CEL, code P2097

CEL went on last night while driving down the highway. Took it to AutoZone and the checked the code and it came up with code P2097. The definition that they printed off was:

 

Post catalyst fuel trim system too rich bank 1 Probable cause

 

Rich Air/Fuel ratio-Leaking injectors, regulator, high fuel pressure

 

Incomplete combustion - Ignition or mechanical condition

 

Failed HO2S (Heated oxygen sensor)

 

When I asked about th HO2S, she said there were 2 different ones for the Legacy, think she said before and after the CAT. The difference in price was $30 between the two. Does the Legacy have 2 sensors? If it's the HO2S that's bad which one or both bad? The price were $131 and $161 for the sensors. Does that sound right? Would I be safe in driving it for while before I get it fixed? If it's the sensor, would it be covered under any warranty? My Legacy only has 43700 miles and less than 5 years old. Any suggestions on this?

There should be two sensors, Bank1 and Bank2. Judging by the first line of the readout, it's your Bank1 sensor that went out. I would look around online before paying $131+ for an oxygen sensor.

on a 2005 model you have a different cat-pipe section than us 06+ folks. your First O2 is in front of the pre converter and the second one is after the post converter. There is a good chance the O2 is gone bad and not one bank seeing as how it monitors after the collector for both banks of the engine. Shop around for the correct O2 sensor online you should be able to find them a little bit cheaper

Just got a reply from my dealership. They said it should be covered under warranty so I just have to make an appointment.

There is a good possibility it is more in depth than just a sensor I have a car in here now for the same thing a DTC for p2097 and will post up what we find.

So, I should make an appointment ASAP.

The one today was a faulty A/F sensor (upstream O2), but we still diagnosed it according to the service manual. If it is an A/F sensor it is only covered for 3/36k unless you have SAS Gold.

no SAS Gold.

If it is a sensor, again the diagnostic tree in the SM is extensive and can lead to sensors, wiring issues, ECM issues, exhaust, etc, it could be warranty it may not.

Yes take it to the dealer when my car under full warranty when i got a MIL it went right back to First Team Subaru about 8 times actually.

it's the A/F sensor and cost to repair is about $300. Well, I need it done so it's getting done. Not havin cruise really sucks on long drives.

The one today was a faulty A/F sensor (upstream O2), but we still diagnosed it according to the service manual. If it is an A/F sensor it is only covered for 3/36k unless you have SAS Gold.

 

Ok, I've just gotten a P2097 now as well.

 

I've had the front O2 sensor replaced three times now at about 20k km intervals, I believe it was showing P0131 each time.

 

The most recent replacement was about a month ago. The old one came out sooty, which correlates to running rich.

 

I've just gone back to factory exhaust manifold (from borla replicas - I'm going to wrap them to retain more heat etc). I got the CEL on the way to the shop to swap my headers.

 

At the time, it was already exhibiting the rough idle and poorer fuel economy I had each time the last sensors failed. That has since recovered after putting the factory header back on. Perhaps the hotter exhaust has corrected the fouling at the front O2 sensor (what I feel to be the culprit).

 

I'll call the dealership tomorrow. I'm out of warranty but this could be related to the last replacement so I'll see what they say.

Keep in mind there could be other things causing the P2097.

Yah, I'm going to clear the code today and see what happens.

Ok. Keep us posted.

See if this helps Here is the diagnostic tree for you.

 

http://svt4u2try.com/tmp/2097.doc

So, dealer diagnosed it as rear O2 sensor.

 

Their diagnostic flow differed from yours blackfang in that everything was referenced against the rear O2 sensor and not the front.

 

It failed the tree after the voltage reading diagnosis so suggested cure is replace rear O2.

That diagnostic tree is from the service manual. However, if you look further down the tree, it talks about the rear o2.

Service advisor showed me their service manual for the 2005 Legacy - I checked to make sure it was for the P2097 and it definitely referenced rear O2 vs the front for all the initial steps...

Here is one from the Service Manual for a 2005 Legacy

http://svt4u2try.com/tmp/p2097-2005.doc

Do think it's a bad diagnosis perhaps?

We will find out It is tough to say.

So, just a follow-up:

 

I didn't replace the O2 sensor although I did buy one. The CEL hasn't returned. I waited more than a week and it didn't show up... Not sure if it was just the really cold temps that originally caused it or whether the diagnostic process of removing, reconnecting it etc has sorted it?

 

I've put the helmholtz resonator below the airbox back in, put the cleaned Perrin filter back in and the wrapped headers back on and everything looks to be back to normal.

 

Just did a 450km roadtrip yesterday with reasonable speeds on 91 octane and averaged 7.8L/km with reasonable speeds on 91 octane.

 

So, I think my car and the fuel economy is back to normal...

Good to hear.

My P0131 CEL is back...

 

Just had new Iridium IX plugs put in a couple weeks ago, took out my dirty Perrin filter and replaced it with a clean K&N. Fuel economy had been somewhat down for a bit so thought either the air filter or perhaps the rear wheel bearing I just had replaced might have been a factor.

 

Anyhow, picked up the car from the dealer yesterday after having the rear wheel bearing replaced and the CEL showed up last night. Pulled the code today and sure enough, it's the P0131 again.

 

We had cold weather a few weeks ago but recently it's been relatively mild. -5C average let's say...

 

Cleared the code today and roadtripping this weekend so not sure if it'll clear itself up or not.