4 wire o2 hookup to 5 wire A/F sensor

T

tyman108

Member
:
02 Protege5 2.0L turbo
hello the title says most of it, im looking to replace my rear o2 with a wide band so i can also hookup a wide band gauge and not get any codes

rear o2 sensor wire
G/R - pin 93 - heater On/Off
Y/L - pin 35 - O2S12 Rear
O - pin 91 - Ground
B/L - pin 26 - ignition timing

Bosch 17025 A/F sensor
Red - IP
Black - vs
Yellow - vs/ip
white - H-
grey - H+

this is what i found out from the internet diagram. can someone please tell me what wire goes to what wire?
 
Your wideband sensor can not directly feed the ecu on your car. You need to transform the voltage signal to the appropriate voltage for the ecu. This is normally done in the gauge itself. AEM gauges have a number of output voltage settings.

All the ecu needs to see for the bank 1:2 sensor is a periodic voltage swing between .2 and .9 V to be happy.

Also you can not simply replace the existing O2 sensor with a wideband to eliminate the CEL codes.

If the ecu does not see the O2 heater circuit it will also throw a code. So you would need to leave the existing sensor hooked up also.

PM if you need more info as I have mean making a nifty plug and play O2 spoofer that can totally eliminate the secondary sensor and you will never throw another sensor 2 code again.
 
Last edited:
Where are you planning on installing the wideband sensor. It needs to go about 18 inches downstream of the bottom of your exhaust manifold.

You can just leave the existing sensor hanging somewhere in the engine bay with the heater wires hooked up.
 
So you need to measure 18 inches down the exhaust from the bottom of the turbo. This is where you should get a new bung welded. Make sure it is angled slightly upwards so water does not collect on the sensor. The ultimate position is best selected while the car is up on the hoist.

Not sure about your brand, but you will need to feed a 1V signal directly to the ecu.

You will also need to supply a specific resistance at the heater circuit or you will get a CEL unless the old O2 sensor is still installed.
 
My lower O2 sensor is toast, giving me CEL. I replaced the upper 02 sensor in April.

Does anyone know if the upper O2 sensor will still adjust the fuel/air ratio if the lower O2 sensor is gone? I replaced the upper O2 sensor for fuel economy but I'm reading the lower O2 sensor only measures emissions, then other people will say it also adjusts the fuel/air ratio. Luckily Rockauto has a lower O2 sensor for less than $45 including shipping but if it can wait a month or two or three that would be cool.
 
You can wait for the secondary O2. It will only trigger the CEL and has no effect on air fuel.
 
The Bosch wideband has a lambda voltage swing from 0-5V. Your ECU expects a voltage swing from 0-1V. The stock O2 sensor has a voltage swing of 0-1V. Therefore if you want to use the signal from the Bosch sensor you need to convert the signal range.
 
thuzil said:
You can wait for the secondary O2. It will only trigger the CEL and has no effect on air fuel.
Click to expand...

sweet

Edit: I'm reading with any CEL on, the engine will run in open-loop, meaning not as fuel-efficient. You're saying it will still run in closed-loop, relying on the 1st O2 sensor to adjust the fuel/air ratio?
 
Last edited:
Jesus Christ the confusion and wrong info here lately

1st o2 sensor monitors afrs and tells the Ecu to add or take away fuel, it is a narrowband sensor so it just throws out voltage saying good rich lean way rich way lean ( there's more to it than that but I'm using this example for simplicities sake)

2nd o2 sensor monitors exhaust gases to ensure the precat is doing its job it does nothing else

If you have an aem wide band and don't want to add a bung there should be a wire on the harness for it that emits a narrowband signal to send to the Ecu.

As for the whole 18" from turbo thing that is a myth mine is right on the down pipe a friend of mine had a 400whp dsm and his was right on the down pipe as well. If it was such a big deal oem o2 sensors would be 18" from it as well. It does however have to be 18" from the end of the exhaust

And having a bad o2 sensor won't leave it in open loop ever. Even if the first sensor is bad it will go off the maf and iat to guesstimate and add a little extra to be safe
 
Dude the only confusion introduced into this thread has been by you.

18 inches is recommended by the manufacturer for install. You can put it anywhere you want, but that does not mean it will work properly.

The guy was asking about open and closed loop. Info provided stated that the secondary 02 has nothing to do with air or fuel, so I am not sure what you were reading.
 
thuzil said:
Dude the only confusion introduced into this thread has been by you.

18 inches is recommended by the manufacturer for install. You can put it anywhere you want, but that does not mean it will work properly.

The guy was asking about open and closed loop. Info provided stated that the secondary 02 has nothing to do with air or fuel, so I am not sure what you were reading.
Click to expand...

Again, its not required. I know multiple people that have their wideband on the down pipe. If you want to get technical the reason it's recommended is so that the exhaust gases have time to mix. with the car being turbo the gases are mixed by going through the turbine wheel and do not need the 18" to mix to get a proper reading
 
No,

Mixing has nothing to do with anything. the reason is that the exhaust coming off the block has not had sufficient time to cool and will reduce the lifespan of your sensor the closer it is to the manifold.

You can mount it anywhere between manifold and your first cat and you will get the same AFR reading, you may just be buying more sensors the closer you mount it.

Before you start saying "but mine is only 3" on my downpipe and works fine" this may be the case, but the average failure rate is higher the closer the sensor is to your head.
 
Last edited:
Touch your exhaust at the manifold and then touch it18" down and tell me if you notice a difference
 
That is a pretty ridiculous comment. Exhaust temps can differ 100s of degrees from the Mani to the muffler tip. You can have over 100 F drop in a foot of piping.

But as I said before install the sensor anywhere before the cat and you will get your reading.
 
Last edited:
The only reason it would drop that much is if you have a cat. But I guess Subaru and Mitsubishi doesnt care how long their sensors last or any other manufacturer the uses a wideband sensor stock. Believe whatever you want to, you're about as hard headed as Brian
 
Please log in or register to reply here.

Similar threads

TBarney
    • Like
Guide Add paddle shifters to Gen 2 (2017 KF) CX-5 with heated steering wheel. "Easy"
2
Replies
33
Views
16K
monoski
M
J
ECU O2 sensor wiring HELP P0134 stuck in open loop
Replies
4
Views
4K
jumaaneface
J
D
Question on ECU / O2 sensor wiring
Replies
7
Views
1K
dmention7
D

Latest posts

Back