Shaun ES300

Had same problem with a 2001 ES300. My spare key wouldn't work either. Then I noticed the red light on my spare keyfob would not flash when I pressed buttons. A sure sign the battery was dead. I went to Radio Shack, purchased a battery (CR1616 3Volt Energizer) and put it in the spare key. Now the keyless remote works like a champ. Not to overstate the obvious - but when replacing the battery, probably important to put it in the correct way ("+" side up). Only other comment I have is to confirm your red LED is flashing bright when pressing a control button. If the light is dull or not glowing - battery should fix the problem. Shaun

Sure taking this issue slow. I've checked my gas mileage and getting 22mpg in city so I guess that's reasonable. Thanks to this board for the advice about Advance Auto Parts. They ran a OBD-II check for me this afternoon and I only had a P1135 error code. Nothing else. If memory serves, that is the heater element for the B1S1 sensor (the really hard to reach one). If I can get my hands on the quick disconnect, I'll do a resistance check on it before taking further action. At least the OBD-II read from AAP checks with my earlier puzzel as to why B2S1 heater circuit measured as good functioning (grammar??)

Checked fuse (25A) and it is good. Lifted the car and took a look at B1S1. Holy crap! I think I could remove the sensor but reaching up to disconnect the plug in connector looks rather daunting. Engine was too hot to reach up and try. Other priorities this weekend so I'll have to put off until later.

Thanks George. Appreciate the info on the "ohm-age". I know where fuse box is but haven't a clue which fuse works this circuit. I'll try my trusty owners manual to see if it will help. Yes, the CEL came on last weekend and since I needed some service (fluids, rotate tires, etc) I asked Firestone to to a diagnostic. I agree, two AF sensors going out seems odd. (I do have 90Kmi, tho). Fortunately, I have a parking lift so I can get under the car to look at the other AF sensor and check it's resistance. So far, no poor gas mileage so I think my cat is safe for a little while.

Thought I read somewhere that resistance for the 2000/2001 AF heater circuit was lower ohms. I might have run across a pdf showing the resistance check but can't find it tonight. Thanks for the advice.

I've done a lot of checking and for a direct fitment AF sensor, $140 each is about as good as I could find. I want to check a fuse as you noted but don't know which one for the ES300. Can you provide specific location? Thanks

My first post so forgive if I goof up. I have a 2001 ES300. Have CEL and Trac Off lights on. Firestone OBDII diag. says P1155 and P1135 and they concluded 2 AF sensors required to fix. ($670 total). Looking over this site, I've learned a little bit. I've diconnected B2S1 and measured resistance at AMB temp. Measures about 1.2 ohms. I see a pdf for 1997 ES300 stating higher resistance but think my '01 might indeed be correct at the lower resistance. The CEL's were for heater circuit malfunction so I expected to see O.C. if bad. Before go and buy 2 new sensors (I do have the correct Denso part located) can anyone advise to other trouble shooting before I drop $300 on the AF sensors? Thanks, Shaun