code58

Lexmex- Since the P1155 only refers to the heater on B2S1 it shouldn't have to depend on a preset ratio should it? When My DIL's CEL came on, the car was in Seattle with my son and DIL for an extended time because of a medical emergency. I talked to some very friendly and accommodating mechanics at an independent Lexus shop and was assured that it would make almost no difference. Went online and did a lot of reading on just how the A/F ratio sensor works and was convinced that the heater doesn't even come into play very much or for very long. Most of the time the exhaust heat where they are placed so close to the exit from the cylinders does the job. The heater was just to speed things up and modulate when needed.

Lexmex

Well, as long as that CEL is on, it's going to have to depend on nothing. Keep in mind, if after about 2 or 3 drives, the light still stays on, you have a problem, but I have had codes, notably the P0171 code, but also a few A/F codes, that I did not turn off via scanner, but the vehicle itself shut off the light, because things had returned to normal (could have been climate, a gas quality issue (particularly in Mexico), but if that sensor indeed has a true problem it's not going to be getting the right readings, and it's going to have to fall back on the ratio.

code58

Lexmex- The CEL will not go off as long as the heater has an open circuit (the most common problem with P1135 or P1155) But the heater is only there to get it into closed loop fast and then it shuts off. The only other time it comes on is when going down a hill with little or no throttle (or a like condition where the normal exhaust isn't warm enough to cause the sensor to read accurately) The rest of the time it's just loafing (shut off) The sensor doesn't have to fall back on default ratio because the exhaust is supplying the proper amount of heat to cause it to function normally. As a matter of fact when My DIL's went bad in Seattle, my son said the only time they could even tell there was anything amiss was for a minute or two after it was started- just ran not quite as smooth. It did not seem to affect the mileage for the remainder of the 4 months she was there or on the 1200 mi. trip home. When the car came home I replaced BOTH the sensors and cut the one apart that triggered the CEL (P1135) and indeed it had a separation in the heater element.

Lexmex

I'd say 80 to 90% of the time that I've had to clear one of these A/F codes, for either bank, I'd note a difference in the vehicle performance immediately after the code was cleared. Some of these open/closed circuit problems can be temporary, reason being that often there is a pending code behind it. I've examined several times where I've had pending codes involving the P113X or P115X variety and then a few days or so later, bang, a CEL light will come on, it's not just the malfunction error, which is separate from open/close fault. Yes, I have seen it come on and not notice any difference before or after, and in other cases it felt like crap. Keep in mind that when we get one of these CELs, we might not notice the affect on MPG because psychologically we might pull back, let off the accelerator, etc., thus the effect may not be as great. However, I can tell from Mexican experience with my lead foot, that the MPG decrease is indeed there if you keep your driving habits the same on a CEL involving the A/F sensor. Over an extended period of time with such an A/F CEL, it's going to have points where there is not enough heat (as you mentioned) and the vehicle is going to have to go into default mode.

There's a fuel additive, actually an enyzme, that I am experimenting with right now to tackle some ethanol related issues (E10) that I have been having in Florida and with this additive has come some A/F sensor issues, expected. I am evaluating some of these issues and will report more fully after a few more tanks of gas.

My girlfriend's Expedition used the same additive and seemed relatively clean of any issue after about 1.5 tank fulls.

JAB

1999 AWD RX300 175K. After resetting the codes several times, and putting some fuel injector cleaner in the gas, I'm still getting P0125, P1133, P1150, P1153, and P1155 codes in various combinations, sometimes shortly after reset and startup, sometimes not until after 50 miles of sustained freeway driving. I doubt that both A/F sensors are going to coincidentally fail at the same time, so I look for a single failure common to both banks that might confuse the OBD wizards. I'm thinking temp sensor and/or thermostat? Or am I wasting my time with my limited insight and tools (the $35 CostCo CodeKey OBDII reader)? Does my independent mechanic have the more sophisticated tools necessary to sort this out, or am I stuck with dealer? TIA.

Lexmex

I am close to either getting a more advanced OBD2 scanner or laptop software, haven't decided since I kind of like having something always handy in the car (as opposed to the laptop method), because I want to be able to check out the readings on both of the A/F sensor banks so I can narrow down the possibilities. When I was in Mexico, I usually noticed climate or some other set of conditions, which would bring on an A/F sensor problem, but as the vehicle gets older I am going to need these tools, which a good mechanic should have.

chenxingha

Is this part for P1150 the same as Denso 234-9009? If so, it is a little over $100 at Amarzon.com with free shipping.