zxrmatt

Hi All! I wanted to post my solution here to the P2196 code followed by p0171 and p0174. I received these codes after replacing both of my A/F sensors (B1S1 & B2S1). I decided to purchase the replacement parts from RockAuto after doing hours of research to understand that this 2002 ES300 has 2 O2 sensors before the catalytic converter (A/F sensors specifically) and 2 O2 sensors after the cat. The latter pair I refer to as just O2 sensors. The former I will refer to as A/F ratio sensors or A/F sensors. I did purchase an O2 sensor socket to make the replacement job easier on myself. The other preparation I did to ease the job is spraying PB blaster onto both A/F sensors about 30mins before attempting to remove. I believe B2S1 (A/F sensor closest to the firewall) had very tight quarters to work with. I took the advice from a video describing how to easily remove this sensor by removing the passenger front wheel. This really helped me a lot in terms of juggling the new A/F sensor into place and luckily threading it in the correct way.

So, the engine performed perfectly for one night. This one night included 3 on/off cycles. When the car was turned on the next day (4th on cycle) it started exhibiting different symptoms and the CEL came back on. 1st issue it presented was a severe idle dip when accelerating from a complete stop or when coasting down the road with the gas pedal not depressed (foot off the gas pedal) and then resuming use of the gas pedal to maintain speed (foot depressing the gas pedal). 2nd issue presented was WOT applications (gas pedal depressed all the way to the floorboard) did not allow the car to down shift automatically to pass slower traffic in a designated safe passing area of the road. To me, this felt like the clutch or gear that the car wanted to use would not engage. The engine RPMs would go up, as if it were going to comply with the WOT request, but then the gear or clutch never engaged, Strangely enough, only 1/4, 1/3, 1/2 and 3/4 throttle positions were usable. Also, gas mileage took a nose dive into truck/suv territory.

Okay, so I go to my local AP store and ask for assistance with pulling the codes. 1st one to show is P2196 with P2197 (I think that was it) pending. Those 2 were followed by P0171 and P0174.
P2196 and P2197 = A/F Sensor stuck rick. B1S1 and B2S1 respectively.
P0171 and P0174 = B1 and B2 running lean respectively.

My initial thought process to remedy this was to fix the lean conidition 1st in order to fix the rich symptom. I hunted for hours for about a week looking for vacuum leaks. None were found. Did more online researching and found that you need to solve/remedy the codes in order from 1st to last. So, instead of trying to solve the lean condition 1st, I needed to solve the lean condition last if it still existed.

One of the possibilities could be that the A/F sensors that I installed were faulty. I had a very difficult time believing that was the case. Next to check was the MAF sensor. Okay. My easy way of checking th MAF sensor is to disconnect it, Start the car and go for a quick test drive. With the MAF sensor disconnected, the engine didn't go above 3k RPMs. For anyone who has any experience with these v6 engines, it doesn't really wake up until about 4k or 4.5k RPMs. Based off of this, I knew it was the MAF sensor. I came across the DIY- MAF sensor cleaning thread in the RX 1st Gen sub-forum. It gave detailed instructions on what was needed to complete the job. If this didn't work then I needed to do more t/sing before throwing larger amounts of money (parts replacement) at it.

Cleaning the MAF sensor in our 2002 ES300 is completely safe to do. It does not have the Karmen Vortex MAF sensor as some Toyota and Subaru vehicles do. The MAF sensor type is a Hot Wire (I believe that's what it is referred to as). L-type MAF Sensors can also be cleaned. After following the steps in the MAF DIY thread from the RX 1st gen forums, ALL 3 codes were cleared and never returned. It's been about a little over a month. The only difference I see now is that the engine idles lower (500 RPMS) when warm/at normal operating temperature.

I do need to stress that cleaning the MAF while experiencing similar drivability issues won't be the solution to your problems. Though, if the circumstances surrounding your issue is similar to what I have described here, then it's worth a shot doing to save some dough and not have to replace the MAF sensor.