[igneouss]

Trying to get my head wrapped around this issue.
I have VRSF DPs.
I have a CEL light on.
I do NOT have to pass emissions BUT I can't pass with the CEL light on. Plus I don't like having it on all the time.

1) is the DP fix option something that I install and set and then forget? It just sits there and does it's thing. No CEL light for that reason any more?

2) Does the JB4 suppress the CEL? If so is it suppressing ALL CEL or only the DP related CEL?

I've looked at lots of threads but many (most?) seem out of date or contain posts that contradict each other.

Are there simple answers to these questions in 2022?

Thanks!

[Saif2018]

Originally Posted by igneouss

Trying to get my head wrapped around this issue.
I have VRSF DPs.
I have a CEL light on.
I do NOT have to pass emissions BUT I can't pass with the CEL light on. Plus I don't like having it on all the time.

1) is the DP fix option something that I install and set and then forget? It just sits there and does it's thing. No CEL light for that reason any more?

2) Does the JB4 suppress the CEL? If so is it suppressing ALL CEL or only the DP related CEL?

I've looked at lots of threads but many (most?) seem out of date or contain posts that contradict each other.

Are there simple answers to these questions in 2022?

Thanks!

Yes, if you asked in JB4 forum N54Tech,

Most of the guys here don't use JB4,

[dpaul]

As far as I'm aware, the JB4 does not suppress the CEL. It used to but I believe that feature was disabled. As I recall there remained an 'undocumented' way to turn it back on but that was quite a few years ago and I don't know the current status. As @saif2018 indicated, you'd get more info poking around N54tech.

You can install a "DP fix" - this is basically a variable resistor that takes the place of the post-cat O2 sensor and provides an approximately correct signal to the DME so it thinks the cats are in place and working.

The "DP fix" will get you through inspection but it is NOT a good idea to leave it in place. The N54 DME uses the signal from the narrow band post-cat sensors to provide an accurate signal at stoichiomentric AFR to calibrate the wide-band pre-cat sensors. If you leave the DP fix in place you will note a slow drift of your LTFTs and at some point engine operation will be compromised.

By far the simplest way to solve this problem is buy an MHD flasher licence. You can retain the JB4 if you like (details available on N54tech) and use it only for safety and convenience features or use it for those features plus boost control if you wish.

[igneouss]

So, DP Fix is not an permanent fix, only a fix for short term use.

JB4 no longer corrects the issue.

How about MHD?

[F13.KENN]

Originally Posted by igneouss

So, DP Fix is not an permanent fix, only a fix for short term use.

JB4 no longer corrects the issue.

How about MHD?

Correct. Previous owner left one installed on my car and my o2 readings were very out of wack. They did also put stock dp back on while leaving the fix on and activated….

Mhd is set it and forget it. The cat codes will still pop up but it will be as a shadow or "not active" code. CEL will be off.

Mhd > jb4 in my opinion. Have had both

[dmckmc]

I use both MHD/JB4. Info all correct as stated in posts. JB4 - will NOT hide/disable check engine light in USA. MHD - will keep light from showing on dash but cat codes are present if scanned for and will not pass emissions as cats will never be 'ready'. I use DP fix only temporarily during emission check time. TunerPro is often used to toggle/disable the codes to keep light off on dash. Emission computers can see if emission parameters are tuned out and you will not pass (happened to me!).

[dpaul]

Originally Posted by dmckmc

I use both MHD/JB4. Info all correct as stated in posts. JB4 - will NOT hide/disable check engine light in USA. MHD - will keep light from showing on dash but cat codes are present if scanned for and will not pass emissions as cats will never be 'ready'. I use DP fix only temporarily during emission check time. TunerPro is often used to toggle/disable the codes to keep light off on dash. Emission computers can see if emission parameters are tuned out and you will not pass (happened to me!).

Just a small addition here - whether you pass with one OBDII monitor 'NOT READY' is a state-by-state issue. In MA, no problem. In CA, no chance. It should be possible to make the determination by careful reading of the RMV regulation for your state.

The only thing emission computers can assess about your tune is a checksum value called the CVN (which in fact can be faked quite easily). Emission computers cannot ascertain if you have disabled monitor checking, only if a monitor is "NOT AVAILABLE, "NOT READY" or "READY". As far as I know, only CA is currently looking at the CVN but I could be wrong about that.

Finally, all bets are off if you are flagged for one reason or another and forced to complete your inspection at a state-run facility. If that happens in MA, you are dead. They will visually inspect, find your missing cats and fail you.

[dmckmc]

Originally Posted by dpaul

Just a small addition here - whether you pass with one OBDII monitor 'NOT READY' is a state-by-state issue. In MA, no problem. In CA, no chance. It should be possible to make the determination by careful reading of the RMV regulation for your state.

The only thing emission computers can assess about your tune is a checksum value called the CVN (which in fact can be faked quite easily). Emission computers cannot ascertain if you have disabled monitor checking, only if a monitor is "NOT AVAILABLE, "NOT READY" or "READY". As far as I know, only CA is currently looking at the CVN but I could be wrong about that.

True that states and even counties are all different. In my county I was Emission Failed for: "Cat. Conv. & O2 Unsupported Programming Error" because I toggled off several emission warnings via TunerPro.

[igneouss]

It varies by county here in VA. I live in a county that does not require emissions testing. I do not believe they plug anything in to the OBD port during the inspection.

I am slowly learning a lot here.

New question: If you have a JB4 with an MHD BEF will that suppress the CEL light? Or do you need the full MHD flash tune to get that benefit?

[dpaul]

Originally Posted by igneouss

It varies by county here in VA. I live in a county that does not require emissions testing. I do not believe they plug anything in to the OBD port during the inspection.

I am slowly learning a lot here.

New question: If you have a JB4 with an MHD BEF will that suppress the CEL light? Or do you need the full MHD flash tune to get that benefit?

If I remember correctly JB4 BEFs as provided in the N54tech links do not come with cat monitor disabled. Again, could be wrong about that. However, it is simple enough to modify them using tunerpro (which is freeware) and an appropriate XDF file (https://github.com/dmacpro91/BMW-XDFs).

[dpaul]

Originally Posted by dmckmc

True that states and even counties are all different. In my county I was Emission Failed for: "Cat. Conv. & O2 Unsupported Programming Error" because I toggled off several emission warnings via TunerPro.

Out of curiousity, if you don't mind, what state/county are you in?

[igneouss]

Originally Posted by dpaul

Out of curiousity, if you don't mind, what state/county are you in?

Virginia, Warren County (near towns like Front Royal and Winchester, near I-81). Virginia requires emission testing in urban areas like the D.C. suburbs and Norfolk/Virginia Beach. Maybe a few other areas. But not in the rest of the state.

[dpaul]

Originally Posted by igneouss

Virginia, Warren County (near towns like Front Royal and Winchester, near I-81). Virginia requires emission testing in urban areas like the D.C. suburbs and Norfolk/Virginia Beach. Maybe a few other areas. But not in the rest of the state.

Sorry for the confusion, I was actually asking about the location of @dmckmc. You had previously stated you were in VA (and it's in your sig), although I was unaware that there were such significant county-by-county differences there.

[igneouss]

Maybe I should have said this earlier for clarity:
Car: 2010 335i N54. DPs, FMIC 5", Inlets and outlets, charge pipe, DCIs.
Goal: Daily Driver. Pump gas, 93 octane. Set it and forget it tuning. I am not trying to get every available HP out of it. Just reliable daily driver without having to tinker with the tuning much if any.

CEL: it's on due to the DPs. I believe I would fail inspection due to it being on. But more importantly, I would like it to function correctly, as in stay off unless it needs to warn me about a legit problem. If it's on all the time then it's not warning me about anything! Similarly, if it's suppressed then it's not warning me about other possible issues...

[dmckmc]

Originally Posted by igneouss

New question: If you have a JB4 with an MHD BEF will that suppress the CEL light? Or do you need the full MHD flash tune to get that benefit?

Using MHD to flash the JB4 provided 'BEF' tunes will keep the CEL off. There is an option to select factory or no cats in the MHD flash program. So you could buy just the 'flash' portion of MHD for this but I believe it's worth having it all to open up options for you.

To your later question about keeping the light off and possibly hiding other problems...MHD only toggles off or suppresses active codes related to the cats/DP. All other problems will still activate a check engine light such as misfires, temps, pressures etc.