Jacob0015

Hello everyone,
I have a 1999 GS 300 and my check engine light recently came on. I ran an OBD II sensor on it and recieved the code P0155 which is for an "oxygen sensor heater circuit on bank 2 sensor 1". I've looked up diagrams and checked my manual for this problem and I've had a hard time understanding them. Can anyone give me some help for where this sensor is located (pictures preferred) and what part(s) I will need? Thanks in advance!

iToaster

Bank 2 is the rear 3 cylinders, sensor 1 is before the catalytic converter. This is one of the codes I had when I bought my GS, I replaced the sensor and it fixed the problem. The sensor is right by the firewall and will be challenging to remove without removing the header, but it is possible.

2GSKaizen

iTrader: (1)

Yep agreed. It is a huge PITA to get to, but I was able to get mine out with the header still attached using a pretty large 7/8 inch Snap On wrench. Hit this with some WD-40 for 2 days before you plan to take it out. They will be very difficult to break loose if you don't.

j.tom

iTrader: (1)

Toughest one to remove on this car.

Jacob0015

Okay thank you for the diagram and the replies! I've been looking around online and it appears that this really is a difficult task, though I'll attempt it. I've found the OEM part, which is a Denso oxygen sensor numbered 234-4630 (in case anyone has the same problem and needs the part number). I plan to get to it some time next week, so if there are any precautions I should take then please let me know, thanks!

Jacob0015

Oh and one more thing, if I'm facing the car from the front, would the oxygen sensor on bank 2 be on the left hand side of the engine?

2GSKaizen

iTrader: (1)

They will both be on the left side of the engine if you are looking under the hood since it's an inline 6. Bank 2 will be the rear sensor. It is in very close proximity to the firewall. Find the exhaust manifold, follow the 3 runners that come from the rear 3 cylinders, sensor mounts right above the catalytic converter.

Blanco

iTrader: (8)

PB Blaster will work much better than WD40. If it needs any penetrating oil at all.

tiger4life

iTrader: (16)

I got it off without removing the header. I don't remember it be that difficult. Space is tight,but I wasn't cursing the car. It's a California car though so I don't know if that helped.

Jacob0015

Okay thanks guys for the suggestions, I'm going to order the OEM part soon and I'll keep you guys updated.

Jacob0015

The part came in today. I've located where it's supposed to go and it's going to be tight but I'll take my time. Gonna attempt it after work and see what happens. I'll include some pics as well.

Lexicious

Rockauto.com best cheapest parts website for oem equipment

Jacob0015

Hello again everyone,
Sorry I haven't updated in a while, I've been busy but I finally got around to replace this sensor and it was a success. The check engine light is gone and I'm now getting better fuel economy. Here's what you need to do:1. Parts - Get the correct sensor (234-4630 is the part number for Bank 2 Sensor 1), some anti-seize, and something to loosen up the hoses (I got something that penetrated the hose and softened it up, beware though because this makes it easy to take off the hose but hard to put on the clamp since the hose expands a little).
2. Tools - I didn't use an O2 socket because there just wasn't enough room so I settled for a smaller wrench. Also get some good vice-grips because the hose clamps can be a real PITA to get off because the bite is pretty wide and the space is confined.
3. Procedure - Remove the blow back return tube (little rubber tube that connects to the firewall side of your air intake).
4. Remove the bottom heater hose, which is the twisty thick hose that attaches to your firewall on the passenger side (there should be two but I only removed the one that's more left, also the clamp in this one is very difficult to remove and put back on, take your time). I sprayed on my rubber penetrating compund that I got from Autozone (forgot the name of it, ask the Autozone guy and explain that you need something to loosen up tight corroded rubber hoses and he'll get it for you, has something to do with belts or what not) and used a wrench to wiggle/loosen the hose and then pull it out.
5. Now that you've got some space, you'll see the O2 sensor on the back 4,5,6 pipes before the cat converter. First unplug the sensor from its electrical attachment. (follow the wire up and you'll find it) There is an alligator clamp holding the wire so make note of that. Then, using your wrench, (it's a big size on the sensor so you need a small wrench that opens wide) unscrew the old O2 sensor (it may be on tight, take your time) and remove it.
6. Put some anti-seize on the threading for your new O2 sensor (don't get it on the tip of it) and screw in the new one with your hand (be careful, the tips of O2 sensor are sensitive and you don't want to bang it around)
7. Tighten it with the wrench. Once its on tight plug in the wire to where you unplugged the old one. Reattach the alligator clamp to hold the wire.
8. Reattach the bottom heater hose (take your time and use the right tools, those hose clamps suck!).
9. Reattach the blow back return tube (a lot easier).
10. Congratulations, you're done.
Remember space is VERY limited on this one so take your time and try not to get frustrated and rush things. Take breaks in between if you need to but don't try to froce things in or tear things off. Use the right tools for the job and it will make it a lot easi... less difficult than it already is. I'll try to include some pics of things but can't right now because I'm at work (LOL). I also changed out the spark plugs and wires so I'll see if I can make a thread on that. Anyways hope this helps guys and thanks for the pics and recommendations prior.