Does anyone know if the oem narrowband oxygen sensor works on a 0-1v scale? I am looking to install a PLX that would run both a narrowband on a 0-1v scale for close loop and a wideband for A/F testing in the same bung.

 

The OEM sensor is a typical 0-1volt narrowband style.

 

greatbear,

Thanks, i appreciate it. Would you by anychance know anything about the pin-outs on the ecu??

 

but I've found an error or two...

But one thing to know, is that the Mini uses a isolated input for some sensors.... Good luck, and if you get it to work, let me know how you did it!

Matt

 

PM me about this. I installed my plx r-300 this way last month, with narrowband simulation. The short of it is, it works. BUT, I had to chase a few gremlins.

ONE, as DR. O has said in his plx thread, the knock sensor has a separate ground and is not the right type for the plx to understand [it produces super-low voltages]. Simply put, when I tapped it [I forgot that he had warned against this!], the plx ADDED like 10x the knock voltage statically and my car freaked. It pulled all kinds of timing and operated super-rich. I cut the knock analog input that I had soldered in and re-insulated the wire, and things are great now, sans any input now for knock to the plx.

The narrowband output works well, because the car runs great. But, I'm working on ways to reduce the noise inherent in the new circuit, to make the narrowband signal as intact as possible.

BUT, there's still an issue for me with the oxygen sensor heater. The stock narrowband needs to reveal that it is 'heated up' for the car's ecu to think it's working, even if the ecu is getting a proper narrowband signal. Otherwise, it throws a CEL to say that the sensor is not functioning.

The plx manual says to trick the ecu with a 20 ohm 10 watt resistor. WELL, I got the appropriate resistors and my friend and I worked out a really elegant solution by splicing it into the former female connector [we cut the narrowband harness and inserted this into the connector]. BUT, the cel still goes off.

This is the only error I've got. I'm really busy with finals and haven't figured this out yet. I see two possibilities. One, the resistor does not provide the proper resistance [see my next post for an update]. Two, the resistors may not yet be completing a circuit as they should.

I'm still working on this issue. But, good news is that the narrowband simulation works as it should. The ecu is adapting as normal, I've lost no power, and I'm happy. Now, if only I can trick the ecu...

 

Just a minute ago, I got curious and decided to go read the resistance across the o2 sensor heater circuit. It reads between 3.6 and 4.2 ohms. That's way below what the PLX manual said would be needed [20 ohms]. I guess that's why my CEL is coming on. I'm gonna get some new resistors and hopefully that will fix things.

I've got a question, though. Given that the wires read about 4 ohms across them [but this does oscillate a little, like I wrote above!], what would be the proper resistance to go to? I'm thinking 4 or maybe 5 ohms. Any thoughts? Thanks!

 

Is look at the current and voltage when hot. That way, your resistor will mimic the load of the heater when it's at operating temp....

Just a thought...

But it's probably easier to get a 3, 3.5 and 4 ohm resistor set, and just use the one that works. Maybe ever 4.5. Resistance goes up with temp (for most things, at least).

Matt

 

I think I'll probably just go the route of "try and see," as playing around with hot wires can be bad . But, this may not be 'easy' [for the reasons below]...

About the o2 sensor heater circuit code... When I first installed the current resistors, there was no light. I drove a couple of hours, came home [turned the car off], and then set off on a 5 hour journey the next day... An hour into the journey, I stopped for coffee, and when I turned the car back on [third cycle since install] the CEL came on.

I guessed that either the circuit is kinda lazy [and it only checks/complains intermittently, ie every couple of ignition cycles] or it has some fail-safe built in and will only trip the CEL after seeing the same error a few times. Maybe both.

Well, I checked with a good friend and MINI guru in Miami, Luis Sanchez of Precision Autowerks, and now I have an idea or two about what may be happening. The o2 sensor heater circuit is there as a way for the ecu to make sure that the o2 sensor is working [so that it may ensure that the signal which it is sending the ecu is reliable...]. BUT, it seems that the heater circuit is only active for a narrow window during which the car is initially idling [and it apparently becomes inactive around the time when you begin your journey]. It is supposed to check with each ignition cycle. Since it took three cycles to get a light, I guess the car plays dumb for a while before deciding the sensor is 'bad.'

Therefore, beating this CEL may be harder than I think. After clearing my codes, I'll have to cycle the car a few times with whatever combo I try to ensure that it's working right.

Sorry for being long-winded. I hope that this helps someone .

 

with your scanner, look for a pending code after you've driven once after clearing all the codes. Some throw the CEL right away, some take 3 repeats.

The heater is to shorten the amount of time before closed loop control can be done with the sensor.....

Matt

 

Cool . Thanks, Matt . I'll be playing around, finding a fix, when finals finish. Then, I'll post back and let y'all know what resistance hits the spot .

 

ingsoc, did you ever work out how to fool the heating resistor?

 

you can just do what I did.... Add a bung and leave the stock system alone. I just use the wideband for diagnostics....

Matt

 

well i've finally taken the plunge to T/C, so i'll just have them weld in an extra bung before i install the downpipe. The issue before was that no one in my area would touch my exhaust system, and i didnt want to take out the header... but now its all changed