problems with AEM UEGO
 

I know this problem has been beaten to death, but I'm still having issues getting MSPNP9093 to read my UEGO despite reading a ton on here.

I have it wired from the white wire on the WB pigtail to pin 10 in the center harness. (2nd from the left, bottom row when looking at the harness while plugged into the unit)
I have unplugged the stock NB from the harness behind the motor.
I went into the Megatune Configurator, and into settings.ini and changed the LAMBDA_SENSOR to AEM_Linear.
In Exhaust settings in megatune, I set the unit to read wideband, and set the switch point to 2.375 (however, after burning, if I go back in it is changed to 2.372 every time.)

I have used a multimeter to verify the voltage readings at the center harness connector are in the right range, and I get good readings on the gauge face itself.

However, no matter what I do to the motor, the Air:Fuel readout in megatune never goes above 9.72.

Anything I'm missing?

Well, I guess my next step would be to move my lead from pin 10 on the center connector over to the wire for the nb sensor currently. I sure do hate to splice my factory harness just for testing reasons though. Does anyone have any further thoughts at all?

First, right click your AFR gauge and swap it to an EGO voltage gauge. Is it stuck at 0 volts or does it move like it should?

im having similar issues, i tried what Matt said and my voltage is getting a reading but my AFR innovative gauge and MS reading dont match up

i'm pretty sure everyone with the AEM has suffered from TS and MS not reading the same figure as the gauage. I managed to improve mine the other day down to 0.2 AFR off MS by cleaning the earthing plate for the ECU and AEM(rummber the dirt of with some wet&dry paper). Best of luck with sorting it.

When the AEM UEGO controller turns on what mode does it show?
P00,P01,P02,P03,P04?

It Needs to be set to P00 for correct voltage output for AEM wideband mode 0-5v

If its on anything else, changed it to P00.

Small screw driver to the back of the wideband, there is a small hole with a turn dial, slowly twist the dial till the aem shows P00 on it. Doing this while you have your ms up and connected to MS will show your output changes on that wire.

I can easily make it show 9afr's in the wrong mode because of the voltage output.

The car has been sitting with a battery issue that I finally had time to fix (got married a few months back and bought a house, nuff said).

It is set to P00.

I have not had a chance to check the EGO voltage. I will do that shortly.

I don't see EGO Voltage as an option. I see Front Bank O2 Voltage and Rear Bank O2 Voltage called EGOGauge and EGO2gauge. Neither of those go over .25 volts no matter what I do.

Which wire in my harness is the stock O2 wire?

Any thoughts guys?

Does the wideband itself read correct afr's while on? if yes, put a multimeter on the output wire to check that its outputing correct 0-5v output. if yes, check wiring to ms

Yes and yes.

The manual says that I can wire the WBO2 to pin 10 of the center connector (which is where I have it now) or on the stock O2 wire input (splicing into the factory wiring). I want to change the input to the stock O2 input, but I don't know which wire that is on a '91, and I don't see that in the manual. That's what I'm asking at this point.

Thanks for the input.

Are you sure is not defective. Although, mine was a Innovate, it came broken from factory.

http://www.boostedmiata.com/gallery2...ne_harness.jpg
pink text saying oem nb is where the stock oem narrowband wire is and now where your wideband signal is going to.

Oooh, excellent. I'll give that a shot.

Mazpr, I don't think it's the wideband because the gauge reads properly and the voltage output on the 0-5v line appears correct.

Moved the gauge wiring to the stock narrowband wire. No difference. :(

This doesn't make any sense unless I've missed an obvious step in the MS configuration or my MSPNP is borked.

Ok, I got it. Whew.

Let's just say this isn't an issue the rest of you would ever face, so no wonder it was so hard to figure out. I traced the stock O2 sensor wire back to the firewall, and about a foot back, I found a DIY splice to the red wire to the top left of the O2 signal wire. I can't fathom any idea why a previous owner would have done this, but it would explain why I have always fought with O2 sensor problems even when the car was stock. The wideband gauge face and MS are within .1 AFRs of each other after removing that splice.