hksimpson

So the check engine light on our 1999 RX300 with less than 50K miles came on and the scanner shows P0125, P1135, and P0171.

This happended on a trip so we drove the 300-miles home and I reset the light by pulling the battery and it came back on after about 10-miles. Car was running the same, but now I have a rough idle.

Solutions on each one of these codes seems to be all over the place. Best place to start? I am hoping I just need an oxygen sensor and these are the result of that.


P0125: "Insufficient coolant temperaturel"
P1135 :"Fuel air metering"
P0171: "System too lean (Bank 1)"

Tammy

Search for cleaning or replacing the MAF sensor. Is your engine air cleaner need to be replaced?

http://www.lexusownersclub.co.uk/kno...v2&id=152&c=11
https://www.clublexus.com/forums/sho...ighlight=p0171

Check for a MAF spray cleaner available in auto parts stores

hksimpson

I will clean the MAF and check the air filter today. If that fails it seems many relace the O2 secsor for bank1, sensor1 (firewall side on exhaust manifold before cat) as a second step.

Anyone got a picture of that location? There are lots of pictures in the forum but I could not tie them together.

Tammy

All wheel drive or front wheel drive?

hksimpson

Four wheel drive.

Tammy

Lay down a towel or something...

Crawl under the passenger front door, towards the rear of the engine. You'll see the propeller (drive) shaft to the rear differential. At its front, the catalytic converter for bank 1. Just above the converter, bolted into the right side of the exhaust pipe is the sensor 1.

Lexmex

Mine is an AWD and the picture I posted in this thread is correct.

https://www.clublexus.com/forums/sho...d.php?t=206027

Just follow the pipe going up from in front of the catalytic converter. I know it is a pain to get under there and look up and even fix this, but that is where it is. I do not have any precats so it makes it easier to show in that picture, but you may have a hard time looking around the precat to see the O2 sensor.

Tammy is right about checking out the MAF.

If the MAF gets too clogged or dirty it can cause an overheat (this happened to me once and then I cleaned my MAF for the first time a few years ago) and I then reset the CEL with the EFI fuse. The overheat actually caused the original paint on my engine cover to partially melt...one of the reasons it is painted silver today.

A faulty O2 sensor can also cause the above, but don´t go spending money until as Tammy mentioned to check the MAF sensor.

One thing I like to use in the coolant to help prevent such overheats (but it is not an absolute cure) is Redline WaterWetter, when I can get it from the U.S., or I use Nology NotHot, which is almost as good and readily available in Mexico City. One bottle of the WaterWetter or two bottles of the NotHot and that should help.

hksimpson

Thank you both for the time and advise. I will look at it later this weekend and I hope it is not the O2 sensor because it looks like a pain.

BTW, AutoZone loans the code readers for free if you pay a deposit. This means I can do the work and then check a code if the light comes on without having to go back. When I feel everything is fine, I take it back and get my money back.

hksimpson

I replaced the air filter and cleaned the MAF. I used CRC MAF cleaner for that task and it seems like a good product, but the MAF seemed clean to start with.

Drove for about 5-minutes and check engine light came back on!

Codes are 0125 Coolant Temp and 1133 Fuel Air Metering. I am going to drive it a little more and see if it throws more codes but I am not sure what the next step is.

Funny how the 1133 and 1135 seems to have the same description.

Edit: I think I am going to replace the bank 1 oxygen sensor (the one on the rear exhaust manifold before the catalytic converter) unless someone else has any other ideas.

Thanks

yourrx300

Hello experts,
I need your help.My AWD-RX300-Yr2000 with 105K miles just showed these CEL codes. P0125, )1135, P0171, P1130. Haynes manual mentions (on page 6-12) that there are only two O2 sensors for year 2000 model. One on front of the engine towards radiator and the other behind first mufler (just under driver's seat).

But this thread says there is one more
"Crawl under the passenger front door, towards the rear of the engine. You'll see the propeller (drive) shaft to the rear differential. At its front, the catalytic converter for bank 1. Just above the converter, bolted into the right side of the exhaust pipe is the sensor 1."

Anyway, what is the fix?
Which parts were replaced?
Do you have OEM part numbers?
Thanks in advance.
-myRx300

Lexmex

That other one is the O2 sensor, and throws a different code, usually a P0420.

What you need is the A/F sensor for Bank 1, Sensor 1, which is behind the engine block and shown here. I am not sure about the OEM part numbers offhand, but others might know. Stick to the Denso (OEM).

code58

Hi hksimpson- First thing- it is important to understand that you need the OBDll codes specific for LEXUS. The P1135 code from a non-Lexus specific MAY read different than a Lexus specific. If you have a Dvm you can test the heater in the A/F ratio sensor to make sure it is bad before you spend $150.-$210. for a new one. Using a Dvm set to ohms, test the resistance between terminals +B and HT. It calls for 0.8 to 1.4 ohms resistance. if no resistance (broken heater wire) or out of range- replace. Make CERTAIN you get A/F ratio sensor and not OXY. SENSOR. BIG difference! And as Lexmex said, stick with orig. eq. Denso. The codes 1133 & 1135 on a Lexus specific chart DO NOT read the same description. Good Luck!
The Part# for the A/F ratio sens.- 89467-48011

code58

Hi myRx300- First thing to do is try and find a Toyota manual (orig.eq.) and deep six the Haynes . I am not a big fan of Haynes- too generic and too much bad information. Read my post # 12 for some info. P1130 shows A/F sensor ratio circuit range/performance malfunction, bank1, sensor1. P0171 shows system to lean. Go to www.OBD-Codes.com a lot of good info there.
Listen to Lexmex- He will generally lead you in the right direction. Hope this helps. Y/T- Roger