I drive an 02' wrx, stock cept for stage 1 exedy clutch and streetlite flywheel. I've been having CEL's since 04', had them checked (this was before the clutch/flywheel install), and they replaced a knock sensor...one month later the check engine light is on again. I hadn't taken it back, being that the car seems to run fine, and I'm 80 miles from a Subaru dealer, or one of those places that offers to read codes for free. (in this instance, living in the sticks sucks). On a side note, the CEL usually goes out when I am driving highway miles in southern WI, sipping up that yummy 94 octane that doesn't seem to be available around here. I was planning to get an AP this last month, but a hidden pointy rock to the sidewall dictated that I get tires instead . I'm kind of debating buying just a code reader, so I can get rid of the CEL's before doing any mods, (or at least know what I'm up against). Long story short: Should I get an OBD reader now, or just wait till October when the AP will be budgetable, and read codes with that?
Yeah, I've seen a couple in the low $100's, "deluxe" models for about $200, and one that will log some engine paramaters (didn't see what) for $300 something, that one was in a craftsman catalog. Hadn't got around to checking ebay yet, which is where my OBD reader would end up once I get an AP.
Picked one up today at wally world, for about 105 after taxes... Turns out I am having a PO420, cat effeciency, bank 1 Note that I haven't modded my 02' WRX's exhaust (yet) How would I go about testing to see if it is a faulty sensor?
99% chance it is the sensor. I would just buy a new sensor and put it in. If you really feel the need to test it swap the front and rear O2 sensors and see if the code moves in a few days.
Pardon my noobiness, but I take it that means they are both the same sensor? I would love if someone link slapped me to a page that explained where the sensors are, I gather rear one for is in the DP? , and I would imagine the front one would be the UP? I was reading in some searches that this would usually fall under fedaral warranty to 80K miles...my OD has 79920 on it...doubt I could make it to a dealer before it turns 80K:roll: Thanks for the help, Brian
the sensor wouldnt be... cat would be.... but usually what makes the sensor / cat bad is other issues.... like fuel or lack thereof.... I say do the 02 resistor mod.... Ill see if I can find the pic on my pc
Both the front O2 sensor (found immediately prior to the uppipe in the exhaust flow) and the rear (found in the midpipe) are the same part. However the front O2 sensor is used to determine AFR so the ECU can determine fueling/spark/air while the rear is used only for emissions (Are the DP/MP cats working properly?). Same part, different functions.
Front o2 and rear o2 are not the same part. Different part numbers rear o2 is way cheaper than the front o2 I believe the front o2 is a narrow wideband, or something like that.
He is correct and I was incorrect, for a WRX they are different part numbers. Front is 22641 and the rear is 22690. I don't think you can switch them and have it work correctly. Since it is either the rear O2 sensor or the cat, I'm with WRXboy2003 on doing the resistor mod. Otherwise it'll be $115 for a new sensor or $500 some for a new cat.
Cats.... lol Get a tune and disable the CELs on the rear o2 sensors. Cheaper + more power. I love my Stg 1 tune.
Thanks for the tip, but I think I will just wait till I can $wing stage 2, not really enthusiastic about paying for a tune with a cat that may be bad in the system.
2 more codes came up, right after filling the tank. Misfires on cylinder 2+4. Car runs good 99.9% of the time. Had two times in the last year that it died on me. Once, last year this time, I was on the freeway, took an exit, stopped at the light, then after I got going, it was like the accellerator pedal was not working, the car just revved down smoothly till it died. Started right back up on the first try. Made no obvious noises. Just before getting the OBD reader, I had the car die when pulling out from the gas station, started off the same way, with the car smoothly revving down, till it got to about idle speed, then it sounded like only 1 or 2 cylinders were firing, reminded me of my dad's john deere tractor warming up, the car then died, but once again, started just fine. In 04' with 43 K on the odo, I took it into the dealer for a cel, and they replaced a knock or camshaft sensor...the car was still running fine. In a search, I read that a member replaced a front 02 sensor to fix a similar problem (though it is usually suggested to check the coils and plugs). Being that the previous CEL was for cat effeciency, could this possibly be my problem? (bad sensors) Plugs were replaced about 10-15K miles ago.
do you have any cats left in the car??? most likely the sensor but if you havent taken care of the cat then it is gonna keep being a cycle of chasing your tail replacing parts...
All due respect, and I really appreciate the advice, but wouldn't removing/replacing the cats (without knowing for sure if it is the sensor or the cats) be one of the more expensive ways start to this viscious cycle? The car is stock, cept for exedy stage 1 clutch and streetlite flywheel. Would love to just drop the cats, with a high flow one in the downpipe, but would really like to see the CELs go away before doing any mods...the main reason I invested in the OBD reader. I'm guessing (very green mechanic, change my own oil, plugs, diff lube, filters, and that is about all I have done on my own so far) judging by my search results that I should: Figure out how to test the 02 sensors Figure out how to test the coils Inspect the plugs do a compression check (hoping this comes out fine, this summer has been rough on the credit cards as is). Really want to learn how to do this on my own, I very much appreciate all help and input.
ok... heres what happens... usually car runs rich or lean.... either due to cat inefficiency or other issues (vague) then the sensor burns up... gives code.. so people replace sensor but the cat (if the problm) is never touched, then you go around and around.. this is a very very vague answer as it can be any number of issues causing the sensor to burn out.. I am merely saying if it is the one behind a convertor and all you do is clean or replace it then what is being done about sorting out what is actually causing both the conv' and sensor to fail (usually a fuel related issue) yes replacing a convertor is an expensive job, so is throwing sensors at it if that isnt the problem (seeing that a sensor usually dies due to another issue to cause it too) i wasnt offering replacing the cat as a 'SOLUTION' just highlighting the point that most people throw parts at a car cause a code says XYZ but what caused that part to fail...??? like what you have done or stated at the end of last post.. you seem to be doing the right thing.. reading, researching and asking questions... I am merely coming from the point of view of owning a repair business for the last 3 yrs and dealing with these sorts of things daily... sometimes there is never a plain and simple answer... heck we tried over about a 18mth period to sort out misfire issues on a friends grand am.. my tech of 25+ yrs threw parts at it (which pissed me off eventhough the codes told us it was the 02 sensor) and after replacing the 02 sensor it run like a dream................. for about 2 weeks then showed the same symptoms again... hell the code told us rear 02 below efficiency threshold (similar to your code), guess what it ended up being.... after changing coilpacks, plugs and wires.... and numerous other things... it was a dirty valve!!!!!!! Guess what else.... You drive an 02 WRX whihc have shown many issues with burnt valves due to poor gas ie Holiday etc.... so it could be valves... welcome to Cars
Just thinking out loud here... A bad valve could likely cause both CEL's, right? I'm thinking by dumping the fuel out of a bad exhaust valve during the compression stroke, the cat(s) may not be able to burn off all that fuel, hence the cat ineffeciency alarm? Going to go search now and figure out how to compression test...
try seafoam... heck if your valves are bad that wont work but it wont hurt in case its just some clogging or build up on them...
That was my next idea, after I found out kind of plugs are in the car. I doubt it is a burnt valve, if it is running fine 99% of the time, like he said. I hope that it is just some carbon build up on the valves, which seafoam should take care of. It could also be a bad front o2 sensor, that's not setting a code, but causing the car running rich, setting the 420 code. The only thing is, it's hard to diagnose cars over the Internet.
