Need help with L Trims
Thread Starter
TECH Enthusiast
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Joined: Jan 2003
Posts: 523
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From: Cape Coral, FL
Need help with L Trims I keep throwing these codes P1153 O2S SLOW 21, P0133 O2S SLOW 11 and P1133 O2S SLOW 11. I have replaced one of my O2's and my O2 reading are about right on at wide open throttle. When I clear my codes my L Trims will read for a few miles then after that they just read 0 all the time with no change. Any ideas what is wrong with my L Trims? Do L Trims run off of the O2 sensors. I just dont get it cause my O2 readings are right on but my L Trims dont seem to be reading properly. Any help will be greatly appreciated. Thanks.
Yes, trim runs off O2 switching. If O2s are too
cold then they just lie there. See also the other
post, re my theory-du-jour on the effect of
drawn-through excess oxygen+fuel at high
overlaps.
If you are seeing the LTFTs with big positive
trims (and stanky exhaust) at idle & low cruise
then sensor heat and/or exhaust effects are
the suspects. If you were to header-wrap the
primaries (except for maybe 3-4" about any
welds) and see this problem go away then it
would be just heat effects. That is a cheap
(aside from aggravation & skin) exercise, you
could do it with tin foil and baling wire just for
a driveway session in the name of science
(see your idle O2 averages & "bounce"
characteristics beforehand, wrap up the
primaries & pre-O2 collector piping and see if
you suddenly get some strong STFT action
and LTFT creep-to-center with "busier" O2s).
cold then they just lie there. See also the other
post, re my theory-du-jour on the effect of
drawn-through excess oxygen+fuel at high
overlaps.
If you are seeing the LTFTs with big positive
trims (and stanky exhaust) at idle & low cruise
then sensor heat and/or exhaust effects are
the suspects. If you were to header-wrap the
primaries (except for maybe 3-4" about any
welds) and see this problem go away then it
would be just heat effects. That is a cheap
(aside from aggravation & skin) exercise, you
could do it with tin foil and baling wire just for
a driveway session in the name of science
(see your idle O2 averages & "bounce"
characteristics beforehand, wrap up the
primaries & pre-O2 collector piping and see if
you suddenly get some strong STFT action
and LTFT creep-to-center with "busier" O2s).
Thread Starter
TECH Enthusiast
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Joined: Jan 2003
Posts: 523
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From: Cape Coral, FL
Should I just get new O2's again? When I clear the codes when i start the car (engine cooled) they will work for a little while then just go to 0. My L trims are always on the negative side. They never really go possitive.
TECH Resident
Joined: Jan 2002
Posts: 754
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From: USA
You need to monitor the PCM and see if it goes to close loop when it should and then once on closed loop if Fuel Learn is ON during NON WOT and OFF when in WOT.
Also check for a airflow or MAFT problem.
Also check for a airflow or MAFT problem.
TECH Resident
Joined: Jan 2002
Posts: 754
Likes: 0
From: USA
Your scanner should have a parameter that reports when engine is in open or closed loop and also another parameter that reports when PCM has FUEL LEARN on or off.
When it is off means PCM is in PE mode and is ignoring the O2s and fuel trims.
You may find that with the errors tripped that engine is staying in open loop.
When it is off means PCM is in PE mode and is ignoring the O2s and fuel trims.
You may find that with the errors tripped that engine is staying in open loop.
