lillexrx

Hi Everyone,

My 99 RX 300 (143k miles) has been having multiple issues lately. Have replaced 5 of the coil packs (some going out more than once).

I now have the following codes: P0125, P1133 and P1135 coming up. The Toyota dealership says I need an O2 Sensor, is this correct with the codes above??

Also, could some of these codes be from my multiple coil ignition misfires? Should I unplug the battery for 30 minutes and then go to Autozone to see if they show again?

Thanks for any replies!!

JAB

I am the original owner of a 1999 RX300 with 175K. I don't believe that I have ever replaced a coil pack, so I am stunned that you apparently have reason to believe that all of yours have failed. Regarding the codes, I suggest that you ignore the P125 for the present; reset the CEL; drive for a while and then pull the codes even if the CEL is not on; it will reveal the 'pending' codes that haven't yet triggered the light. I predict that if any are pending it will be the 1133/1135, which should tell you that its the Bank 1 a/f sensor that most likely needs to be replaced. Of course, if after reset the CEL light comes on before you can look for pending codes, I still predict that the Bank 1 sensor will be the culprit.

lillexrx

Hi JAB,

Thanks for the reply. Is the Bank 1 a/f sensor the same as the 02 Sensor? The Toyota dealership has ordered one for my car to put in on Monday, want to make sure I need that particular one!

JAB

You need to be ABSOLUTELY certain that the part that is being installed replaces one that is defective and addresses the diagnosis that has been made. Terminology is key here; the air/fuel ratio sensors (there are 2) are mounted on the exhaust manifolds (Bank 1 is closest to the firewall; Bank 2 is closest to the radiator); the O2 sensor is on the exhaust pipe just behind the catalytic converter. Some people continue to refer to the a/f sensors as O2 sensors which is not correct.

lillexrx

Hi JAB,

Thanks! The guy at the Toyota dealership called it the "02 Sensor" but the codes on the paper they gave me state the following:

Found codes P0125 Insufficient Collant Temperature
For Close Loop Fuel Control
P1133 A/F Sensor Circuit Response Malfunction Bank 1
Sensor 1
P1135 A/F Sensor Heater Circuit Malfunction Bank 1
Sensor 1

Help please...

JAB

Appears most likely that you will need to replace the a/f sensor on the exhaust manifold next to the firewall. However, if I were you I would spend the $35 for a code reader at Costco; clear the codes, and see what if anything reappears. But in my experience the P0125 is a function of a malfunction of one of the a/f sensors and does not, by itself, point to a part that needs to be replaced.

lillexrx

Thanks JAB! I read somewhere that I can unplug the battery for 30 minutes and then have do the code reader. The dealership told me that if I don't replace the 02 Sensor that it can damage my catalytic converter... Wish I could wait for a few months to replace this stuff...

lillexrx

I just remembered that I replaced the 02 sensor about 2 years ago, don't know how long they're supposed to last...

JAB

With a code reader you can reset the codes and don't need to disconnect your battery.

lillexrx

Cheers, JAB!

code58

When you say you replaced the 02 sensor 2 years ago, do you mean the B1S1 (at the back of the engine by the firewall)? Which is actually an A/F ratio sensor, or the actual 02 sensor after the catalytic convertor under the drivers seat? Either 1 should definitely last longer than 2 years. Often 100k mi and sometimes a lot longer. Might be a good idea to change them at 100k mi but may not set CEL for a lot longer.

lillexrx

Hi Code58,

I had it replaced at another Toyota dealership and they called it an 02 Sensor, they said that if I didn't replace it the car could stall, bad gas mileage, etc. And again, this other Toyota dealership is calling it an 02 Sensor... It's rather confusing to me.

When I took it in the last two times, it was for Coil Pack Issues (I've had 5 in the past year) and it was throwing out "Multiple Misfire Detected" Codes - then they told me that I had a bad 02 Sensor and that the CEL light would stay on until I fixed it.

The printout says P1133 A/F Sensor Circuit Response Malfunction Bank 1 - Sensor 1, and P1135 A/F Sensor Heater Circuit Malfunction Bank 1 - Sensor 1... I'm so confused... I don't want to replace something that doesn't need replacing, especially right now...

code58

Yes it is very confusing when even the dealers call the sensors by the wrong names. As you can see, at least the computer knew the correct term for it. It is a little suspicious to me to get both of those codes at the same time. I'm sure both functions of the sensor can go bad at the same time, but they are 2 entirely different issues in the same sensor.