RayN

99 rx300 awd, 96K miles. Car seems running fine but throwing a cel P0125 and P1155, any idea what the code means?

RayN

P0125 Insufficient coolant temperature for close loop fuel control
P1155 Air/fuel ratio sensor heater (bank 1 sensor 1)

I think P0125 is related to P1155.

P0125 check coolant level, thermostat stuck, faulty coolant temperature sensor

Lexmex

You are correct on the codes. Did they still pop up later after you cleared them?

RayN

I cleared the code and same code pops out. You think I need the bank 1 sensor?

I cleaned the MAF and IACV already and still same code pops out.

Lexmex

The only way to really check this is with an advanced OBDII scanner that can read the readings off of both A/F sensors.

Lexmex

Actually P1155 is bank 2 sensor 1.

RayN

bank 2 sensor 1 is the A/F sensor by the firewall right?

Lexmex

That should be the one in front by the radiator.

RayN

I read the MIL again before replacing the air fuel ratio sensor, the code are P0125, P1155, P1153, P1155. So I bought the air fuel ratio sensor at Toyota dealer and replace the old one, reset the MIL. About, 50 miles now, check engine light didn't show up.

Meetya

I just made this post:
https://www.clublexus.com/forums/sho...d.php?t=282920

roseyyz

Hello RX300 people! Does anyone knows what this constant P0125 and P1155 combo on CEL means? I've changed EVERY sensor there is (A/F DENSO), even changed thermostat with timing belt, -all parts genuine Toyota- so the P1155 really annoys me,not to mention the 0125.. geez... Also, every valve has been cleaned, properly adjust, maintained or whatever there is and STILL i get these codes.

Something I notice is that when in a red light, the RPM get a little bit low and the vehicle seems to be loosing power so I have to put it on N and accelerate a bit... ??????

Might be something related to a throttle problem? Or these are totally different problems and are not related? I would appreciate any feedback, I am totally blocked but I sure want to fix this! Thanks for reading!

roseyyz

Great! Definitely my mechanic has some homework!

JAB

Did you change all three sensors (2 upstream, 1 downstream)? In my experience, if you change the correct upstream sensor (either the one by the radiator, or by the firewall) the P0125 will go away.

roseyyz

I believe I did, anyway will double check with mechanic, thanks a lot!