Need To Replace Sensors

[soko420]

I did a search, but didn't find what I was looking for. I have a 1999 RX300 that's getting at most 10mpg, rough idle, and jerky shifting. I checked my codes and got these in this order P0171 (system too lean), P0125 (insufficient coolant temperature for closed loop fuel control), and P1155 (air/fuel sensor heater circuit).

I cleaned the MAF already and the problem is still there. I think I might need to replace the MAF, but what other sensor(s) do I need to replace?

Can anyone tell me the right sensor(s) to replace, where to buy them cheap, and a location of a FAQ/Guide to install?

Thank you.

[PK_3]

In broad terms It’s sort of self explanatory . This is only an educated interpetation;

P1155: Some Oxygen sensors (especially widebands) need to be artificially heated. If it not, it will think it cold and run the car rich thus giving crummy mileage.

P0171 say not enough coolant to create heat. Same deal, it not reading the heat required to heat the O2 sensor enough to make the car right. Same deal, to rich, ergo bad mileage.

P0171 (system too lean) makes no sense to me because the other code and your mileage point to a car running rich. It may just be a code thrown out because other things are screwy and the computer doesn’t know how to take it. Or, maybe one bank is running so rich, the other compensating by leaning way out.

Anyway, this is just horse sense but I’d say you have a problem with an o'2 sensor or wiring to it, or your low on coolant is low (unlikely) Both the same symptom to the computer.

Hope this broad analysis and helps you.

Regards, PK

[soko420]

I was on another forum and they helped me. I'm replacing the A/F sensor in the manifold radiator side, thanks for your help too.