AFR stuck at 14.85 - HELP

[Witness]

Hello everyone,

The AFR on my accessport V3 is stuck at 14.85. I noticed the problem when it would intermittently peg at 14.85 but then work normally. I know the car isn't actually running lean and in fact is running rich for many reasons; the exhaust smells like fuel, the spark plugs are carbon fouled, my fuel consumption is really high and my LTFT are pegged at 20. This is because the 14.85 AFR is being read and trying to be corrected.

Im getting the codes:
P2187 - lean at idle
P2177 - lean at off idle
and the code for o2 sensor low voltage which I forgot the code for

I've replaced the o2 sensor already and need more ideas on what to look for. Is it possible I bought a dud o2? Is the problem with my harness?

[Vansquish]

There are two O2 sensors. If your AFR is pegged at 14.85, then it is probably your primary O2 sensor that has failed. If you only replaced the secondary, then that wouldn't have addressed the issue with the primary sensor.

Also, did you buy a new O2 sensor, or was it used? If it was the latter, there's every chance that the sensor was already fouled by the time you got it.

[Witness]

Originally Posted by Vansquish There are two O2 sensors. If your AFR is pegged at 14.85, then it is probably your primary O2 sensor that has failed. If you only replaced the secondary, then that wouldn't have addressed the issue with the primary sensor. Also, did you buy a new O2 sensor, or was it used? If it was the latter, there's every chance that the sensor was already fouled by the time you got it.

I replaced only the primary, not the secondary. It was a brand new $170 sensor

[C-love]

Have you captured logs of and/or monitored O2 voltage? I think it should be like a waveform going up and down on the primary if i recall...

If your AFR is static I would assume the signal would be as well coming from the O2 sensor.

Also, what intake are you running?

I had crazy high LTFTs (15-20) w/ the MSCAI, adding the air straightener brought it down to 5 in less than 5 min idling. My exhaust wreaked of gas too, super rich.

[Witness]

Originally Posted by C-love Have you captured logs of and/or monitored O2 voltage? I think it should be like a waveform going up and down on the primary if i recall... If your AFR is static I would assume the signal would be as well coming from the O2 sensor. Also, what intake are you running? I had crazy high LTFTs (15-20) w/ the MSCAI, adding the air straightener brought it down to 5 in less than 5 min idling. My exhaust wreaked of gas too, super rich.

I have not captured logs of or monitored o2 voltage. Can I do that through my AP?
And I think my LTFTs are so high because for some reason my ecu is reading an AFR of 14.85. If the problem was with the AP for example, the car would run normally because the o2 sensor is actually working, but the AP is not.

[Vansquish]

The AP is not the problem, though your tune could be an issue.

Could you please post a full list of your modifications? That may help us assist you in diagnosing your issues. In fact, if you could put your full mod list in your signature, that would streamline future diagnoses.

[Witness]

Originally Posted by Vansquish The AP is not the problem, though your tune could be an issue. Could you please post a full list of your modifications? That may help us assist you in diagnosing your issues. In fact, if you could put your full mod list in your signature, that would streamline future diagnoses.

yeah lol that would help

[Vansquish]

OK, and if I recall correctly, you're running a Cobb OTS stage 3 93 tune.

That tune is, at least theoretically, reasonably appropriate for the modifications on your car. So...

That brings us back to electrical issues (i.e. sensor/wiring harness/harness connections/etc.).

You might want to check out this thread: AFR stuck at 14.85

There are a couple of possible solutions in there, ranging from replacing a bad fuse or changing spark plugs, to having to replace the ECU.

As a place to start, you might want to try checking the ENGINE BAR fuse.

[C-love]

Where do we get our AFR data, is that not from the 02 sensor?

[Witness]

Originally Posted by Vansquish OK, and if I recall correctly, you're running a Cobb OTS stage 3 93 tune. That tune is, at least theoretically, reasonably appropriate for the modifications on your car. So... That brings us back to electrical issues (i.e. sensor/wiring harness/harness connections/etc.). You might want to check out this thread: AFR stuck at 14.85 There are a couple of possible solutions in there, ranging from replacing a bad fuse or changing spark plugs, to having to replace the ECU. As a place to start, you might want to try checking the ENGINE BAR fuse.

I took a look at that thread before starting this one. I've replaced all my spark plugs gapped at 0.28 and checked all my fuses with a multimeter including the engine bar 3 fuse which I hoped would be blown because thats an easy fix.

Is there a thread that explains how to test if the female connectors on the wiring harness are good or bad? I'm guessing testing for continuity or something?

[C-love]

Originally Posted by Witness I have not captured logs of or monitored o2 voltage. Can I do that through my AP? And I think my LTFTs are so high because for some reason my ecu is reading an AFR of 14.85. If the problem was with the AP for example, the car would run normally because the o2 sensor is actually working, but the AP is not.

I'd imagine this is possible, although I haven't got to play w/ my accessport yet. My simple OBD2 Bluetooth adapter had this ability so I would be shocked if the AP did not. I'd definitely want to start there to be sure you're getting valid readings from the O2 sensor.

[Witness]

Is it possible the person at autozone sold me the wrong o2 sensor?
Could someone tell me what the part number is for the primary o2 sensor for a gen 1 ms3?

[LenSpeed6]

you might want to return that, drop more coin and get an oem sensor.

[Witness]

Originally Posted by LenSpeed6 you might want to return that, drop more coin and get an oem sensor.

cant return it because I've installed it already and drove with it on. So that was $200 that could've gone towards a tune.
Anyone know which one I should get from rock auto? They have many options.

[C-love]

I feel like you might be jumping the gun here, have you made any efforts to see if there is valid sensor output yet? Beyond the AP or a BT adapter you can probably back-probe a connector.

[LenSpeed6]

So correct me if I'm wrong but isn't there a bunch of threads stating to stay away from aftermarket O2 sensors? Maybe it's just me and I'm full of shit but keep wasting time and money on a different aftermarket ones or just buy an oem one and be done if that is indeed your problem. I get it they are expensive and it'd be nice to put that money on towards a tune.

[Witness]

Originally Posted by LenSpeed6 So correct me if I'm wrong but isn't there a bunch of threads stating to stay away from aftermarket O2 sensors? Maybe it's just me and I'm full of shit but keep wasting time and money on a different aftermarket ones or just buy an oem one and be done if that is indeed your problem. I get it they are expensive and it'd be nice to put that money on towards a tune.

I actually want an OEM sensor, not after market. When I went to the store, I asked for OEM and they gave me an NTK. So my question is, how do I go about getting an OEM sensor? I heard denso is the OEM one but Im not sure.

Originally Posted by C-love I feel like you might be jumping the gun here, have you made any efforts to see if there is valid sensor output yet? Beyond the AP or a BT adapter you can probably back-probe a connector.

I might be jumping the gun, but I have no idea how to back-probe the connector to check for valid sensor output.

[tegxsi]

NGK/NTK and Denso are fine.

[Witness]

Originally Posted by tegxsi NGK/NTK and Denso are fine.

so this means either I bought a dud or the problem is with the harness or ECU (?)

[Vansquish]

Could you post a couple of datalogs including some at idle, and at least one WOT log from ~3000rpm to at ~6000rpm?

[C-love]

Originally Posted by Witness I have not captured logs of or monitored o2 voltage. Can I do that through my AP? And I think my LTFTs are so high because for some reason my ecu is reading an AFR of 14.85. If the problem was with the AP for example, the car would run normally because the o2 sensor is actually working, but the AP is not.

To setup your parameters to log (be sure to select o2 sensor options):
https://cobbtuning.atlassian.net/wik...talog+Monitors

And to log:
https://cobbtuning.atlassian.net/wik...How+To+Datalog