology they sent with their check. And that only included people who traced the problem to that station.

The poor station did not intend to sell bad gas. Water. It was an accident covered by their insurance. Their water alarm did not work. The water apparently came from the independent carrier that brought the gas to them from the Shell depot.

"Bad gas" will do more than make a CEL come on. It will make the engine run bad. Like, miss so badly it will barely run.
 

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05 Subaru
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Discussion Starter #10
So I went out and bought an OBD 2 scanner and the code I am getting is p0420-catalytic-converter-efficiency-below-threshold. What does this mean?
 

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2018 2.5i Premium CVT
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It could mean the cat has gone bad, and sadly you’re 2000 miles out of warranty on it. It happened to me, though within warranty. There are no noticeable symptoms. But there are other, less expensive, things that could also lead to this code.

Yours is not an unheard of problem here. There's a very long (13 pages) sticky thread on the subject at this link.

You need professional help on this one. There's nothing more we can do here but guess.
 

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2006 Forester XT Premium
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Check engine light is on and cruise control is flashing

A little late, but:

We had the CEL & CC light issue 1 1/2 years ago. Subaru in Bryanston, Johannesburg correctly diagnosed the problem as being a faulty spark plug lead. Although I'm frustrated at Subaru S.A. not keeping spares and having to import everything from Japan, they did great work and were always helpful! They (surprisingly) only charged me for the new cable and no cost for labor or continued harassment on my behalf. My car's are like family members...

:)
 

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2006 Forester Automatic
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Just bought my 06 Forester about a month ago. The solid check engine light with the flashing cruise control started a few days after I drove it home. It went away after a few cycles of driving - but it comes back after 3-7 more drive cycles, only to disappear again after several more cycles.

The manual does mention (in the section regarding cruise control) that if the car is started while the button on the cruise control lever is being depressed, the check engine light will come on solid and the cruise control light will flash. So I've been very careful not to press that button accidentally while turning the ignition (which can be easy to do, since its right by your hand when you start), yet it still comes on more or less regularly. I'm betting that once that the vehicle is started while depressing that button, the computer gets goofed up and its just something you have to deal with until you replace the computer, unless you can get it reprogrammed.

Given the number and variety of "solutions" I've encountered over numerous threads tells me that no one knows what causes it, other than reading a code which is probably faulty if the computer programming has a bug. Its probably a mix of repair folks who honestly are looking for a solution, and those that know no solution exists and so can make a few bucks replacing parts and doing diagnostics.

I cant believe no one mentioned the manual's note. That was one of the first things I found.
 

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2018 2.5i Premium CVT
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Absent knowing what the CEL code actually might be, any "solutions" you see here are pretty much just guesses. The first step toward getting the truth is to go to Advance, AutoZone, or some other such place and get that code read.
 

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2008 LL Bean (4EAT)
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Forum wisdom...

BAD GAS... happens every year (past 3 years) I go skiing up north here in MN, same area gas stations.. I reset it and never comes on after the next fillup.. use SHELL or BP.. avoid Holiday gas..
So, "bad" gas does not make the engine run such that you can tell anything is wrong, but does show up with a CEL code.

... have noticed a definite tendency of my '09 running better on no-name generic gasoline than on the big brand names or "top tier" fuels. Strange but true. I don't think the boxer engine likes a lot of fancy detergent additives in the fuel, and since the generic fuels tend to have the bare minimum amounts of federally mandated detergency additives, that may have something to do with it who knows.
So, fancy brand names make the engine run worse than no-name gas.
 

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2002 Forester
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I also want the exact code, since there is a bunch (maybe 20??) O2 sensor related codes, we want to know exactly which one.

When I got a O2 sensor code on my GF's Forester at ~113K miles, I replaced both O2 sensors with new direct fit Bosch O2 sensors and the code hasn't come back in over a year (possibly 2 years now???).
 

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2005 forester auto
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In 2005 sensors tied together cruise and check engine light

Tip about flashing light. Engineers in 2005 decided to tie the check engine light and disable cruise control and cause it to flash so we bring our cars to them sooner and not do anymore damage???? HA! God love the engineers.
Lets just confuse the heck out of the consumer blah blah blah.
Also I was told this is misdiagnosed with the codes often causing people to pay $$$ bucks. You need a really good trust worthy mechanic.

I started a thread on SAME problem below.....on my 42,000 mile '08 Forester w/2.5 engine.

Here's what we've experienced: I filled up with gas one day. After driving it down to 3/4 full, same EXACT lights showed up. CHECK ENGINE (solid), and CRUISE (blinking). Next time I filled up, the following day, the lights disappeared. Once again, after about 80-100 miles, came back on again.

This time they stayed on......made appointment w/dealer for a couple days ahead. 2 days before appointment it went out. And for about 4 days now, with yet another fillup......it remains out and normal. So I had to cancel appointment.......since it's like seeing the doctor AFTER the flu is gone !

So here's my personal conclusion (which of course is subject to change):

The problem was PROBABLY caused by the first fillup referenced above....there was one guy pumping, and there were 8-10 cars waiting for gas on this day before a snow storm. He actually failed to accurately tighten the gas cap (which I DID determine after reading my car's manual).

Yes, in the other fillups, it was tightened up.......BUT......and chatted with dealer about this........it DOES take the car's computer system awhile to re-adjust itself completely. If so, in this case it took 2-3 additional fillups for the dumb computer to get the message.

If this changes, I'll get back here to let you know. But for now, this problem is GONE. (p.s., each time it came back, the cruise contrrol worked perfectly, the engine temp fine throughout, oil fine throughout).

Oh.....and as indicated by other members in my post (thanks guys), the CRUISE control blinks EVERY time the CHECK ENGINE light appears, for WHATEVER reason.

So.....for me anyway........living in NJ could be my original problem, since we trust someone else to properly tighten the gas cap........no more for me.....don't want to go through this again.....will be out there in the cold to tighten, then tighten some more after the pumping is done !
 

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04 Forester Xt
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I have early 04 and cel is tied to cruise flash so your year is off . Not dissing you just the facts

Cheers
 

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2004 Forester XT Premium 4EAT
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CEL and cruise control lights are tied together on all Subies with drive-by-wire throttle, i.e they will occur together on an 04 XT, but not on a N/A 04 model.
 
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