Frequent Regen Diagnostic Tip

[Keith Browning]

The most common cause of frequent regen is vehicle going on short drive cycles that are not allowing the regen to fully complete. To complete a regen can take 20-40 miles of driving depending on conditions. There are a few PIDs we can monitor to help determine if this is the concern. DIST_REGEN_REQ, DIST_REGEN_C and DPF_LOAD. The DIST_REGEN_REQ is last mileage that the PCM requested regen to occur. The DIST_REGEN_C is the last time that a regen was able to complete fully and DPF_LOAD is the current soot load of the DPF. If the DIST_REGEN_C is much higher than DIST_REGEN_REQ it indicates that the vehicle has been attempting to complete a regen but has not been able too. When in regen it will stop if the vehicle is shut off, put in park or idles for more then 5 minutes.

[Aaron]

If I may add to this, Keith:

 

I have been working with the hotline a little on my own truck, for a frequent regeneration concern.

 

I'm at about 27k miles, and I have no soot in my tailpipes, so I think the DPF is okay.

 

This is the info I provided, and this is the info I got back in return.

 

Description of vehicle concern:

 

I have a question regarding the regeneration characteristcs of my vehicle. For the last three days, the vehicle has regenerated each time I have driven it to work (about 23 MILES), and when it has stopped regeneration, it has not said "EXHAUST FILTER DRIVE COMPLETE" on the information center. The regeneration frequency concerns me, as well as the lack of the information message. I am wondering if there is any known concerns regarding frequent regeneration. I realize the temperature change will have some effect on this, however every day regenerating for 15-20 miles is a little excessive and getting a little hard on the wallet. I have no black smoke present and no soot in the tailpipe, leading me to believe the integrity of the DPF is acceptable. Any advice would be appreciated, thanks in advance.

 

 

 

Diagnostics performed:

 

No DTCs are present, no aftermarket components, maintenance up to date, any common concerns I have experienced (melted DPF pressure sensor, EGR improperly operating causing excessive wet stacking, excessive idle time) are not present. If the truck idles for longer than 60 seconds, I have the PTO sense enabled to bump the idle off an upfitter switch (running in to get a coffee, etc.). The truck does not see any excessive idle time, a brief warmup in the morning, and cooldown periods after extended high speed or high load driving.

 

 

 

DTC Codes:

 

None

 

 

 

Parts replaced:

 

None at this time.

 

 

 

Tech's question:

 

Please reference the "Description of vehicle concern" portion of this report.

 

 

 

Hotline response:

 

Aaron,

 

There have been several reports of abnormal regen on 6.4L equipped units received by the Technical Hotline. Some of these reports reflect actual faults with the vehicles and some are found to be characteristic. With complaints of this nature, especially those in which there are no DTCs or other symptoms, it is important to first try and confirm to the best of your ability that the concern is or is not abnormal.

 

As per TSB 09-18-15, regen frequency can occur every 100-600 miles and can last for 10-40 minutes. To determine whether or not this vehicle's regen frequency is or isn't abnormal, enter IDS Datalogger and check the Dist_Regen_C and Dist_Regen_Req PID values.

 

The Dist_Regen_C PID indicates the amount of vehicle miles accrued since the last regen completed. The Dist_Regen_Req PID indicates the amount of miles driven since the last regen was requested. This information can be used to confirm normal operation.

 

For example, if the Dist_Regen_C shows 300 miles and the Dist_Regen_Req reads 10 miles, this indicates that the last regen completed 300 miles ago, but 10 miles ago, the PCM initiated the next event. This would be considered normal. However, if Dist_Regen_C shows 30 miles, and Dist_Regen_Req shows 10 miles, the regen frequency would be considered abnormal.

 

If the regen frequency is confirmed abnormal, refer to Symptom Chart 15 in Section 3 of the PC/ED for diagnostic steps.

 

If at this point, further assistance is required, it would be best to contact the Technical Hotline by phone to discuss this matter with an engineer.

 

 

 

 

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Call Log:

 

Calls to hotline for this vehicle:

 

 

 

11/23/2009 12:29:00 PM - Tech said:

 

Tech is calling in with a customer complaint of frequent regen. The air filter is stock and this seems to be a new issue. The engine will also runs rough at approximately 1000-1200 rpms when using the stationary elevated idle control. No DTC's are noted at this time.

 

 

11/23/2009 12:29:00 PM - Hotline recommended:

 

It is recommended to refer to SSM 21076 as a faulty MAF can cause the condition as described. SFT at idle can be monitored to identify an injector that is overfueling. Cylinder contribution tests can be performed as outlined in TSB 08-16-7 as well to help identify issues with cylinder overfueling. Replace faulty MAF, and overfueling injectors as found and retest.

[Keith Browning]

For example, if the Dist_Regen_C shows 300 miles and the Dist_Regen_Req reads 10 miles, this indicates that the last regen completed 300 miles ago, but 10 miles ago, the PCM initiated the next event. This would be considered normal. However, if For example, if the Dist_Regen_C shows 300 miles and the Dist_Regen_Req reads 10 miles, this indicates that the last regen completed 300 miles ago, but 10 miles ago, the PCM initiated the next event. This would be considered normal. However, if Dist_Regen_C shows 30 miles, and Dist_Regen_Req shows 10 miles, the regen frequency would be considered abnormal. , the regen frequency would be considered abnormal.

 

The above statement is similar to a vehicle I am looking at now BUT I was told this is ABNORMAL since the vehicle message center shows "Cleaning Exhaust Filter" every day, sometimes twice. Read this carefully:

 

 

[*]Dist_Regen_C = 327 miles

[*]Dist_Regen_Req = 0.06 miles

[*]DPF_LOAD = Clean

 

Notice that the last regen was over 300 miles ago, the DPF is showing as clean yet the PCM is requesting regen. Since regeneration is disrupted before it completes the cycle it restarts regardless of the loading. While this truck does do some idling it is probably not the cause of the frequent regenerations nor is the actual DPF load state. I am thinking that a regen cycle has other requirements beyond loading such as temperature of the cat/filter at the time of regen and time at temperature. Otherwise I would have expected the DPF_LOAD PID showing Clear to be sufficient.

[Aaron]

I was told to compare my MAF pids on my truck to a known good unit (lot unit) and if mine is not similar, switch it for a new unit. Apparently they have been having some MAF issues causing frequent regenerations.

 

And nobody can give me a cut and dried list of "When this PID is this, it will trigger a regen event" and so forth. Kind of irritating.

[Keith Browning]

Nobody ever mentioned MAF but since you mention it there is this recent SSM:

 

Quote:

2904 - 2008-2010 F-SUPER DUTY - P2463 AND P246C CODES WILL NOT CLEAR

SOME 2008-2010 F-SUPER-DUTY MAY EXHIBIT DIAGNOSTIC TROUBLE CODES P2463(DPF RESTRICTION-SOOT ACCUMULATION) AND/OR P246C(DPF RESTRICTION- FORCED LIMITED POWER) THAT WILL NOT CLEAR USING IDS OR MAY RETURN WITHIN LESS THAN 100 MILES FOLLOWING REPLACEMENT OF THE DIESEL PARTICULATE FILTER(DPF). THIS CONCERN MAY BE DUE TO MAF SENSOR CONTAMINATION. VISUALLY INSPECT MAF SENSOR FOR DEBRIS (DIRT/OIL) AND FOREIGN OBJECTS. PERFORM MAF SENSOR PCED PIN POINT TEST J TO CONFIRM SENSOR FUNCTIONALITY. PERFORM PIN POINT TEST RB TO VALIDATE DPF FUNCTIONALITY. CONFIRM AIR FILTER, FILTER LID, PCV PORT AND ALL ATTACHING HARDWARE ARE CORRECTLY INSTALLED AND LATCHED. ENGINEERING INVESTIGATION IN PROGRESS. MONITOR OASIS FOR FUTURE UPDATES.

[Aaron]

That's the same as SSM 21076 on inford.com

 

Numbers are different for US/Can?

[rlchv70]

From my understanding, the ECU used the DPF pressure sensor in conjunction with the MAF sensor to determine how much soot load there is in the DPF. It actually estimates the amount of soot in the DPF.

[Keith Browning]

Nice to have your input on this and your statement coincides with that SSM I posted so it is conceivable that MAF concerns will affect regens.

 

Unfortunately I don't think a MAF concern would cause the PCM to request a regen on a non-loaded DPF... or could it? In this topic we have two examples of a frequent regen condition: Aaron's is a true frequent regen and mine is a regen that does not complete...

[Jim Warman]

What Kieth posted looks like the broadcast message...

 

Let's be real blunt about the "no mods" statement... ain't nobody looking over your shoulder....

 

I'm still not up to speed on everything the PCM looks at to determine a regen need.... and I see the 6.7 using this exact same technology....

[Keith Browning]

Jim that was actually part of a HotLine response and it is the first of it's kind of information I have seen regarding the topic so I thought it would be good too share. I am not up to speed on this engine either as I don't see too many other than oil changes and catastrophic engine failures... but I am learning.

[Aaron]

Let's be real blunt about the "no mods" statement... ain't nobody looking over your shoulder....

No mods on my truck, I eliminated the tuner awhile back.

[Fordracer]

I see now there is a symptom chart 15 in section 3 of the PCED that covers this.

[Aaron]

Yeah, I saw that the other day. It's also on the ticker that plays while you're on hold with the hotline (Hi Guys! )

[rlchv70]

Nice to have your input on this and your statement coincides with that SSM I posted so it is conceivable that MAF concerns will affect regens.

 

Unfortunately I don't think a MAF concern would cause the PCM to request a regen on a non-loaded DPF... or could it? In this topic we have two examples of a frequent regen condition: Aaron's is a true frequent regen and mine is a regen that does not complete...

Actually, I think it would. In order to understand if the DPF needs a regen, the ECU looks at the exhaust backpressure. However, this is a function of the amount of exhaust flow. The exhaust flow is proportional to MAF. A simplification is that it will regen when it reaches certain MAF/backpressure combinations.

 

If your MAF sensor is reading high, it will think it is flowing more air than it actually is. Therefore, with a higher flow rate at the same exhaust pressure, it will lead to more frequent regens.

[Keith Browning]

Originally Posted By: Keith Browning

Actually, I think it would. In order to understand if the DPF needs a regen, the ECU looks at the exhaust backpressure. However, this is a function of the amount of exhaust flow. The exhaust flow is proportional to MAF. A simplification is that it will regen when it reaches certain MAF/backpressure combinations.

If your MAF sensor is reading high, it will think it is flowing more air than it actually is. Therefore, with a higher flow rate at the same exhaust pressure, it will lead to more frequent regens.

Okay, makes sense - I wasn't looking at it that way. Perhaps there is more to the current MAF investigation to come. If this truck returns I will be looking at MAF a lot closer.

[Cetane]

Originally Posted By: rlchv70

Originally Posted By: Keith Browning

Actually, I think it would. In order to understand if the DPF needs a regen, the ECU looks at the exhaust backpressure. However, this is a function of the amount of exhaust flow. The exhaust flow is proportional to MAF. A simplification is that it will regen when it reaches certain MAF/backpressure combinations.

If your MAF sensor is reading high, it will think it is flowing more air than it actually is. Therefore, with a higher flow rate at the same exhaust pressure, it will lead to more frequent regens.

Okay, makes sense - I wasn't looking at it that way. Perhaps there is more to the current MAF investigation to come. If this truck returns I will be looking at MAF a lot closer.

Keith,

MAF absolutely has an effect on regen frequency. It not only is an input to exhaust volume but the gas exchange system as well. So if the MAF thinks you are flowing more air than you actually are it will increase the EGR rate until you meet requested amount. In most cases this will lead to more soot production.

 

That being said I dont think you are looking at a MAF concern(at least as the reason for frequent regen). If it were, the pid that says clean would say dirty/plugged/clogged/f'ed up whatever message it gives you guys. There are five separate "rules" for requesting regen, it doesnt sound like you are tripping the one for high soot loading.

[Keith Browning]

No, I don't think so because this particular truck always reads "Clean" in the PID. The truck is coming back. The customer made every effort to drive the vehicle long enough once the message reappeared, about 45 minutes. I will bet when it returns it will show well over 500 miles since the last regen has completed... and the loading PID will show clean.

 

I am going to get the HotLine more involved on this one and my FSE is going to be visiting us later this week on another vehicle maybe I can get his input as well.

[rlchv70]

 

Keith,

MAF absolutely has an effect on regen frequency. It not only is an input to exhaust volume but the gas exchange system as well. So if the MAF thinks you are flowing more air than you actually are it will increase the EGR rate until you meet requested amount. In most cases this will lead to more soot production.

 

That being said I dont think you are looking at a MAF concern(at least as the reason for frequent regen). If it were, the pid that says clean would say dirty/plugged/clogged/f'ed up whatever message it gives you guys. There are five separate "rules" for requesting regen, it doesnt sound like you are tripping the one for high soot loading.

The 6.4L EGR strategy does not use the MAF sensor. It uses the EBP sensor and MAP sensor to determine EGR flow rate.

[Cetane]

I guess I stand corrected then. Some releases did use MAF, maybe they were development only.

[robp823]

Thank god finally good topic on regen problems!

[Jim Warman]

And Friday, I got an 08 in.... the air filter was installed backwards and only one latch was clipped... The intake is full of caked on dust...

 

The CEL is on but I've been working with some other concerns and haven't scanned for DTCs yet.

 

None of the people that drive this truck has complained about frequent regens or fuel consumption (but this could have more to do with the drivers than the truck).

[Aaron]

Well at least the filter was in there.

 

It's the thought that counts, isn't it?

 

How's the MAF look? Sandy, I bet?

[Jim Warman]

The MAF is a slightly different design... you can't see the sensing elements even after you take it out of the duct. At this point, I'm tucking the dirty intake info into my memory bank and we'll have to see if there are any obvious concerns.

[Aaron]

Best of luck, good sir!

[robp823]

While were talking about regen a couple quick questions...On PTS if your taking the 6.4l web based training it says that passive or active regen will not affect engine performance...Is this true??Also does anyone have the tsb number for characteristics of regen???