cralpacas

99 lexus rx300 4wd, 87,000+ miles
Have ongoing problem with cel, since December. have recently replaced B2 S1 sensor, Mass air sensor, both the mechanic and I have checked for vacuum leaks(found one at rear of air cleaner). The code reader (Snap on) reads code 125 and 1153. If cleared engine will set parked for hours without triping the cel. Once driving can only go between one and two miles before cel comes on.
Does anyone have an idea as to which direction to go from this point.

cralpacas

lucky me I got to replace another O2 sensor (after all the old one was 90 days old). Anyway there is still a 125 code to address, anyone have any ideas? clues?

Lil4X

Don't take a lack of response here as disinterest - I imagine most folks are as stumped as I am . . .

I'm not sure what it is, but I burned out an O2 sensor on my RX 300 at about 45K - causing a number of problems with the OBD and cel very similar to what you describe. Maybe a cascade effect. Once you get #2 replaced, maybe the 125 problem will become more clear.

mikey00

My guess would be that you had a CEL, took at look at the code and started changing sensors. When that didn't solve the problem you found the hose behind the air box off and replaced it. If you found the hose before changing the sensors, it would have solved the problem. But now you introduced a new problem when changing the sensors. My first question is are they aftermarket? Did I get the sequence of events right? Or am I way off base.

rxdriver

It's hard to say without the RX service manual.

Guessing, based on generic DTC code information on the 'net, and assuming these are powertrain (P) codes:

P0125: Insufficient Coolant Temp for Closed Loop Fuel Control
I've got a manual for a 2000 Toyota Tacoma that tells you this is either an O2 sensor problem, an airflow problem, or a fuel flow problem.(Obviously, other things would need checking to narrow it down.)

P1153: Bank 2 Fuel Control Shifted Lean
The computer thinks there is too much air in the fuel mix. That doesn't help narrow down the above... that's just confirming there is either an air problem or a fuel problem.

Sorry I can't be more specific.

BurnishedGoldRX

Since both codes are for the A/F Ratio Sensor(s), did you check to make sure the harnesses didn't get damaged and that everything got reconnected? DTC P0125 won't show up until after the engine has warmed up and certain driving conditions have occured for 1.5 minutes.

cralpacas

All sensors replaced including the one replaced under warranty by lexus at about 10k- are suposed to be OEM. The 1153 code has cleared leaving the125 to deal with. I wasn"t very clear in my origional post in describing the vacuum leak it was a loose clamp at the air filter box. when the clamp was repositioned the cel would stay off for about 2 miles (instead of 1.5 ). fuel pressure at the front rail is in spec though I don' think the mechanic tested it under load or speed( have asked him to do so).

Lil4X after looking through the archives and not finding anything close to this, I figured you folks were thinking it through. You've all given me some ideas that i'll share with my mechanic (thou not a trained toyota/lexus mechanic he is very good[ and since he didn't fix it the first time it's on his dime this time] ). hope to have something positive by close of day will let you know the final outcome.

cralpacas

picked up rx this afternoon, have put 30 or so miles on it and the light is still off. The B1 sensor that was replaced in December burned out the heater element causing the 125 code. Thanks to all for your suggestions. Now all I have to do is get by the cost of two o2 sensors. As i said the mechanic ate the price of the third along with many hours of diagnostic time.