stupid CEL!!
Thread Starter
Melting Slicks
Joined: Jun 2005
Posts: 2,146
Likes: 1
From: Atlanta
stupid CEL!!
ok so for the past couple weeks I have had a CEL code that keeps popping up. it says SYS TOO LEAN BANK1 or something close to that. I can drive the car and sometimes it comes on and sometimes it doesnt...just seems very random. car seems to run fine but occasionally the idle is a tad rough. anyone have any ideas? im stumped on this one
Safety Car
Joined: Sep 2007
Posts: 3,502
Likes: 82
ok so for the past couple weeks I have had a CEL code that keeps popping up. it says SYS TOO LEAN BANK1 or something close to that. I can drive the car and sometimes it comes on and sometimes it doesnt...just seems very random. car seems to run fine but occasionally the idle is a tad rough. anyone have any ideas? im stumped on this one
Tech Contributor
Joined: Mar 2003
Posts: 12,094
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From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
If you did even simple mods like an air cleaner or headers, you need to retune. Your tune is off either way. Running lean at part throttle makes you overly rich at wide open throttle. Running this way isnt good for longevity.
Your profile says you have a superchips tune and those canned tunes cant and dont work. My car had some big tuning changes just going from one brand of header to another. You need a real tune.
Your profile says you have a superchips tune and those canned tunes cant and dont work. My car had some big tuning changes just going from one brand of header to another. You need a real tune.
Thread Starter
Melting Slicks
Joined: Jun 2005
Posts: 2,146
Likes: 1
From: Atlanta
i would like to get a real tune but dont really have $500 to pay for it right now. I havent changed anything on my car in the last couple of years and it has just recently started doing this. thats the part i really dont understand. i guess the O2 sensor being bad is a pretty good possibility
Safety Car
Joined: Jun 1999
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
If you did even simple mods like an air cleaner or headers, you need to retune. Your tune is off either way. Running lean at part throttle makes you overly rich at wide open throttle. Running this way isnt good for longevity.
Your profile says you have a superchips tune and those canned tunes cant and dont work. My car had some big tuning changes just going from one brand of header to another. You need a real tune.
Your profile says you have a superchips tune and those canned tunes cant and dont work. My car had some big tuning changes just going from one brand of header to another. You need a real tune.
When the the air fuel ratio in closed loop varies more than 25% from stoichiometry, that will trigger the CEL. At WOT, the PCM ignores the O2 sensors and switches to a set of fixed tables (open loop) to provide fueling calculation at various RPMs and loads.
However, the PCM will still include the last LTFT % error correction until it returns to closed loop. So at WOT, you could be so off the correct a/f ratio to cause engine damaged not to mention the impact to power.
While the Long Term Fuel Trims can compensate while in closed loop, but the experts advise to keep the % error to less than 0 to -4% in closed loop. The last scan I ran on my car it was under 0 to -2.5%.
Check for leaking vacuum hoses or a leak in the exhaust system ahead of the O2 sensor. If that does not fix it, have someone to tune it correctly on a Dyno. Its worth the cost many times over.
Last edited by Mez; Aug 22, 2010 at 07:21 PM.
Safety Car
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Safety Car
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
In the old days, we would squirt engine starting fluid around the joints of the carb and manifold. The RPM would go up suddenly if it got sucked into the intake.
Today, I hear some use unlit propane torch. If you do that, make sure you do it outside or you may get a BOOM!
Thread Starter
Melting Slicks
Joined: Jun 2005
Posts: 2,146
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From: Atlanta
thanks a lot everyone for your advice. I went hunting for a vacuum leak with my eyes and a propane torch (unlit) but wasnt able to find anything. all hoses are in good shape and connections seem solid. the only thing i did find was that the positive battery terminal was pretty heavily corroded. shame on me for not noticing it but I was out of the country for about 5 months and couldnt keep up with everything. anyways i cleaned it and put some diaelectric grease on it and maybe that will help out some. i know how electrically sensitive these cars are. next time i drive it im going to data log long term and short term fuel tables to see if ther is a difference between the two banks since i only get the CEL for bank one. will update soon.
Thread Starter
Melting Slicks
Joined: Jun 2005
Posts: 2,146
Likes: 1
From: Atlanta
ok great today while driving home the CEL turns on again. surprise surprise. when i got home i scanned it and this time the code was oxy sens circ bank2 sensor 2. WTF?? both of those sensors are brand new. this is really starting to bother me.
Melting Slicks
Joined: Mar 2007
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From: Santa Barbara CA
That would be the post-cat sensor for bank 2 then?
Safety Car
Joined: Jun 1999
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas