Greetings Club Lexus!

I drive a 2000 RX300 and a couple of days ago I got the great "Check engine" light on my car with the Trac off light flashing on after about 10 minutes of the car running. Took it to the dealership and it gave them codes P0125 and P1130, For Insufficient Coolant temp and A/F Sensor for bank 1 sensor 1. they said replacement of my T-Stat and replacement of the Sensor would clear the two lights. Biggest thing is, if I go with these guys, its a whooping 675.00 USD!

Question is, I don't forsee the T-Stat being hard, but the Sensor? I have looked online for some info but haven't seen anything that might help me. Should I suck it up and just pay the 675.00? or is it something easy? The parts seem pretty cheap with the sensor being the most expensive at about 47~100 USD.

I know thats kinda vague but any information would be greatly appreciated!

 

SlickVic- Not sure where you got the $47-$100. price for the A/F ratio sensor but that's not right. The Toyota/ Lexus (Denso) # for that sensor is 89467-48011 and the list is probably $200.- $245. (whatever the particular dealer wants to charge. Don't ever think that when a dealer gives you a parts price that's what it's gonna be everywhere, they can and do charge whatever they want to). You can buy the sensor online in Denso with the Toyota # for as cheap as $150. from a Lexus dealer or you MIGHT find it a little cheaper with the Denso # (234-9009) Same sensor. I WOULD NOT recommend using anything other than Denso. Trust me! I see you're from Ill., rust country. That is the rear sensor (by the firewall) It is the harder 1 to change but many have done it (and lived- LOL) Having said all of that, I would change the T-stat 1st and clear the light and see if it actually comes back. Sometimes you have multiple CEL's and dealing with 1 will deal with the others, because they were only "triggered" by the 1st. and weren't actually a fault. Cardinal rule! Codes are not the Gospel! It takes some knowledge and digging to go along with them. Don't throw parts at the car, many do and only end up poorer for it. Make SURE your car needs a part before you put 1 on or the poor house may be your future home!

IF you change the sensor, make sure and soak it good a couple of times with a "rust-buster" before you attempt to remove it.

 

I doubt that you need a new t-stat. The P0125 code often shows up as a companion code to P1130 and does not necessarily mean anything is wrong with your coolant temp control. This happened in my case. I suggest you fix the A/F sensor first.

A/F sensor failure is common. T-stat failure is unusal.

 

One other thing. Sometimes, the coolant is old or contaminated. With that combination of an A/F sensor code and the P0125, sometimes just cleaning out the coolant can help, otherwise as artbuc says the A/F sensor would be the primary issue.

 

me and a friend are trying to locate the senor... I have taken a few pics, maybe you can point me in the right direction? Another friend of mines is a mechanic, but he is deployed (go figure ) so I am trying to complete this myself. (with help of course)



any thoughts?

I think I am going to get the lexus maintenance manual, cause I am not even sure about the thermostat... I know that its usually right above the radiator in the big radiator hose...this is really it?



Cool, I will def change the coolant while I am down there, I just can't believe how much labor cost these days. I am just over my warrenty and of course, everything happens now. Looks like I will change the sensor and go from there!

 

Coolant error code is mostly likely an code you can clear if A/F sensor is replaced. As Lexmex and artbuc said, I would also focus on A/F sensor.

 

P1130 is Bank 1 Sensor 1 and that's a PITA because it is behind the engine.

 

T-Stat would 2x PITA. No need to replace unless one wants an performance T-stat that opens up at lower temp.
Thanks for the recommendation on TOM T-stat, it is doing well for me.

 

T-stat is actually on the driver's side of the engine block. You'll have to remove your airbox and drain the coolant, but it is behind this metal piece circled in white.

Note the a/f sensor at left, as that is the same one you show in one of your photos above.

 

LOL. That was a major PITA to get out.

 

Yeah I don't know what I was looking at, 210~240 is the floating prices around these parts.

Everyone thanks a lot, I just got under the hood to check these places out O.O its gonna be a blast getting the A/F out

You guys rock!

 

Art- Do you know what a Scan-Gauge II is? I had 1 of the original SG's and now have a SGII. I loved the original (except truly ugly) and love the II much more. I have it set up to mount in 2 different positions in the truck and also in my wife's car. It will easily deal with quite a few of these things without any question. I just didn't want to see him either pay a ton of money to have it done or the money for a sensor, if he didn't need it. I'm going this evening to try and help a guy who have thrown a lot of money (in parts) and time into fixing a CEL and things are worse now than when he started. The parts stores love those type (keeps 'em in business)

 

I don't have an OBDII reader let alone a SGII. As I understand it (and I could be wrong for sure) P0125 has to do with the A/F sensor performance after the car is warmed up to normal operating temperature. The reference to "coolant temperature" is really a misnomer. Now, if the ECM thinks the car is at normal temp and it isn't, then I suppose you could throw P0125 without having a bad A/F sensor. However, I think that would point to the coolant temp sensor not the thermostat. I think having P0125 and P1130 at the same time means it is 99.99% an A/F sensor malfunction. Even though a t-stat would be cheaper than an A/F sensor, it would be a waste of time and $$ to replace it based only on P0125, IMHO.

 

Correct, and the manual indicates as much with the P0125 and the A/F sensor.

I am hoping to get soon some advanced software for my laptop, very soon, (but still analyzing options), perhaps something like Palmer Performance or Digimoto so I can do some more advanced OBDII data reading than just a basic OBDII reader so I can analyze better when I get codes and see what is going on underneath.

 

Which would make sense, I get the P0125 after the car is warmed up for 10~15 mins.