[peteyypab]

Hey all,

I'm just over 161k with no record of CBU or Walnut Blasting...

car runs great, 6k Oil changes, Fuel Filter every 4th oil change.

Ive owned the car since 43k and never had any CBU related codes, I've never had it cleaned and do not recall seeing it on the prior service history .

Im seeing lower overall mpg on the OBC (23mpg) and I've got 4D16 (SCR efficiency) and 452A (DPF lifetime) codes.

452A does not cause MIL
4D16 trips MIL and returns within 500-700 mi of clearing.

Question is:

Do I clean CBU in hopes of improving combustion and clearing the efficiency code or do I need to bite the bullet and get a new DPF and SCR cat?

Also interested in hearing DPF cleaning experiences, ive spoken to two cleaning outfits who say the BMW DPF has an additional OX CAT in the DPF that must be removed prior to cleaning and reinstalled (cut open and weld closed DPF)


HELP, im only a few months away from my SMOG inspection ... I will not pass in the current state.

Please refrain from telling me to delete the car, I am well aware of the pros and cons of these modifications I wish to remain compliant with CA SMOG laws at this time.

[peteyypab]

Additional Information:

• ISTA test plan indicates to replace SCR and DPF.
• New thermostat, runs consistent 87-88, I’ve seen as high as 99 (assuming regen)
• New nox sensors under cpo - need to check mileage @ replacement ( before 100k)
• New def heater (temp sensor failure)
• New def injector (thought I broke old during cleaning in attempt to chase 4d16 code, no change)

[335dlci]

You can try cleaning it. It's helps on a few clients vehicles. The 4d16 could be a number of things. Clearing faults does not fix the issue btw.

[peteyypab]

Originally Posted by 335dlci

You can try cleaning it. It's helps on a few clients vehicles. The 4d16 could be a number of things. Clearing faults does not fix the issue btw.

Thanks, was hoping some of the experts would chime in

In your experience could 4d16 be caused by CBU alone ?
Could 4d16 be caused by a "spent" DPF/OX CAT?

I gave the code clearing information to give you a picture of frequency, from my understanding 4d16 is tripped after 2 “inefficient” regens? - This metric has changed, was throwing it much more frequently until thermostat replacement.

I’m aware there is a problem and just want to apply the correct fix without shooting the parts cannon aimlessly.

[335dlci]

Originally Posted by peteyypab

Thanks, was hoping some of the experts would chime in

In your experience could 4d16 be caused by CBU alone ?
Could 4d16 be caused by a "spent" DPF/OX CAT?

I gave the code clearing information to give you a picture of frequency, from my understanding 4d16 is tripped after 2 “inefficient” regens? - This metric has changed, was throwing it much more frequently until thermostat replacement.

I’m aware there is a problem and just want to apply the correct fix without shooting the parts cannon aimlessly.

It honestly depends on the upkeep of the rest of tje vehicle.

[peteyypab]

Originally Posted by 335dlci

It honestly depends on the upkeep of the rest of tje vehicle.

Besides CBU, everything has been over maintained (early oil changes, filters, ALL vacuum lines,etc) just never had any cbu related or injector codes

Interestingly enough I hit the low def level (999 no start) and refilled with 2.5 gallons supertech DEF in the passive tank, all monitors are ready and it’s been ~600 miles Here’s to hoping it was just poor quality Peak DEF

[awenthol]

How mechanical are you? You can pop the intake manifold off and inspect the ports. Also, where are you located/what kind of climate are you in? CBU is going to be exaggerated in cold climates.

If you're not getting enough fresh air, it can cause regen issues, but the ECM will also see this with MAF readings, and you should see faults there.

[335dlci]

If you're in socal. I can help.

[335D Alpha Pappa]

The dpf meter can be reset. It expires around 160k miles. Its a hard countdown clock. The foxwell scan tool can reset it. As long as the dpf isn't clogged it should be good to go for a while.

I've had the 4D16 code a couple of times. I have pulled the rear nox sensor off and spayed it with brake clean to remove the soot build up. Ive cleaned it at 130k and 200k but I've just replaced the nox sensor after the 3rd time. The brake clean didn't work well so I replaced it.

Make sure your scr temp is at the correct temp. If not then it has to be replaced.

When you erase error codes, it resets the I/M monitors and the SES light comes back after about 500 miles or after the car has run a full tank of fuel because the scr and dpf monitors are the last to reset. So the SES light stays off until those monitors reset and if the code is active the light will come on. If the errors are not active but in history the SES light will turn off after a 3 or 4 drive cycles.
In my state to pass vehicle inspection, only 2 monitors can be incomplete, all others must be ready.

[peteyypab]

Update time:

its been a few months, 178K now and counting... no changes made BUT:

• Cleared the DPF lifetime counter.
• Still getting intermittent 4D16 code
• DEF active tank Temp sensor failed (AGAIN) new heater pot on order.

Im thinking I either have a flaky/wonky NOX sensor or something is affecting my DEnoX process or my SCR is just not meeting the threshold for 4d16 code set criteria.

I have concluded my SCR/DPF is working at least to some degree... When I clear codes I can get through several tanks of fuel (including a regen) and get all I/M readiness monitors passed with no pending codes. continue driving anywhere from 800-1500 miles and BAM 4d16.

Passed Smog but would like to get this cleared up and maybe get a few MPG back in the process??

[Scubudo]

I don't think that regular preventive maintenance will prevent the need for a carbon cleaning...but an EGR block off/delete will.

[lnxguy]

Don't drive it like a 90 year old lady, you'll be good. EGR block/delete or not you're still ingesting oil from the CCV.

[peteyypab]

Both NOX Sensors replaced by dealer in 2017 at 97k, thus my current sensors are 6 years old with 80k on em.

Could it be that the NOX Sensors are just lazy but not throwing a code?? I would like to think you would get plausibilty or out of range codes with a failing sensor and not just the 4d16

Anyone have some known good NOX sensors for some testing?

[335dlci]

Apparently you don't know that scr isn't fully "ok" until hundreds of miles if the correct drive cycles haven't been done correctly

[335dlci]

Originally Posted by peteyypab

Thanks, was hoping some of the experts would chime in

In your experience could 4d16 be caused by CBU alone ?
Could 4d16 be caused by a "spent" DPF/OX CAT?

I gave the code clearing information to give you a picture of frequency, from my understanding 4d16 is tripped after 2 “inefficient” regens? - This metric has changed, was throwing it much more frequently until thermostat replacement.

I’m aware there is a problem and just want to apply the correct fix without shooting the parts cannon aimlessly.

Actually your comment is funny because I am an expert but I'm not here just to hand out all my experience for free. Therr are bulletins for this fault but hey you're the expert

[335dlci]

Originally Posted by peteyypab

Update time:

its been a few months, 178K now and counting... no changes made BUT:

• Cleared the DPF lifetime counter.
• Still getting intermittent 4D16 code
• DEF active tank Temp sensor failed (AGAIN) new heater pot on order.

Im thinking I either have a flaky/wonky NOX sensor or something is affecting my DEnoX process or my SCR is just not meeting the threshold for 4d16 code set criteria.

I have concluded my SCR/DPF is working at least to some degree... When I clear codes I can get through several tanks of fuel (including a regen) and get all I/M readiness monitors passed with no pending codes. continue driving anywhere from 800-1500 miles and BAM 4d16.

Passed Smog but would like to get this cleared up and maybe get a few MPG back in the process??

also the scr and dpf are NOT the same system so they will trigger faults differently

[torqueisking]

Did the ISTA test plan indicate replacement of the DPF due to mileage, codes or "Intake Port Sooting" result?

[Scubudo]

I am no expert, but it isn't very difficult to pull your intake manifold off to look.
If you see anything that looks like this picture, I can't imagine how any type of driving will clean this mess up.

[nonford]

If its a highway vehicle, with no to very little idle city traffic, then I can see no carbon build up. I have 108K on mine and never seen what other posters have shared images of their cbu. I drive mostly highway and the ports are pretty clean!!!!