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I've had the code P0057 coming up. I've changed the corresponding sensor (it was a gigantic PITA), and the code came back.
It says HO2S Heater Control Circuit Low (Bank 2 Sensor 2). With some reflexion, it seems like I've not taken this literally enough and thought the O2 sensor itself was bad, although the code is about a heater circuit. I thought it was an ambiguous term to refer to the O2 sensor, but I learned there is in fact a heating resistor in the sensor which makes it go faster to a temperature where it will read the correct value.
Because 1. the signal in Techstream looks like the one from the old sensor, so it may not even has been faulty to begin with, and 2. I've looked up further on this problem, and a website came up with the possibility that a fuse for the heater circuit could be blown. I looked up in the manual and I didn't see a fuse dedicated to O2 sensors heaters.
One of the possibilities is the resistor in the sensor went out, but I changed the sensor, so I think it has to do either with the wiring, the ECU or a fuse.
I'm a bit skeptical regarding the two first options though, so I would like to begin with the fuse. Is there such a fuse in the GS? I may eventually take it to Lexus for further diagnosis.
Thank you
Last edited by PauloFR; 01-20-21 at 08:35 PM.
Reason: Problem solved
Another member had the same issue with his 2006, I forgot his sc name but he was from Canada aswell. Try searching old archive for his posts on 2006 o2 sensor. Maybe it was water or ground issue, I am not 100% sure but I remember it was bothering him for the longest and he did eventually figure it out.
I searched before posting, but I only found 5 threads from people who just had the code appear and don't know yet what to do, not from someone troubleshooting the heater circuit.
It could indeed be useful if you remember which one it is, he may have formulated his post and title differently from what came to my mind to search.
I landed on this thread and I think this is the one you were talking about
Originally Posted by Jumbojoe55
'07 ES350, 70,300miles
I replaced bank 2 sensor 2 with a Denso part, will the check engine light turn off by itself or do I need to clear the codes myself?
Which fuses do I check as part of the troubleshooting for P0057?
But I checked many fuses related to the EFI (5, 12, 55, 70, 79) and all were good. The solution I found at the end of the tread was, well, replacing the sensor.
I'm at the same time defeated and afraid, because as per the documents, one of the possible causes is the ECM which costs an arm and a leg to replace.
I landed on this thread and I think this is the one you were talking about
But I checked many fuses related to the EFI (5, 12, 55, 70, 79) and all were good. The solution I found at the end of the tread was, well, replacing the sensor.
I'm at the same time defeated and afraid, because as per the documents, one of the possible causes is the ECM which costs an arm and a leg to replace.
Not an under the bonnet fuse link is it, or a possibility of banks reversed, as in changed the wrong sensor?
I checked fuses in the 2 boxes under the hood as well as the passenger footwell. I'm also convinced I replaced the right sensor because I checked many times not to replace the wrong one. But at this point I don't even think it was bad in the first place but something messed up on its own in the heating circuit somewhere else in the car.
I've come across a website where you can ask mechanics. It was paid but the trial was just $5 so I went with it. A Lexus master tech gave me the AllData diagrams and repair procedures, very complete and helpful, but they just confirm it is either the ECU or the harness. And obviously neither of the two satisfy me, not because I have a doubt about the answers, but rather because the ECM costs nearly $2,000 to replace, and when I think of what a nightmare was the plug accessing part of the sensor replacement procedure (described here if it can be of any use), because it is under the carpet, I think it takes taking the whole interior apart to replace the wiring, which will certainly also cost $2,000 if not more. And if by pure coincidence, the new sensor was faulty, even if it is an OEM one, it would need replacing again and this would cost around $1,200, because I'm not doing it myself again any time soon (you'll understand why if you read my description).
I also found a procedure to reset the ECU by removing 2 fuses. As in many videos, I saw that after changing the sensor, if it was the cause of the problem, the CEL just goes off instantly so I had a doubt. I was right, it came back after half a km.
So either way I'm screwed up. ****. I now know there will be no cheap nor OK-costing fix. I just hate the fact the code couldn't come on when I had it inspected. I would never have bought it in the first place knowing what it involves.
Too me it kind of sounds like a plugged up catalytic convertor. If you have one of the temperature probes, probe the cats while it is running and see if any are overheating.
Why not take it to a good independent mechanic with a very good scan tool. 1 hours labor should suffice, tell him to monitor the o2 sensors, and make sure they come up to temperature properly.
reprogram the code out if the ecu cost more than the car worth it?
I didn't know it was possible. As the problem doesn't affect much how the car works, why not. The car only has 157,000 km, maintained at the dealership and is worth about $11,000 here in perfect cosmetic and mechanical condition, but I'm not far off because I've already had to replace rear brakes + callipers, a bearing, a parking sensor and the headlights. Remain the TPMSs + winter tires so I most likely will exceed its value, already without fixing the CEL.
So I'm either married to it, or forced to sell it for nothing because nobody will take it at a decent price with the light on. The former being not the worst situation because the car works great, but it destroys my plans to sell it in a few months for a facelift GS350 to put an Android Auto unit in and gain some power and options.
Originally Posted by ibidu1
Too me it kind of sounds like a plugged up catalytic convertor. If you have one of the temperature probes, probe the cats while it is running and see if any are overheating.
Why not take it to a good independent mechanic with a very good scan tool. 1 hours labor should suffice, tell him to monitor the o2 sensors, and make sure they come up to temperature properly.
I don't understand why a code for the heater circuit would come up and not for the sensor data themselves, or a code for the catalytic converter, because codes exist for that purpose. I also mainly do highway. But yes, taking it to a shop will be mandatory. I just arrived at the end of my finances by replacing those goddamn headlights so it has to wait a bit.
It could be that the one side cat is so plugged up that the o2 sensor isnt registering any heat from it. A temperature probe is ideal, but you can also right after cold start raise the car and feel the pipes before it gets insanely hot. Compare the left and right cat they should have the same heat temperature. If one is hotter then the other, then more likely there blockage. Being that the sensor you have issues with is right after a cat, its plausible. A catalytic codes at times do not get triggered.
Another thing to consider and maybe try, is to ground out the sensor. get a small wire and ground out the sensor itself. A small radiator clamp around the hex nut of the sensor with a wire attached to it, with the other side connected to a ground.
Im not sure how well techstream is, because I was unable to get mine to work on my computer. But are you able to live stream each o2 sensors? Does it show the voltage? Did you try driving the car and monitoring those grafts?
The code doesn't signal a lack of heat, but a low current (<0.3A) in the resistor circuit, this is why I still believe more in a wiring or ECU problem. Yes, I have Techstream working and I checked the signals quickly after replacement, including when driving, the value is approximately the same between sensors. Btw it was the same before replacement, the sensor part was not even bad. IIRC, they send around 1V when the engine is cold, then they go down to 0. I'm going to record it again today.
Maybe try grounding out the negative wire in the harness of the o2 sensor. If the voltage picks up then theres your issue. More likely it will be black wire in the loom.
I'll have to figure out how to try that. Splicing a wire can have bad consequences, especially with the roads beginning to be salted in a month or so. The O2 sensor is really close to the ground.
Anyway, I could feel the left sensor area was slightly less hot than the right side, during the cold start. Then, I recorded the signal during a drive:
Ok awesome so the techstream does show a lot of good data.
The one thing that popped up to me is the battery voltage, 13.3 is pretty low for a car thats running. I think it should be around mid 14 volts running. At 13.3 the alternator is barely charging your battery, so you are still able to start the car. Have you ever replaced your alternator? I would test that first before attempting to fix the o2 sensor, because that may relate to your problem.
08-27-20, 09:19 AM
SOLVED - O2 sensor heater control circuit fuse?
