Archived Cat. converter/dpf breakdown

[asptsman]

Towing my fiver through Vicksburg, Ms and got engine light and reduced power. No other warnings. Dodge dealer says cat. converter doesn't get hot enough to fire-up the dpf????? This is the second time dpf has failed. Last time was in Alabama last Dec. in very cold (15 degrees) weather. Replaced dpf then. Now waiting until Tuesday to get cat. converter and new dpf shipped in. Anyone had this problem or any ideas why it happened? Heading out on another big trip next week if truck gets fixed. Not a happy Dodge Owner at this point







2007. 5 3500, SRW, completely stock, towing 12,000# Montana

 

[HBarlow]

I'm not saying that the dealer's diagnosis is incorrect but have never heard of the situation you described. It doesn't make sense to me but I'm not a mechanic.

My advice would be to read the codes and post the codes here. We have at least three Dodge dealership techs among TDR members and lots of other TDR members who are knowledgeable and skilled mechanics who can interpret the trouble codes and offer good advice.

Do you know how to read your codes? Start with engine Off, truck in park, ignition OFF. Rotate key switch from OFF to ON, ON to OFF two times quickly then from OFF to ON and stop. Any trouble fault codes read by the ECM should be displayed in the odometer. Read and record the codes that appear and return to TDR and post them.

Do you have any magic black boxes or other engine modifications?

Another alternative is visit an Autozone or other chain autoparts store. They have a scanner that can plug in under the steering column and read codes.

 

[asptsman]

HB,

Thanks, but the truck is at the dealers until the Holiday is over and I can't get to it. I'll pull the codes on Tuesday. No engine mods. Been trying to stay under warranty after the episode last December. In the post I forgot to show the milage which is 67,000.

Asptsman

 

[MChrist]

It's my understanding that the converter heat has nothing to do with the DPF function. Also, I read that the converter on diesels "lights off" at around 400 degrees.
As a side note, since my truck runs very cool EGTs and I still have my converter intact, I wrapped the down pipe with high temp header wrap all the way to where the pipe expands for the converter. That was my attempt at keeping the hot gasses hot until it gets to the converter. I haven't noticed any problems, as my truck runs like a scalded ape!

 

[Bob4x4]

Dpf failure is very rare. Many have been replaced that didn't need it. If they are severy overheated they can crack at that point they do not capture the soot and you will have the old style soot in the tail pipe

 

[HBarlow]

Aptsman,

My advice is go to the dealer first thing early Tuesday morning and ask the service advisor to give you the list of fault codes the tech read from your ECM and show you the diagnostic information he should have downloaded from the MOPAR computer system. Normally I think the tech has to read codes on his scanner and the computer prints out a diagnosis or more than one suggestion to narrow the fault to one. I'm fairly certain they can't replace anything under warranty now without performing some variation of what I just wrote. If you are paying he can replace whatever you are willing to pay for.

If the service writer is not helpful be warned. If he cannot or will not provide them take your wife's spare key and go sit in your own truck and read the codes. Tell the service advisor you need to retrieve something from your truck to gain access if you need to avoid appearing to challenge them.

I'm not sure what is covered under warranty and what is not. The Cummins engine and all internal parts is warranted for five years 100k miles. I don't know whether catalytic converters and/or DPFs are covered at 67k miles.

A DPF costs around $2500 or more installed at a dealership. A cat converter is not cheap either.

Don't be down on your truck. Most of us enjoy many years and hundreds of thousands of miles of troublefree service from our Cummins powered Rams. The late model trucks are complex and many dealerships are simply not staying current with the technology.

Don't authorize repairs until you have the opportunity to run the codes and symptoms by the dealer techs and other knowledgeable owners here in TDR.

 

[HHhuntitall]

I'm gonna have to agree with HBarlow, here. I'm not a current Ram tech, but I work on a lot of trucks, including Class 8 trucks, and I fully understand it's principles of operation and functions. On that note, I've seen a lot of problems with the DPFs, but not the cats..... especially with so few miles... . very few times have either had to be replaced, as typically it lies with an electronic failure, which is remedied with a current flash or sensor replacement... . I'd be highly suspicious of a dealer that wanted to replace it twice. I can see how the cat might not function properly in extremely cold ambient temps, which would require the DPF be replaced, as the Cat is supposed to elevate Exhaust Gas Temperatures high enough during regeneration to burn off Diesel Particulates (soot) accumulated in the DPF (Diesel Particulate Filter) and Nitrides of Oxygen trap... . but not while towing a fifth wheel trailer. But in either case, I wouldn't think the cat would have to replaced, unless you've gotten it exceedingly hot, which could have "burned out" the convertor's reactant core..... but not with the low mileage you indicate..... I'm curious as how this is going to turn out. I'm gonna say at this point, it will happen again, as the cat's not the problem and they're treating symptoms... ... unless you're just driving your truck harder than any hotshotter I've ever seen..... Please gather a little more information and pass it on to us, please...

 

[asptsman]

HHhuntitall,

Just the opposite. I am pretty soft on the truck. Have installed EGT temp guage and transmission guage and watch the temps all of the time. Will try to get the codes and post them tomorrow. Dealer is doing everything under warranty so it can't hurt to have the new items installed. I just don't want to get left on the side of the road again.

 

[AH64ID]

Hopefully they get it fixed up for you.

Have an EGT (I presume that's what you means) gauge on a bone stock 6. 7 is kinda a double edged sword. . You really can't hurt the stock motor, and if you drive to keep the EGT's down you are hurting the regeneration process. Regen will take the EGT's well above what was once considered normal on a diesel.

 

[Hoefler]

Hopefully they get it fixed up for you.



Have an EGT (I presume that's what you means) gauge on a bone stock 6. 7 is kinda a double edged sword. . You really can't hurt the stock motor, and if you drive to keep the EGT's down you are hurting the regeneration process. Regen will take the EGT's well above what was once considered normal on a diesel.

Totally agree. You can also run these engines too soft. Not letting the exhaust system get hot enough is bad. EGT will exceed 1450* while in regeneration. If you don't let it stay there, you are killing the system your self. Don't drive like you are on ice all the time. Drive it, believe it or not, your fuel mileage will be better when it isn't trying to regenerate every time you drive it. It will regenerate less when the exhaust has a chance to stay hot. I had gauges in my 08, I rarely saw it regenerate. I tow 95% of the time, whether it is a 16' loaded enclosed trailer ( about 6,500 lbs ) or my 40' fifth wheel ( around 15,000 ). The only time I usually seen a regeneration, was when I was tooling around in the city, it would regenerate shortly after. On a 3,000-4,000 mile trip, I wouldn't see but one or two regens in that period if any at all.

 

[HHhuntitall]

HHhuntitall,

Just the opposite. I am pretty soft on the truck. Have installed EGR temp guage and transmission guage and watch the temps all of the time. Will try to get the codes and post them tomorrow. Dealer is doing everything under warranty so it can't hurt to have the new items installed. I just don't want to get left on the side of the road again.

Well, if it's under warranty, I suppose you're ok. My concern would be thay are not fixing the real problem, which, maybe the last dealer didn't do, and this dealer will get it right. I'd hate for anyone to be stuck on the side of the road. Still, if you're towing a trailer, and are maintaining mph while traveling down the highway at the speed limit, you should have more than adequate EGTs to operate the regeneration system, if it's operating correctly. :raised-eyebrow: Certainly pay attention to it, as I'm sure you will. They've got MOST of the bugs worked out on these things, if they'll just work on 'em and keep a good service tech who's concerned about the customer.

 

[asptsman]

Went this morning and got the trouble codes off of the truck. There are two codes.

P242F and P1451. As I understand it the first is "ash accumulation in the Particulate Filter" and the second is "dpf preformance problem". Don't know if this will help but if anyone has any ideas I would appreciate hearing them. Soggy weekend in Vicksburg but tropical storm Lee did not blow us away. Need to get back to Georgia.

 

[HBarlow]

I can't confirm or deny that those codes point to a full or defective DPF but that seems to be very low mileage for a DPF to become full. The only DPF failure I have read about on TDR was EBs which had 225k to 250k miles when it required replacement.

Have you used anything but ULSD fuel? The previous LSD fuel can accelerate soot build up in the DPF. Have you routinely used fuel additives?

 

[asptsman]

Harvey,

I have ony used ULSD fuel. Maybe the problem is the cat. converter. The tech said that he couldn't get the cat. hot enough to light off the dfp. What I don't understand is the process for starting the regeneration process. What fires it up? n talking with my brother in Ohio (2002/2500 owner) he said that as many as 10 of his farmer friends have had this same problem but it seems to be because of the cold weather up there. That could not have been my problem coming through Texas where the temps were hotter than you know where. However, if the cat. was malfunctioning and not getting hot that may have caused the problem.

Thanks for your help

 

[HBarlow]

Here is my oversimplified and perhaps simple-minded understanding of how it works:

The ECM monitors driving time, distance traveled, and duty cycle in mysterious ways and initiates the regeration cycle by causing each injector to inject a tiny quantity of fuel after the exhaust valve has closed (at the end of the fourth cycle of a four cycle engine). The extra shot of fuel is discharged down the exhaust stream and causes the oven (DPF) to light off and burn the accumulated soot particles converting them to ash.

The cat converter should certainly be hot enough when pulling a heavy fiver across the southern tier of states in this summer weather but the cat converter doesn't really play a major role in the regen process to my understanding.

You didn't answer the other part of my question. Have you used fuel additives?

Edit: Now that I read what I just wrote I'm not sure of my explanation. It doesn't make sense. My memory of what I've read or been told may be faulty. Perhaps the extra shot of fuel is injected at the end of the exhaust stroke but just before the exhaust valve closes.

 

[HHhuntitall]

IIRC, and I may not, most of the elevated temps in the Catalytic Convertor are achieved through fuel injection timing and variable turbo geometry. I don't remember there being a fuel injector cycle being actuated at the end of the exhaust stroke, but again, I may not remember correctly... . and I may remember another brand emission function. But regardless, most of the issues I've seen with the Cat and regen are attributed to programming malfunctions, and typically fixed with an ECM flash. The ECM reads the pyrometer temps, three in the exhaust system, IIRC, the two oxygen sensor readings, and the backpressure readings, pre and post DPF, as well as fuel consumption, ambient air temp, fueling rate, and a multitude of other parameters I'm probably forgetting, to initiate the elevated EGTs, which in turn elevates the Cat temp, which initiates regeneration in the DPF and oxides trap. IIRC, again, the DPF has to be fired at upwards of 1500* to begin burnoff... ... . We're lucky to have the Dodges... . these Class 8 trucks are having to have the DPFs cleaned anywhere from 40k to 120k miles. They spend more time in the shop than on the road. And now Cheby and Furd have Weasel **** additive, as do a lot of the newer agricultural tractors. Burning more to create less... . makes a lot of sense to me!!

 

[asptsman]

Harvey ,

Thanks. I have used an additive called "CRC" at the suggestion of the Dodge dealer that replaced the dpf the last time. However, I only put it in every 15,000 miles and it has been at least 3000/4000 since I used it last. prior to the last dpf going bad I had not used an additive. Think I'll stop using that.

 

[HBarlow]

I don't have any suggestions to offer. It does not make sense to me that an unmolested (unmodified) engine with only moderate miles accumulated, that has not been contaminated with bad fuel, wrong fuel, or fuel additives, which was towing a fifthwheel in hot weather would set a code for what appears to me to be a full DPF. The DPF normally has a service life greater than what you are reporting.

I have no confidence in what your tech is telling you - that the catalytic converter is not getting hot and causing the problem and also do not understand why you would have had a previous DPF replaced under warranty.

How often does the truck pull a trailer? What is it normally used for? Are you on a vacation trip but the truck is normally a daily driver with short trips and light loads?

Has ANYTHING been modified that you've forgotten to mention? Anything in the intake or exhaust system?

Are you stuck in Vicksburg waiting for a new cat converter and DPF to be shipped? I was hoping that Mike Mullenax, sag2, or Bob4x4 would read and respond to your post. All three are knowledgeable Dodge dealer techs.

 

[AH64ID]

The DPF catches soot produced by combustion. The soot plugs the DPF, and the ECM monitors the pressure at the entry and exit of the DPF and when the backpressure hits a certain level the ECM knows the DPF requires a regeneration. The ECM then uses a late injection event to superheat the EGT's and provide the heat necessary for regeneration. The late event occurs near the end of the powerstroke, or on the exhaust stroke. The fuel does not contribute to any power, just exhaust heat as the heat/fuel go right out the open exhaust valve. This is also the reason the 6. 7 is so hard on oil, the late injection event leaves a trace of unburnt fuel on the cylinder wall which the rings then scrape into the oil. This is an active regeneration. A passive regeneration is when your EGT's are high enough to clean out the DPF without the late injection event. This only occurs when towing/hauling heavy loads.

The cat honestly has nothing to do with "lighting" off the DPF, it's for a different part of the emissions process. The cat is a NOx scrubber, where the DPF deals with the soot particulate.

I would say to watch your EGT gauge after you get the truck back, but don't let it alter your driving. Just drive like you would if you didn't have it and watch how it works. You will soon learn when you are in regen and what EGT's are normal.

 

[asptsman]

AH64ID and Harvey,

Thanks guys. AH, thanks for the explanation. I'll use that on the tech tomorrow.

The truck is used mainly for long haul and towing (12,000#). I have a '06 c-6 ZR51 which does the around town and golf course trips. The little woman drives an Avalon. So the truck is on the road most of the time. I am on vacation amd the truck is usually used for that and hunting trips. I other words I am using the truck in a manner that should never cause a regen problem. No modifications to the drive train. Yes stuck in Vicksberg waiting on parts which are supposed to be here in the morning.