Primary TSX O2 sensor

FlashPro questions & answers specific to the 2007-2008 US TSX
PR8urvtec
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Primary TSX O2 sensor

Post by PR8urvtec »

Is the factor primary o2 sensor a narrow or wideband o2 sensor on a 05 tsx?

I'm having an issue where my plx wideband gauge reads a lot richer then the ecu does. I do not have the wideband wired to the ecu. It's independent. Not sure what is going on with it. The ecu is trimming fuel at idle and it's saying it's trimming the a/f to 14.7 but my plx gauge is reading 12.8 a/f. Bought a new Bosch wideband sensor and it's reading the same as the old one. I don't know which sensor to believe. It's a turbocharged k24a2 (stock) and we tuned it using the stock sensor. Seemed to work fine. Datalog shows 11.5a/f in boost which was the target. 1000cc Injectors are at 85% duty cycle at psi with pte6466 turbo. I know not having the return line is going to work the injectors harder and will increase the work the injector is doing. But I'm confused as to why the sensors are reading so far off from each other.

Thanks for any suggestions.
PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

I also wanted to know if the RSX/EP3 primary sensors will work with a TSX? There seems to be a lot of conflicting information about this topic. Thanks for any help.
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Spunkster
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Re: Primary TSX O2 sensor

Post by Spunkster »

Where are the sensors located?
PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

They are right passed the bend on the downpipe. More then 24" passed the turbo. The sensors are a few inches from each other.
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Spunkster
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Re: Primary TSX O2 sensor

Post by Spunkster »

I do not believe that the sensor is the same as an RSX.

If it is open as in the picture then it may be getting air as the exhaust pulses.
PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

The exhaust is closed up. That's the only picture i had to reference where the sensors are located.

I didn't think the rsx sensors are the same. I do know the tsx has a wideband though. I'm just trying to figure out why I have such a discrepancy in readings. I'm going to swap in a known working plx unit from my other car and see if there is a difference to rule that out.
PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

Swapped out my sm-afr module with my other one that is known working and still got the same a/f reading from the gauge. Don't understand how I can have two different
A/f readings when the sensors are right next to each other. The with two different modules and two good wideband sensors.
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Spunkster
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Re: Primary TSX O2 sensor

Post by Spunkster »

Is this just a datalogged reading on the software form the PLX, or a reading on the PLX gauge itself?
PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

This is on the plx gauge itself. I don't have it tied to the ecu at all since we are using the stock wideband to tune from. It's simply to monitor things after the tune. I'm going to replace the stock primary sensor today and see if maybe the primary is not giving the right readings. It is expensive for the denso sensor but I've never replaced it since I purchased the car and I have no idea how old it is. I did open a ticket with plx support to see if they have any suggestions. I redid the wiring and measured voltage on the plx unit and there doesn't seem to be a discrepancy from the module to the gauge. When I unplug the sensor, the gauge reads 14.6-7 and then goes lean like it should.

My tuner did feel like we had to add a alot of fuel to reach the desired a/f based on the stock o2 sensor readings. At 85% DC on 1000cc Injectors, 300lph fuel pump at 10psi with a 6466.
PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

OK so a bit of an update. I ended up pulling the trigger on a new Denso wideband to replace the old OEM Denso sensor 234-9066 and all is well as far as the plx and oem sensor matching a/f readings. Now the problem is the DENSO sensor will not keep a stable af at idle. Part throttle it does hold a stable a/f at 14.6 but when idling after the engine is at operating temperature it sweeps from 12.8 - 19 a/f which my plx and ecu both confirm and the engine will bog down for a second (rpm drops a 150rpm and comes back). When I disable the primary sensor the engine idles perfectly fine at 14.6-7. Leads me to believe that the DENSO sensor is faulty? I have brought it back to exchange it for a new one but had to be ordered. I'll get the new one on Tuesday.

I'm attaching a photo of how much it swings. Just seems like if the base tune is spot on then the o2 sensor should not have to trim much if any. I can attached a datalog and calibration file if needed. I have swapped the sensors around in the bungs to rule out some sort of flow issues but the same result occurs. Any ideas?
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PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

Here is the sensor plumbing into the downpipe. Figured I'd show how they are mounted since I took a picture of it.
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PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

Got a little bit of an update. Still having issues with the Denso primary o2 sensor at idle. I exchanged the sensor out for another one and it's doing the same thing where it's swinging theba/f from 12s to 16s over and over. I put a stock tsx tune on the ecu just to see if it's a tuning issue or not and it does the same thing so it leads me to believe it's a sensor issue but is odd bc this is the sensor Denso says to use and it's an authentic Denso sensor. There aren't too many parameters to change in flashpro for closed loop either. When I put the ecu in open loop, the car idles car so it's definitely a sensor problem. Thinking about wiring the plx wideband in and trying to run the closed loop function off of that sensor and see how it goes. I'm going to contact denso and see what they say about the issue. The engine bogs down during the swing back lean so I can't see this people good for people with stock engines either I'm on stock motor mounts as well.

I tried to tune the swing out a bit and was somewhat successful but it was a matter of adding resolution to the idle portion of the map and then adding a lot of fuel at lower rpm swing and pulling a lot out in the higher rpm swing. This kind of kept the swinging in the 14s but still doesn't fix it. Was more like a bandaid rather then a fix.

Any suggestions?
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Spunkster
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Re: Primary TSX O2 sensor

Post by Spunkster »

You cannot run closed loop from an aftermarket o2 sensor.

You may want to see what others with similar modifications are seeing.
PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

That's what I'm trying to do. Unfortunately, not many people mod the tsx outside of reflash or basic bolt and tunes. I'm also going to try a NTK and Bosch primary sensor to see if it's just the Denso sensors that aren't working correctly.

If only I could find a dual ecu harness to put kpro on it, I'd be much happier. It's nice to have Flashpro at least but kpro is much more favorable. I understand there isn't a large enough market for them but maybe release the wiring schematic for those of us that would put in the work to make one.

Thanks for the help.
PR8urvtec
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Re: Primary TSX O2 sensor

Post by PR8urvtec »

And after combing through the parameters I found there is no way to run closed loop off an external sensor. Is what it is.
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