Want to simulate narrow band

[DeXteR]

I have an Innovate wideband that I am using to replace the factory O2 sensor on my zenki S14 SR20DET. As such, I need to send the narrowband signal to the ECU to maintain proper operation.

Maybe the heat is getting to me, but I'm not certain which pin I need to send the narrow band signal to. Here is the FSM schematic for the O2 sensor.


I don't understand the "H" and "S" on pins 115 and 29 at the ECU. Obviously the signal goes to one of these, but which one? Also, what should I do with the other, cut and tape or ground it?

I've searched a few forums. There seems to be a lot of people who talk about doing this, but I can't find any guidance. The rest of the FSM is kind of vague mentioning inputs and outputs without mentioning from and to which item (ECU or O2).

Thanks.

[DeXteR]

So after looking at it and thinking about it and doing a little bit of research, I THINK I need to simulate the signal to pin 29 and just remove pin 115.

Can anyone confirm this?

[IanS]

H is heater control, S is signal.

Make sure you share the signal ground between the LC-1 and the sensor ground of the ECU or you may end up with a signal discrepancy. The LC-1s are notoriously finicky about their grounds.

[Hijacker]

Looking at the flow chart, I would say that the white shielded wire is the one you want. The black one looks to be a ground for the heated side and the ECU controls when it's on/off unlike the S13 style where it's internally controlled at the sensor itself.

[DeXteR]

Thanks guys. I just wanted to make sure.

It's actually the new MTX-L.

Run simulated narrow band to 29 and ground to 115. I'll let you know how it works out as soon as it's up and running.

Thanks again.

[IanS]

You may not want to ground the heater control. It may be looking for a referance voltage from the heater because it acts as its ground source. Grounding it directly may throw fault codes. Like I said on Facebook, you may want to just run a narrowband for reliability.

[DeXteR]

Goodness. I didn't think it was going to be this big of a deal...

So, looking at the FSM some more, I did find a section that mentioned checking the resistance across the heater. Here's my "duh" moment: To check the heater, you test for resistance between pins 1&3 on the sensor - that makes 2 the signal which goes to pin 29 on the ECU.

All right, so you want to see 3-1000ohms of resistance there. So is the ECU looking for a resistance or an amperage? Can I just toss a resistor between a 10amp source and pin 115 and be good? What resistance?

I bought this sensor and gauge package with the expectation that it would be a suitable replacement for a factory sensor AND allow me to monitor AFR for tuning and driving. Lot's of people use widebands in their daily drivers. Plus this one simulates narrowband so I don't need to run two sensors. Now it looks like I've opened up a can of worms and I'm not sure what to do about it.

One of the guys in my car club just told me a bunch of horror stories about these sensors failing pretty regularly. Why, though? What makes these sensors any different from an OEM oxygen sensor? These things are supposed to last 100k miles!

So I pulled up the MTX-L manual and started reading some more and found this:
"Some EFI-computers will create a fault when the heater power wires are disconnected. In this case mount the old sensor in a safe place and connect the heater wires to it to keep the EFI-computer happy."

How unhappy? Is it just going to stay in open loop mode the whole time or is it going to go into limp mode? Either way kind of sucks, but open loop is tolerable. Limp mode is barely drivable.

[IanS]

Lots of people do lots of things, doesn't make any of them a good idea.

As for the ecu being unhappy. I don't believe (not positive) that the factory Nissan ECUs have any internal logic telling them what to do in the event of a heater failure. It will surely turn the light on, but beyond that I am not sure. The S14 ECUs are different so I don't know.

[DeXteR]

Lots of people do lots of things, doesn't make any of them a good idea.

Oh, I hear you loud and clear on that note.

I'm going to go ahead and give this a try. I'm going to run the wideband without the narrowband, but I'll run the wires for the narrowband as a backup in case things don't work out.

Thanks again for your valuable insites.

[compactfean]

I personally have the s13 sr with my wideband output simulating narrow band and works just fine. As far as the heater, yes. .. Just run a resistor and it will keep the light off.

[DeXteR]

I ended up not bothering with the factory sensor or wiring at all. I installed the wideband with the simulated narrow signal going to pin 29 at the ECU. I didn't hook anything up to pin 115.

Once I got the car running, there was no CEL. I do have the warning signal hooked up, so I'm not cheating. I put about 5 miles on the car and still no issues. I'll be putting more miles on it after getting it more road worthy and report back.