I have a Toyota Camry LE (4 cyl; automatic, 5S-FE) 2001 (1/30/2000 delivery date) with 123K miles that has baffled every mechanic it's been brought to- even after having 4 different computers hooked to it. But first my immediate problem:

I have that vague P1135 error code and wonder if a noob like me could fix it. How do i find out if the fix really requires replacing an O2 sensor (and if so where do i get a Toyota Camry O2 sensor?) Are there easier/cheaper fixes to try before that? I'm under the impression that the Air/Fuel ratio sensor is just a fancy O2 sensor with a heating element in it.


The Check Engine light came on Saturday night after some quick driving up the steep & winding hills of Ithaca. A Sunday visit to AutoZone's for their free status checker found only a p1135 error: Manufacturer's Air / Fuel Control. The guy there said an O2 sensor problem was apt to turn up more than just one error code, so he thought my O2 sensor was probably OK. (Is this typical?) I checked the air filter- it looked fine. I found chewed pumpkin seeds and sandy debris under the filter and vacuumed it out. I had rodents up in there and wonder if fine hairs could have slipped through the filter. [I bought the car used in Oct. 2006 with 92K miles (it's my first-ever car!!) and as far as i can recall since i bought it, never had the air filter replaced- it's aways stayed clean.] Cleaning that junk out from under the air filter chamber did not reset the p1135 Check Engine condition.

Q1) Should i go someplace and have the computer reset to see if the Check Engine light comes back on? I'm wondering if the junk from under the air filter caused the error (but i doubt i'll get off that lucky).


After getting back home a couple of days later (and some 150 miles later), I went to one of my regular garages and the PDF they had on the 2001 Camry P1135 error said something about a sensor Heater and something about a return circuit. I imagine the heating element is inside the sensor itself. They said it could be an electrical issue or an O2 sensor or even something else. They did not say which one might be the problem but said they had better computer diagnostics to narrow it down (sadly, they were booked full). This guy did warn that a rich fuel mix could damage or ruin my catalytic converter or maybe an O2 sensor (another mechanic elsewhere also said this could happen). As it is near the end of the month they are swamped with people needing Inspection. That's the case with every garage i tried here. I need to go out of town this weekend and am frustrated because i can't seem to get the issue addressed until next Tuesday at the earliest. Which is too late.

Q2) In a worst case scenario (overly rich fuel mix?) how far can i go before causing damage to the catalytic converter or other parts? If i drive from garage to garages am i asking for trouble? I don't want to screw up my car.


I have no idea if this is connected to the p1135 error code, but: Over the previous 2-3 weeks it seemed as if my hood area was hotter than it should be, complete with that "driving in 90 degree weather" smell that engines can make. This is even with our weather being much cooler than is typical for this time of year. 70 degrees is warm enough for this to smell happen. I did notice a bit of this in late winter come to think of it. I also noticed that the in-dash thermometer seems to report that it's hotter than it really it outside. I think i saw a 9 degree difference once. That's quite a bit! My cooling system looks OK and here's plenty of coolant. Should i drain the coolant and replace it?

Inside the car, even with the vents turned off, some air still comes in- possibly more than i recall from when i got it originally. The problem is that the air coming in seems warmer than it should be. If it's ~72 degrees outside, it starts to get a too hot inside. I can turn on the fan and select the bluest setting (which i assume means air is taken directly from the outside) and still that air is unreasonably warm. That leaves me the option of driving with windows down or the AC on- neither of which helps my terrible MPG situation. I lost my job and gas prices are climbing. :-( In the winter, the car seems colder than it used to be- that is, the heater doesn't put out air that seems as hot.

I also wonder if the p1135 error is related to a problem i've have for the past 20 months or so. Starting around Sept. 2007 there was a HUGE drop in fuel efficiency. I had one of those lucky wunder Camrys that seemed to get over 36 MPG highway, and seemed to get over 28 in the city. Then i suddenly started getting as little as 13 MPG city (winter) and 15-17MPG in the summer, and 17-23 MPG highway. At 13MPG i may as well drive a hummer! My driving habits have not changed- i always take off gradually and adjust my speed when i see a red light in the distance so as to avoid having as many stop/starts. And yet i was getting 13MPG! After a few seafoam/lucas treatments, at the right temperature, on a level highway, at exactly 55MPH, on cruise control, i can just about get back to about 30-32 MPG (i have no way to know for sure of the seafoam/lucas is what caused this partial correction). I used to be able to easily do 65MPH and get this many MPG. So i'm still far under what's normal for this 2001 Camry. And city fuel economy (or hilly driving) still exacts an abnormal efficiency penalty not seen until Sept. 2007. Its fuel economy seems to vascilate in ways it never did prior to Sept. 2007.

I tried the obvious corrections: proper tire pressure, seafoam, lucas, new spark plugs (my fuel economy seemingly got worse after the new plugs) . The timing belt was was last addressed at 82K miles (10K miles before i bought the car). I had a Transmission Flush done at about 112K miles when i found out the previous owner *never* had the transmission fluid changed. None of this seems to have put things back to normal.

Frick & Frack the Tapper Brothers on NPR once mentioned in passing that a bad thermostat can affect fuel economy so i'm wondering if perhaps one or more of these issues are connected.