BrandonLee

Just bought the car and everything was fine until this weeks sudden onset of cold weather here in MN

2001 with 142k. Check engine and VSC came on. I pulled the battery and reset and the codes disappeared for a few days. They came back on today and I Autozoned them.

I got codes:

P1150
C1246
C1223

Under the P1150 code, the reader read:

Air/Fuel ratio sensor circuit range/performance manfunction (bank 2 sensor 1)

From my experience with Toyota cars and the bad gas mileage I'm getting, I am guessing it is actually the sensor and none of the other possible things that the OBD lists (vacuum leak, fuel pump, etc) If so, I need part Denso 234-9009, correct?



Next is the C1246 and C1223 codes. (Master Cylinder Pressure Sensor MCPS)

First let me say that I haven't really worked on brake systems before, just the basics like swapping out rotors/pads. So I am really lost on this.

I searched around the forum but couldn't find much, specifically for the RX300. Where do I start on this? Currently, my car brakes fine and there is no notice of brake fluid leaks or performance issues. I thought I felt a very slight vibration when braking, but I always thought it was a slightly warped rotor. Could this be a symptom?

Also, I have been researching Lexus/Toyota forums. I notice a lot of people saying getting BOTH the O2/AF sensor code and master cylinder code at the same time. Is this a weird coincidence? Do you think the AF sensor, which I am for sure is bad, is causing a code to trip up the other things? Some people have also mentioned only replacing the O2/AF, doing a reset, and never having a light back on. Also, people have mentioned the ABS actuator system could be the issue rather than the MCPS. And I don't even wanna wrap my novice mechanic head around replacing that.

Any advice would be appreciated. Thanks all.