Hondata S300v3 P28 4 wire O2 voltage at 3.79v

[kraquepype]

Hello,

I noticed that my O2 voltage was stuck at 3.79v. I've been fine tuning for open-loop so it hasn't been an issue lately, but I'd like to understand if my ECU is bad or if something else is going on.

I have a P28 ECU w/ S300v3

This is with a 4 wire sensor. The sensor is enabled in the calibration, with the heater enabled as well. Nothing seems to change the voltage reading from 3.79v.

I've also swapped the sensor, disconnected it, and also disconnected the sub-harness entirely, and it still reads only at 3.89v

[Spunkster]

Is this a wideband, and if so what input are you using?

[kraquepype]

This would be the stock sensor. I have a wideband but its on D14 and is working fine.

I want to use the stock narrowband for close loop.

[Spunkster]

The stock narrow band input is D14, You cannot have 2 things on the same input.

You should use D10 for the wideband, as D14 cannot see the full voltage range.

[kraquepype]

Oh my bad, I have the wideband on D10 (ELD), I have the resistors removed and ELD disabled / disconnected and its working fine now and within .05 accuracy.

The narrowband is still on D14 - this is the one that I am concerned with now, as no matter what I do it read 3.79v constantly.

This is intentional, as I only want the wideband for monitoring/tuning. I want to use the narrowband for closed loop - it was setup that way for a while but I noticed sporadic leaning out at lower speeds and some O2 sensor errors, and I noticed the voltage stuck at 3.79v.

I've been in open loop since that and have tuned it pretty well but I would like to have closed loop working again at some point.

My guess is something is shot in the ECU but I wanted to rule out any other possibilities before I move onto that.

Thanks for the feedback

[Spunkster]

You will be much better off just using the wideband signal for closed loop. A narrowband sensor is not very accurate.

[kraquepype]

Perhaps, I would still like to understand if me ECU it messed up in some way.

I have also had reliability issues with the PLX hardware, so I would like to avoid relying on it for closed loop. Factory wiring with a narrowband O2 is my preference.

[Spunkster]

Please post the calibration as well as a datalog showing the issue.

[kraquepype]

I changed O2 sensors a few days ago. It was still at 3.8 when I changed them, but after some time its no longer stuck at 3.80v, but now the voltage is all over the place, but under 1v. It should be around .5v when the AF is at 1 right? This is with a brand new Denso 4 wire O2 sensor. Its still in open loop.

Here is my current calibration and some logs - the older one (1012_01) is when it was stuck at 3.80v, the newer one is with the new sensor and the lower voltages.

b16b_rdx.skl

rdx_1012_01.s3d

rdx_1014_01.s3d

[Spunkster]

Your calibration is set to run in open loop.

[kraquepype]

Correct, but open/closed does not seem to affect the voltage reading. Those datalogs are from openloop as well.

Should being in closed loop change anything regarding the voltages read? In my testing it did not.

[Spunkster]

If you input the wideband signal, do you get a reading on that input with the correct settings in the calibration?