I got a CEL code 21 for O2 sensor, i swapped out the old 1jz for a 7mgte sensor and soldered them together. I used a voltmeter to check for continuity and voltage and im getting both. My voltmeter is reading 0.004~0.005 am i suppose to be getting 0.5 instead? thanks in advance
O2 sensor issue 1jzgte
- Thread starter chris_2jz
- Start date
Yea i bought one to but i need a spot to put it im already using my weld on bung for my wideband i have to go get my other one welded on. Im just not sure if its suppose to be 0.5v or 0.005v. and if it is working then why am i getting a CEL for something that is working? Even when i pull the EFI fuse and then put it back on its comes on without me even turning on the car.... Not sure if thats normal or not???
Ok imma try and go in a different direction with thing thread.....
So what i would like to ask is
What would cause my ecu to give a CEL code 21 if i reset it and it comes on without me even driving. The moment i reset my ecu and turn the key on ACC it will already be blinking giving me a CEL code21 even though i just reset it.... any help will be appreciated.
So what i would like to ask is
What would cause my ecu to give a CEL code 21 if i reset it and it comes on without me even driving. The moment i reset my ecu and turn the key on ACC it will already be blinking giving me a CEL code21 even though i just reset it.... any help will be appreciated.
My Thread from November.
Never got any response. Still have the problem, I've run tests with 3 different ECUs and 2 known good O2 sensors. I have some time today & will put O'Scope on output from O2 to confirm voltage, but I recall it's .5V and varies with 'engine performance'.
I'm just finishing the wiring on my 1JZ. Have a problem with O2/ECU. It's been running very rich and fouling the plugs & O2 sensor. It continuously throws a code 21 - O2. It is impossible to confirm that it clears, because as soon as the key is turned ON, the code (21) is present.
All O2 wiring has been triple checked, O2 replaced, voltages checked. Old and new O2 both have signal output within specs when warmed up. Positive voltage present on O2 heater circuit as soon as key ON. It never gets a signal ground from ECU to actually energise the heater circuit.
Dr. Tweak told me he doesn't think the ECU will throw a code 21 (O2) just because the heater circuit between the ECU and the O2 is bad. He was not positive, but said he thought that the actual signal from O2 to ECU has to be missing.
Looking for confirmation/second opinion. I trust Dr. Tweak, but have no way to confirm. I would appreciate confirmation from other owners and possible solutions.
Never got any response. Still have the problem, I've run tests with 3 different ECUs and 2 known good O2 sensors. I have some time today & will put O'Scope on output from O2 to confirm voltage, but I recall it's .5V and varies with 'engine performance'.
I'm just finishing the wiring on my 1JZ. Have a problem with O2/ECU. It's been running very rich and fouling the plugs & O2 sensor. It continuously throws a code 21 - O2. It is impossible to confirm that it clears, because as soon as the key is turned ON, the code (21) is present.
All O2 wiring has been triple checked, O2 replaced, voltages checked. Old and new O2 both have signal output within specs when warmed up. Positive voltage present on O2 heater circuit as soon as key ON. It never gets a signal ground from ECU to actually energise the heater circuit.
Dr. Tweak told me he doesn't think the ECU will throw a code 21 (O2) just because the heater circuit between the ECU and the O2 is bad. He was not positive, but said he thought that the actual signal from O2 to ECU has to be missing.
Looking for confirmation/second opinion. I trust Dr. Tweak, but have no way to confirm. I would appreciate confirmation from other owners and possible solutions.
Last edited:
Sounds like we might be having the same issue.... I can double check my reading off my wires when i get a chance and post some pictures. Weird thing is my wideband is getting reading at 14.7~15.0 when at idle so im at a lose about that one. I have a safc2 but as of now no corrections on LO settings. So either my o2 is bad or my ecu is acting up. It never happened before untill recently. On another note, my spark plugs only foul when my map sensor acts up (running rich, back smoke, terrible idle/stalling). But yes i am having the same issue after resetting my ecu without starting the car i still get the CEL 21 for o2 sensor.... unfortunately i dont know anyone with a 1jz ecu to try out so im kinda stuck on that one
chris_2jz;1807516 said:
if your afrs are rich you will get a o2 code. o2 only read .5 volt you should not see more than 1 volt if i remeber right.. if you do o2 is bad,, (dbl ck this). also afr at idle if its warmed up and bouncing 14.5- 15.0 thats what is should be doing. thats proper o2 switching..do you bye chance have after market cams in car?? i switched mine out to stock cams fixed all my afr and o2 problems,, the issue is that bigger cams do not pull make enough vaccume ,and the map sensor think the car is under load, so the car think your under closed loop , that causes the rich idle.
Prob not the problem. But if u unhook the o2 with the key on it will code. So u would have o reset ecu each time you do that. Just sayin.. its kinda like trying to get a car running that's out of gas.. may be something simple just overlooked. And did you have to lengthen the wire for o2 to run after market down pipe ? If so did you use sheiled wirechris_2jz;1808826 said:
