Stock ECU and O2 sensor trouble (code 15,17)
 

Hi all,
So for SMOG removed MS PNP2 and put stock ECU and intake bits, removed wideband sensor hooked up to AEM AFR and put a new O2 sensor. AFR itself is hooked up to power, but wideband and IAT were disconnected, it just shows constant 14.8 or so at all times. Now getting codes 15,17 and RPMs get stuck around 1500 every time i step on the gas and then back off.

How can i test the sensor or ECU circuit for it?

I read that 4 times and still can't be certain what you're saying.

Did you install an OEM narrowband O2 sensor, and connect it to the OEM O2 sensor connector?

Yes. I bought car with MS PNP and wideband sensor. For SMOG test i removed both and put original ECU and brand new O2 sensor with 4 pin plug. Now getting codes and throttle stays open around 1500rpm instead of dropping to idle around 750rpm when i release gas pedal

should have just switched the AEM to NB mode and sent that to stock ECU -- easier and you really don't want to keep your wbo2 sensor in the exhaust without the heater circuit running on it.

but code 15 and 17 are specifically for the o2 sensor, so sounds like the stock ecu isn't getting the signal. Did the OP splice shit up to install the WBo2?

Hi Braineack, thanks for chiming in - i was hoping you would :)

I can still put wb O2 sensor back and connect to AEM. I really don't know what's the best way to handle this and how to make it work, but I'm trying to read up (although just get confused even more since i tend to over-analyze stuff). He kind of did splice stuff up since he is an electrician by trade, but most of it has been more or less reasonable without any big surprises.

Original owner just replied that he changed the connector or wiring for O2 sensor, but didn't say exactly in which place - plug or ECU side...

There is no narrowband mode on AEM widebands.

http://www.aemelectronics.com/files/...GO%20Gauge.pdf

Strange, I've read in multiple places that AEM does have a narrowband mode - here is one of the sources https://www.miataturbo.net/aem-59/ae...ock-ecu-80570/

Here is the gauge I got:

Attachment 229561

Plug on the Bosh wideband sensor that I removed

Attachment 229562

And here is what I got under the hood
1) AEM UEGO connector going to the guage
2) Old stock O2 sensor plug with wires cut off, but a single lead going from it into firewall and presumably to the guage
3) Connector between ECU and now stock/narrowband O2 sensor installed now

Attachment 229563

The way it was when I bought the car:
#1 was plugged into Bosh O2 wideband
#2 was plugged into 3
AND IAT sensor in intake was plugged into stock MAF connector via 2 wires.

p3 or p4 look like they be enough to tell ECU there's a NB in place and working:

http://tunertools.com/prodimages/AEM...structions.pdf

So what you are suggesting is to keep the Bosh WB O2, reconnect it to ECU O2 plug and then switch guage into P3 or P4 to see if it sees it and emulates a narrowband, right? This may work, but I'm worried the dude at SMOG station will fail me on visual inspection due to non-OEM configuration.

I've checked with the wiring diagram and PO wired RED/BLUE ECU wire on plug #2 in pic above to go into AEM UEGO (make sense).


Also the question why reinstalling stock ECU and connecting it via engine bay plug with stock O2 sensor isn't allowing ECU to read the narrowband sensor correctly. It just throws codes as if the sensor wasn't working. Because in my mind - this reversed all modifications that were done to install AEM+Wideband. What am I missing?

You're right on that model. I have the X-series 30-0300 which doesn't. I assumed the cheaper 30-4100 wouldn't either. Seems odd they would have ditched that feature.

yes, it's the plug that was cut off from original stock O2 sensor and it has a single pin wired (red/blue on ECU side) going through the firewall.

So anyone can point out my misunderstanding or ignorance so I can learn in regard to this:

I'm at a point where I think my next step is getting a second new sensor to see if that solves the problem. I don't see any other reasons why new O2 sensor plugged in into what appears an unmodified O2 sensor plug on the car side would not read with stock ECU.


What i've done since previous post:
- checked for continuity on red/blue wire from O2 sensor plug in engine bay to ECU
- checked fuses under hood and driver foot well
- checked for 12v on one of the black wires in O2 sensor plug in engine bay when key is turned (heater circuit)

Anyone with other ideas or suggestions?

Check voltage on the wire going in to the ecu. Signal from the narrowband should fluctuate between 0 volts and 1 volt while running.

this, read the voltage.

Ok, so I've tapped into the sensor while it's installed into the car and warmed the engine up, the voltage was all over the place. It would jump up to around 1v and rapidly go down to close to 0, then repeat over and over. I've repeated this several times to make sure i was consistent and wasn't a bad contact on DMM. I think this doesn't answer the question whether the sensor is good, so next I will pull it out and heat it while taking voltage readings.

thats normal for a nbo2

what are you trying to say here??