Cel Reader

[myles]

Hello all, my bug wrx threw up a cel on the way up to wolves on Sunday night in all that rain. Does anyone have a cel reader that i can read my code with this weekend?

[myles]

im on v power. It came on and stayed on. I was doing a steady 60 on the m5, but ive since read that with a sportcat driving easy will sometimes cause the o2 sensor to read the flow out of range due to the faster flow of the exhaust gases. Just need to check its nothing more sinister! It still runs well!

[myles]

only the de-res. It may increase flow enough to push the sensor over the edge. I did use the shell there. All i need is the reader. When you say odb light do you mean the yellow light with the engine pic?

[Vimmy]

Umm isn't that light to say that the rubber band need re-tightening i.e. CEL=Check ELastic, I think that the 'Classics' had the real engines and when the shape changed they put in rubber bands

Wouldn't the fact that now that the higher flow cat is letting more gasses and heat through and at a faster rate that the O2 sensor is seeing slightly cooler air/gasses and reporting a change on the O2 reading. If the original Cat was in place, the O2 sensor is calibrated to read a certain temperature and gas mixture due to the Cat letting it pass through at a predetermined rate and so the O2 output is known. Now that this predetermined rate has been altered its getting confused??

I'm probably barking up the wrong tree, so I'll leaf it to the pro's

[myles]

that is the way i see it too. I am going to pop into wearings by the back gate of camp, he is going to plug in his reader and see whats going on. Ill keep you posted!

[Vimmy]

Yeah that would be good to know what the issue was. I'm looking to go down the Catless/Highflow Cat path when mine totally 'rusts' (with a little bit of help) through so and expect problems such as this to crop up.

I built myself a AFR reader from a kit which displays either the direct O2 sensor (narrowband) output or the AFR value and comes in handy for watching the O2 sensor outputs as it goes rich/lean whilst driving.

[mark1234]

the cel will come on for a problem relating to any sensor not just the o2 sensor or it's readings, the most likely with a high flow cat fitted is the "catalyst efficiency below threshold" but again it could be any sensor at all.

[Vimmy]

Hi Mark, I agree it could be any sensor that's brought it on, I guess reading the slow/fast flashes on the CEL when the 'diagnostic' plugs are connected may give a further indication. If all thats been added to cause this is the de-res pipe, is the system that sensitive to change that other sensors apart from the the O2 pick up the gas flow change?

[mark1234]

it's not the sensors that are faulty it's the readings the ecu is seeing are out of perimiters, it compares the af ratio readings with the o2 sensor readings and it knows because of tables it's programmed with what the efficiency of the cat is. so you speed up the flow which alters the readings i.e it's a bit less efficient and the ecu spots that and throws up a code because it thinks something is wrong.

it's like having an air leak in to the exhaust between the 2 sensors that will give you the same result which on the early sti's was what happened.

bearing in mind this is only on 01my onwards, if you put a high flow cat on a classic you can get away with it as it only has one sensor so theres nothing else to compare it to to monitor the emissions.

subarus are getting more complicated now to the point on the new legacy the clutch biting point has to be set up on the select monitor as does the hand brake and the stroke of the clutch master cylinder, bring back the old school where you could what you like to get more power without the ecu saying you can't!!!

[Vimmy]

Jeepers I didn't think it would be so finnicky (is that a word?) about a small change like that, as you say why have things gotten so complicated, why cant it just be simple. l blame the ozone friendly warriors, no point worrying about inflated exhaust outputs anymore, 2012 and the Mayans are going to get us first

I'll keep to the simple stuff and get back to my soldering glad I have a Classic now, built to last.

[mark1234]

december isn't it 2012 when it all ends according to them! so do you buy xmas pressies or not.......hmmm decisions decisions

[Big 'D']

  mark@cotswolds said:

december isn't it 2012 when it all ends according to them! so do you buy xmas pressies or not.......hmmm decisions decisions

Christmas.......... Bah-Humbug , hey Mark how are you?

Cheers Iain

[mark1234]

hi iain, not to bad i'm flat out at work then plus a bit which is good, but i got to borrow the 3.6l outback last night we had on loan which made up for work keeping me there till all hours!!!

then we have brought a new sti so hopefully i'll get to pdi it and bring it home one night, such a hard life sometimes!!!!

hows the little one doing?

[myles]

P0420 was the code. O2 sensor cat efficiency, latched on and cleared with the reader. Hasnt come back yet, but it was as I and Vimmy suspected.

[Vimmy]

Does that mean no January sales either then?? dang them Mayans for spoiling my fun.

Good to hear that they identified and cleared the fault code, is it possible for it to latch again or was it possibly down to a one off error. Problem with these cars nowadays their complicated and often a fault is due to something else totally unrelated elsewhere. Bless those little flangesprockets

Edited December 5, 2009 by Vimmy

[mark1234]

if you haven't done anything to rectify why the readings are out it will come back on at some point, it depends what type of code it is i can't remember off the top of my head but it might need to detect it twice in the same journey or just once in 2 consecutive journeys.

[myles]

It will come back, its P0420 'Catalyst System Efficiency Below Threshold', due to the free flowing nature of my system, ie. prodrive sportcat, prodrive 2nd cat delete and de-resonated centre section. It was recorded on a long journey at under 3k revs all the way, which I investigated on the good old web and discovered others have had this code flashed up when driving in this manner. Doesnt make sense to me but there you go!