DTC P0135, 0155, problems with 02-sensor heater
Thread Starter
Staging Lane
Joined: Mar 2008
Posts: 57
Likes: 0
From: Stockholm, Sweden
DTC P0135, 0155, problems with 02-sensor heater I got the P0135 and 0155 DTC which indicates problems with the O2-sensor heater. I have checked the bias voltage with cold enginn. It is aprox.450 mV and it is not changing over the time. As I understand I should check the fuse for the heating circuit but I canīt find it !!! Acording to the electric scheme for my engine (Cadillac Escalade 2002, LQ9) there is no fuse for the front O2-sensors (Sensor 1) or have I missed something. I should point out that the engine is swaped into a Firebird -68.
Anyone who can help me ?? Regards / Magnus
Anyone who can help me ?? Regards / Magnus
I didn't even look at the DTCS. The issue that I see with LTs are insufficient switching at idle, though that is a heat loss issue.
Pull the O2 connector, turn the key to on, and check for 12V that powers the heater. On an F-body, connector terminal C is grnd and terminal D is the +12 for the heater. Grnd wire is black and +12 for the heater is pink. I don't know how much different your harness may be, but if you ground one lead of your meter to the chassis and you don't find +12 on one of the 4 wires in your harness's connector, then you know the circuit feeding them is bad. If you get persistent errors from both sides, the circuit feeding them is certainly suspect.
Pull the O2 connector, turn the key to on, and check for 12V that powers the heater. On an F-body, connector terminal C is grnd and terminal D is the +12 for the heater. Grnd wire is black and +12 for the heater is pink. I don't know how much different your harness may be, but if you ground one lead of your meter to the chassis and you don't find +12 on one of the 4 wires in your harness's connector, then you know the circuit feeding them is bad. If you get persistent errors from both sides, the circuit feeding them is certainly suspect.
Because the sensors can't retain the same level of heat that they are designed around when in stalled in headers vs. a cast iron manifold that is closer to the exhaust ports on the head.
450mV is where the PCM will force the O2 sensors
when they fault out. Heater code is just what the
PCM calls it, when they don't start switching soon
enough for its liking.
One thing to try is, moving the closed loop enable
temperature up closer to your minimum hot ECT
reading, not the 140F or so that is commonly set.
If you can make the PCM not look until the thing is
good and hot, maybe it'll get better switching and
not be so bitchy.
Or not. Sometimes bitchy is genetic.
when they fault out. Heater code is just what the
PCM calls it, when they don't start switching soon
enough for its liking.
One thing to try is, moving the closed loop enable
temperature up closer to your minimum hot ECT
reading, not the 140F or so that is commonly set.
If you can make the PCM not look until the thing is
good and hot, maybe it'll get better switching and
not be so bitchy.
Or not. Sometimes bitchy is genetic.
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TECH Regular
Joined: Aug 2006
Posts: 450
Likes: 1
i hAVE the same codes on my car i see that everybody is saying that its because longtube headers, i have long tubes and no cATS is this going to affect my performance, i have p0135,p0140, p 155,p0160, p1153, i just got all these codes i dont know how these will affect performance and if i need to change anything
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i could be wrong, but i think it will make it run a little rich and may affect gas mileage? I just threw P0135 today... again. i throw it about every couple weeks, i get it deleted and its good for another couple weeks. i have longtubes too. i just changed the o2 sensor and thought that would fix it. this sucks.
Teching In
Joined: Oct 2009
Posts: 13
Likes: 0
From: Newnan, Georgia
my 5.3 is doing the exact same thing! i am still running manifolds though. maybe i mounted my bung to far from the manifold? I don't mean to thread jack, its just these symptoms sound all to familiar.
