# 280zx o2 sensor+ecu



## 280zx (Jan 1, 2011)

how can u tell that the ecu is recieving the o2 sensors signal. i have tested the brand new oxygen sensor and it reads a normal .45v . and i read online that there is a little green light under the ecu that is lit up when the ecu is using the o2 sensors signal. mine is not lit up. what could be wrong?


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## 280zx (Jan 1, 2011)

the car is a 1982 280zx NA. runs rich


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## skittle (Apr 27, 2010)

check the timing first of all. Also check for any vaccuum leaks. I would save the money that nissan will charge you to test the ECU. 

There are alot of other things that can contribute to it running rich. The Ecu would be the last thing.


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## 280zx (Jan 1, 2011)

timing is perfect and i replaced all vacum lines and the intake manifold gasket when i bought the car so im almost 100% positive its not a mechanical problem. this forum is directly related to '280zx o2 sensor signal problems. help?" forum.


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## skittle (Apr 27, 2010)

have you checked the CHTS?


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## 280zx (Jan 1, 2011)

the Custom Home Theatre System? im sorry i dont know what that is haha


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## 280zx (Jan 1, 2011)

is that related to the EGR?


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## 280zx (Jan 1, 2011)

cylinder head temp. ok ya ive taken a look at almost all of the sensors on the engine and cleaned em up with degreaser. they shine like gold now but didnt notice any difference in performance.


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## Shadao (Aug 14, 2007)

280zx said:


> cylinder head temp. ok ya ive taken a look at almost all of the sensors on the engine and cleaned em up with degreaser. they shine like gold now but didnt notice any difference in performance.


chances are you cleaning of the sensors did very little to help them...

some quick and simple google searcing has given me a lil bit of useful info...

there is no way to tell if you have cleaned them up properly and there is no gauruntee that cleaning them will fix your problems... also most people are either using carb cleaner rather than engine degreaser, and some use lemon juice...

the carbon that builds up on the exterior of the sensor can be cleaned off using some carb cleaner and a wire brush... however... the carbon build up on the outside of the sensor isnt usually hte problem, its the stuff inside it that most solvents cant/wont break down... and you cant brush that out...



> However, as stated, even if you get it clean, there are no guarantees that it will restore the sensors accuracy. The only way you can do that is to replace the sensor itself. And remember, there are other expensive components that depend on that O2 sensor working properly. Some of these components are the catalytic converters (if the sensor fails, the converter have to deal with the elevated fuel levels and/or elevated heat), but the engine can also be damaged by rich operation over an extended time. It is much cheaper to replace the sensor with a new one, than to attempt to clean a dirty sensor, call it good and end up replacing cats down the road. Its an easy choice, replace a sensor, or replace a sensor, catalytic converters, clean the engine, and waste money on the cleaners you used to clean the sensor after spending X amount of time wasting fuel because the sensor was so far off.
> 
> Sooner or later you are going to get stuck with replacing the sensor.
> 
> ...





> Most of you are incorrect about what to use on an OX sensor.
> An OX sensor is based on a ceramic substrate and depends on oxygen "migration" through the substrate to generate a voltage for feedback to the PCM in proportion to what it finds in the exhaust flow.
> It normally must operate at exhaust temperatures in excess of 600° to output it's intended varying voltage for the PCM to use.
> Two major types of conditions could exist.
> ...


there are a couple posts from some different forums on cleaning o2 sensors...

from what i have read the only sensors that are seemingly able to be cleaned/rebuilt are MAF sensors... the rest are a throw away item that should be replaced...

so perhaps one or more of the other sensors you have cleaned was fookered either before or after you cleaned it... and the cleaning either did nothing or made things worse...


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## skittle (Apr 27, 2010)

Ohm test the CHTS, or you can also unplug it while the engine is at idle. If it changes then most likely thats not the issue. 

Its very noticable when that happens.


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## 280zx (Jan 1, 2011)

my chts sensor was bad and i replaced it with a (almost new) one from my partscar. the car runs a lil better idle wise but is still using more fuel than it should i used some break parts cleaner instead of the carb stuff cause honestly i thinks its almost the same stuff. and as far as the CAT goes i bypassed mine years ago and the 280zx does not have any downstream O2 sensors anyway. even if it did this would not contribute to the fuel-air mix being changed, O2 sensors after the CAT are used to see if the CAT is still working not for engine managment, the only ones ive heard of that actuallly affect engine performance are brand new Jag and Mercedes cars


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## 280zx (Jan 1, 2011)

so it has a brand new 02 sensor, (less than a month) a functioning chts sensor, all the sensors on the intake manifold have been replaced b4


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## 280zx (Jan 1, 2011)

here's my real Q. say my engine is running in top notch condition with no signs of wear on any parts at all. Brand New. and one day the little green LED under the ECU goes out. what part do i replace to get this sensor signal indicating light to come back on. assuming i have already replaced the O2 sensor?


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## 280zx (Jan 1, 2011)

oh and as far as all the qoutes on cleaning 02 sensors. i completly agree and i never tried to clean any 02 sensors because its brand new, sry if i did not previously state this, i was cleaning pronged sensors on the wiring harness


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## skittle (Apr 27, 2010)

have you done the afm "rebuild"?


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## Shadao (Aug 14, 2007)

280zx said:


> my chts sensor was bad and i replaced it with a (almost new) one from my partscar. the car runs a lil better idle wise but is still using more fuel than it should i used some break parts cleaner instead of the carb stuff cause honestly i thinks its almost the same stuff. and as far as the CAT goes i bypassed mine years ago and the 280zx does not have any downstream O2 sensors anyway. even if it did this would not contribute to the fuel-air mix being changed, O2 sensors after the CAT are used to see if the CAT is still working not for engine managment, the only ones ive heard of that actuallly affect engine performance are brand new Jag and Mercedes cars


be very careful using brake cleaner that stuff is VERY dangerous... 

when heated it gives of phosgene gas and that shit is very lethal in very small ppm so be very careful using it


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## 280zx (Jan 1, 2011)

when i bought the car i traded out the throttle body for a cleaner one off of my 83 parts car. the rubber wasnt as hard and had a lot less scratches. so the afm works fine. everything on that parts car aside from the steering rack and pinion works perfect


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## 280zx (Jan 1, 2011)

sry ,ment to post that elseware. and ya im pretty carful with it


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## 280zx (Jan 1, 2011)

the whole throttle body and afm is off of my 83 parts car. the rubber was a lot softer and the whole thing was in a lot better shape. everything on that 8 worked perfect until it was crashed so im almost positive it works fine. ive cleaned the throttle body and all that good stuff


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## 280zx (Jan 1, 2011)

its an almost new throttle body


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## 280zx (Jan 1, 2011)

yes, its actually a totaly rebuilt throttle body and afm sensor of of a 83 parts car


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## 280zx (Jan 1, 2011)

yes, new throttle body and sensor off of a 83 parts car


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## 280zx (Jan 1, 2011)

haha wow i feel dumb. i thought this was a messed up thread, didnt relize it just changed pages. sry guys. posted the same stuff a couple a times, couldnt get it to work..


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## smj999smj (Jan 1, 2006)

Oxygen Sensor 


Disconnect the oxygen sensor pigtail and connect a suitable high-impedance VOM with the positive lead on the pigtail and the negative lead to a good ground. 
Start the engine and let it warm up. If equipped with an air injection system, disable the system so as not to get false tailpipe readings. 
Grab the disconnected wire that goes from the oxygen sensor to the ECU with one hand. With the other hand, touch the negative battery post or a good ground. The readings should increase on the VOM up to approx. 1 volt and there should be an increase in tailpipe CO. 
Move your hand from the ground side to the positive post of the battery. Your body will act as a proper resistor and allows a small voltage to the ECU. The VOM reading should fall to almost 0 volts and the CO reading at the tailpipe should go down. 
If the tailpipe readings acted accordingly but the VOM readings from the oxygen sensor did not go up and down, the sensor is defective.

Mode I (Exhaust Gas Monitor)
This is normal vehicle operating mode. Green LED will indicate loop status. If Green LED is not blinking, vehicle is in open loop or a fault exists with oxygen sensor or sensor circuit. If Green LED is blinking, vehicle is in closed loop. If a malfunction occurs in Mode I, Red LED and MIL (CHECK ENGINE light) will illuminate, indicating an engine control system malfunction has occurred.


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## 280zx (Jan 1, 2011)

I tested the " brand new " high quantity Bosch 02 sensor and it works fine I even tested it one my friends car cause they use the same one. As far as the green LED it's always off, never blinks or never stays on continuously


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## 280zx (Jan 1, 2011)

I have no check engine light, so possibly could the LED just be bad, OR could there be a break in the wiring to the Ecu from the sensor? Where's does the o2 sensor line up with the Ecu so I can just straight wire it?


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## Shadao (Aug 14, 2007)

i wonder if the CEL has been removed... i know of some shady people out there that have removed the CEL so they could sell a car with no CEL problems...


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## smj999smj (Jan 1, 2006)

Pretty sure they didn't have a CEL in 280ZX's. As far as straight wiring the O2 sensor to the ECM, it may be a shielded wire and, if so, not a recommendation. I would first do a resistance check of the wire from the sensor plug to the ECM plug and also check to make sure there's no short to ground. As far as the pin location in the ECM connector, I would need to know a year and if it's turbo or not. As far as the LED, it's possible that the LED burnt out or possible that it's staying in open loop. I believe it bulb checks when the key is first turned on, engine not running.


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## 280zx (Jan 1, 2011)

Ok il check the LED, and I'm almost positive it's in an open loop right now


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## 280zx (Jan 1, 2011)

1982 280zx na


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## 280zx (Jan 1, 2011)

And the 280zx "almost" has a cel, it's only used to makesure that all lights work, hi beams, washer fluid and blinkers r functional


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## 280zx (Jan 1, 2011)

should i just invest 30 bucks and buy a junkyard ECU to eliminate that as a possible problem?


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## 280zx (Jan 1, 2011)

how do i know if the LED isnt just burnt out? how do i test for that other than seeing if it blinks 5 times when key is turned


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## 280zx (Jan 1, 2011)

ok i took the LED out and put it back in and now its works. when i turn the key to 'on' the green LED blinks once and then i start the car and it stays out for the rest of the time. never lites up again. so im assuming its in an open loop feeding it way to much gas


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## 280zx (Jan 1, 2011)

i adjusted the efie and now my computer is in a closed loop on the O2 sensors signal, i leaned out the MAF 3 clicks and now the car runs better but i still think im using to much gas


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## skittle (Apr 27, 2010)

Just so you know these cars don't run MAFs. They have whats called an AFM (air flow meter). All it does is meter the airflow into the intake. A MAF (Mass air flow) measures the amount of air flowing into the intake. While it sounds the same the MAF is actually more accurate than the AFM. 

If you want to get rid of the AFM (good idea) is to upgrade to a aftermarket efi. The cheapest and the best is Megasquirt. It gets rid of the stock ECU and the AFM. You can control fuel as well as spark and tune it with a laptop.


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## 280zx (Jan 1, 2011)

ite thanks il look into that, and your right its just a AFM i turned it 3 clicks leaner but thats not really fixing the problem haha


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## 280zx (Jan 1, 2011)

ive been looking into mega squirt, i think its exactly what i need! im still investigating but can u tell me anything else about this? which oneto get or a good place to buy? is buying a used one ok?


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## 280zx (Jan 1, 2011)

somone told me an easy way to control air-fuel would be to go carburator, i love carbs and have done a lot of work on dirtbikes and motercycles so i know a lot about em, i really like the idead of using the old triple aces manifold on the 240z but would everything line up with the L28? and if it would i would definatly be buying bigger newer carbs


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## 280zx (Jan 1, 2011)

anyone know of it being done succesfully with benifits?


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## skittle (Apr 27, 2010)

I had MS on my old turbo swap. 

check out for info on the MS setup http://www.zcar.com/70-83_tech_discussion_forum/how_install_megasquirt_and_spark_886469.0.html


Now for carbs, yes they will bolt on with no problem. Now tuning them is not so hard either. The hard part is getting the right jets and needles for what you are looking for. Tripples can run from $800-$1500


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## 280zx (Jan 1, 2011)

thanks skittle


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## 280zx (Jan 1, 2011)

i have modified my afm to let in more air, but at the same time give less fuel-volts to the ecu. flap is loose like it was when u have it set to run lean but i soldered a new metal arm that sets back the voltage by 1.1 at every rpm range


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