Got a p0161 today. After reading through threads searched on this site for 4 hours, I know exactly what it is and what to do, etc. However, on one thread for a different platform, saw a reference to a fuse for o2 sensor heater circuit. Does the ls400 have a fuse for said circuit? My manual makes no reference to a fuse specifically for that, but does show that many fuses cover more than one sub system for the one fuse.. would anyone know if the o2 heater circuit is bundled under another fuse that is designated for something else? Also, is the same circuit for all 4 o2 sensors? I'd that were true, then I would have a code for all the sensor heating circuits at once, yes? Trying to rule out things scientifically before getting around to pulling up my carpet and all to replace the one sensor.

 

All 4 O2 sensor's heaters are getting +B 12V from the EFI #2 fuse.

 

 

You're code is for the bank 2 sensor2 heater. Bank 2 is on the passenger side of the car. If you look at the downstream sensor and look at the four wires going into the sensor, two of them will be the same color. Those two are your heater wires. If you pull the connector off and read back towards the sensor, you should read in the 2 to 10 ohm area. If you don't read anything, you have a bad sensor. If you get the correct reading, you probably have a wiring problem. I haven't played with my sensors yet and am not sure how hard it is to unplug those sensors(they could go up into the interior of the car and be hard to get to the connectors).

 

thanks for the tip. will check that out. i am tending to think that it could be the sensor, as it is very recent, and maybe plowing through that puddle recently caused water to get in the sensor and **** things up. but yeah, will test that first.

 

update: ok. it's been an eventful day. after not driving for four days, i finally got out to do some errands with car. car dies. stutters, weird loping idle, and over a dozen engine codes, along with a slow-blinking trac/off light, and a staying-on CEL. drove for a while this way. got home, researched all of the codes, some that don't even seem to exist to the OBD-II guys on the internet. all of this I finally traced to the efi-2 fuse in the engine bay, blown. Yamae pointed this out originally, telling me that my original single code was for the one oxygen sensor that had the issue, and, now, all this snowballed. I finally forced myself to look under the car. I don't have an under-shield. the wiring apparently caught on something, and totally ripped the head off the oxygen sensor. all the electrical connections were sticking out, and seemingly had been dragging on the ground for a while, from the erosion on the metal that was left of the head. the electrical connections banged together, and shorted out, going all the way back to the efi-2 fuse. so, i cut the dangling part off, and isolated the wiring. replaced the fuse. runs perfect. gee. this ONE fuse covers, apparently, all the oxygen sensor heating circuits, the MAF circuit, rear ABS solenoid/motor #1, EGR circuit, ambient air temperature sensor! I also got a whole bunch of additional codes with my obd-II app, many of which don't even exist, according to the Net. so. after performing that temporary disconnect fix, and replacing the blown fuse, and clearing my codes, I'm back to a single code that I started with. phew.

yeesh. now, the bank 2 sensor 2 oxygen sensor is completely disconnected, what does that mean as far as fuel consumption, lean/rich, what? no codes from the other 3 sensors, thankfully.

 

The downstream O2 sensor is only checking the efficiency of the catalytic converter and it does not affect the fuel to air ratio. Even with the open heater, it works several minutes after your engine is started. The heater only works while the sensor is not warmed up enough.

 

in this case, the sensor is completely disconnected, the oxygen sensor in question is null and void. the wiring, all 4 leads, completely detached. there is only a stub screwed into the exhaust line. if not replaced and reconnected, i can anticipate i will get a code related to catalytic efficiency or something like that, eventually.

do you suppose a sensor taken from a junkyard vehicle would be suitable, or should i put out money for a single brand new sensor for that location? given that the other 3 sensors are old, and particularly with the upstream ones, difficult to replace, i'm not flush enough in cash to replace the other three, if the one downstream being newer than the others might throw off readings taken by all 4 as a group.

 

I wouldn't use a used O2 sensor.

But if you don't want to purchase a new one quickly, there is a way to use a current O2 sensor cheating the ECU that the heater is OK. I don't recommend this trick but instead of a heater, a resistor or an incandescent bulb can be used to cheat the ECU. I haven't tried this for my car but requested by shop owners, I sometimes use this technique temporarily for other cars when a new O2 sensor is not quickly available. The ECU checks the resistance of the heater and when the resistance is bigger than the limit, it judges that the heater is not OK.

Regarding the resistance, it depends on cars. Sometimes 1000 ohms is enough but sometimes much smaller value like 27 ohms is needed. Be careful for the heat when you use smaller value resister! Bigger the resistance, lesser the heat!

 

as an electrician, I know about cheating the heater circuit. That's not the thing, though. This sensor is COMPLETELY broken. All 4 wires are broken off. Can't cheat the oxygen reading; the ecu looks for the current to be variable while in operation. No way around it; I HAVE to replace it.

 

I see.
I don't recommend this neither but there's still a way to cheat the ECU for the time being if you don't want to see the engine check light. Connecting the Bank 1 sensor's signal to the Bank 2's sensing line, the ECU can be cheated as if the bank 2's cat is working OK. You still need to cheat the heater circuit using a resistor though as I wrote at my previous post.

 

well, went for a new sensor, proper harness and everything. it was SO easy to change it out! the carpet pull-up, getting old sensor out and new sensor in. getting the old sensor out wasn't very difficult, I did it while the car was still hot (my thinking that expanded metal of the bung would be easier to free, than cold shrunk metal), used my jackstand to break it free and it screwed right out, and new one screwed right in, and made it as tight as i humanly could make it. i'm seeing the car idle better, and time will tell if mileage improves. at 51, DIY is something i have to really feel confident doing, when my back permits. but, the big ones, the starter, the timing belt and water pump, etc, i cannot do, as i only have street parking in the middle of the city. eh. still love my car, though.

 

Excellent job DL,I learned lot.Thank You.

 

glad it worked out. for us Californians whose cars don't see much climate change (or road salts) removing the sensor is easy.
for those in the Midwest/east coast may be a different story which is why they invented PB blaster!

 

Hi You guys have more experience than me but I have been chasing fault and changed both bank 1 and bank O2 sensors but I still get a o2 sensor heater circuit fault, can anyone help me identify
and find the sensor that turns on and off the o2 heaters? Oh this is on My wife's GS300 2002 straight 6, that she loves and wants to keep forever. cheers