OK, I know that we can do custom tunes and chip burning on our OBD1 cars.

Is that possible with OBD2? Can it be tuned and some of the threshold levels changed to make it less sensitive to throwing trouble codes?

Thanks.

 

Yes for the most part. Just gotta see if some kind of software exists. Depends on vehicle. GM and Ford stuff can be tuned pretty easily. Hptuners for gm and some ford i think and SCT i believe for most fords. You can turn off codes from displaying but doesnt mean that fixes issues that caused codes in first place

 

Subaru.

Even the mechanics at the dealership say the thresholds are too low for catalytic converter efficiency. Once a Subie cat gets much age it starts throwing below threshold codes. I was just wondering if the OBD2 can be re-programmed to raise the threshold a bit so that we can get a few more years out of a set of cats before the CEL comes on. At smog checks, all the tech does is plug into the OBD port and read codes. No codes mean you pass, if you also pass visual.

 

Eh you might beable to disable the o2 code for that like how some gm guys delete rear o2’s from a tune but you cant tune the o2 sensor voktage threshold i wouldnt think as the pcm will control fuel around that point but i could be wrong . I dont know subs much but i do know the wrx/sti and others like that are tunable lol alot of my friends do them as well as other imports

 

Depends on the year. What year and model of Subaru?

GD

 

It happens on both my 04 Outback and the wife's 02 Forester. Both cars have the 2.5L boxer, non turbo.

Like I said, even mechanics have commented that Subaru set the thresholds too low in the software so as soon as a cat starts to degrade in the slightest, it throws a code. Cant pass smog with a current code. I was thinking to just change the threshold slightly where the code gets thrown, make it a little more forgiving.

Not long after I got the car, there was a factory recall to change the software in the ecu. I think that is where the factory tightened up the settings.

 

Don't the front O2s measure the engine mixture for feedback on the fuel settings, and the rear O2s measure how well the cats are working?

 

Neither of those years have any support in the open source community. While they do support flash ROM programming, no one has hacked them due to them not being a popular model for tuning. Generally speaking we can tune all the turbocharged models, and non-turbo models we can generally find a hacked ROM for if they are 2005+

For the 02 and 04, you can use a 90 degree spacer on the secondary O2 sensor and this will stabilize the reading enough to make the computer happy. These are $15 on Amazon. There are also some O2 spacers that have mini converters in them.

If neither of those options is suitable then you have to buy a dealer cat. To Subaru's credit I generally don't have to replace them till they have at least 150k on them and Subaru cats never plug up so at least there's no driveability issues if you need to wait a few months.

GD

 

I have read about the O2 sensor spacers. Apparently they move the sensor tip out of the direct exhaust flow which de-sensitizes them and makes them more forgiving. I may go this route, save a helluva lot of money.

Don't forget the anti-sieze when re-assembling!

 

These work:


GD

 

you can change the rear O2 sensor signal to trick the ecm. Solder a resistor in the signal wire, and a capacitor across the signal and signal ground. Smooths out the signal, ecm thinks the cats are doing their job. Did this on my 02 Toyota 3 years ago. No code came back, passed emissions each time. I’d have to look up the resistor and capacitor specs tho.

 

You can just feed the ECU a 0.7v signal from its internal 5v supply if you are going to dink with the electronics. That's all it's looking for is a flat line signal around 0.7v

GD

 

Before I start dinking with the electronics, I'll just try the spacer.

Probably should put in a fresh O2 while I'm at it, no?

 

This is correct, I have customers request this constantly. I have even drilled out a anti fouler big enough for a O2 sensor to thread inside of and then add another anti fouler to the drilled one and got the same result. Subaru does have extremely low thresholds.