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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8870
Experience:  I am ASE Master Truck Certified.
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Why will my 2008 peterbilt NOT perform a parked regen? The

Customer Question

Why will my 2008 peterbilt NOT perform a parked regen? The dpf indicator is flashing and the dash msg says regen required. Maint on truck is performed monthly and it does a passive, enhanced passive and computer initiated regens just fine. It has a 3 position dash switch which is set to center position. The software is up to date. No one can seem to figure it out. Any ideas?
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 year ago.

Thanks for asking your question. I will try and help you out.

So the regen light will come on but will not perform a manual regen, but will complete one while driving? Is that correct?

Customer: replied 1 year ago.
that is correct
Expert:  Cat Man replied 1 year ago.

Thanks for the information.

Unfortunately I have seen this many times. I would suspect the engine EC is detecting the clutch switch being pushed, or the brake pedal not pushed, or the accelerator pedal not at idle. If one of these are happening, the engine will not perform a parked manual regen. I would have these read with Cat ET while running to verify.

Also, Here is a regen card that you should find very helpful.

Please reply back if you need more help, I am happy to assist.

Customer: replied 1 year ago.
I think the issue has to deeper than what you are alluding to. Wouldn't the fact that a computer initiated regen can be completed successfully mimic or require the same conditions that you are indicating have to be met (i.e. No clutch, brake or accelerator activity for a parked regen? The ET computer has shown each time in the past that the truck is reading well within all parameters. Any other ideas? I am coming for your insight as this has been looked at by many cat certified techs and no one has been able to ascertain any specific problems. Most of the obvious items have been reviewed and checked st this point. This is not a new or recent issue. It has been with me for quite some time.
Expert:  Cat Man replied 1 year ago.

I see. Thanks for the information.

A computer initiated regen will override any switch position issue. This will only happen when ET and a forced regen.

If the brake clutch and accelerator are not causing the system not to regen. I would next look at the pending checks before the regen. The pending checks are:

Secondary air gas mass flow must be within 150-220 ib/hr

Fuel pressure control command must be between 50-80%

CGi mass air flow must be below 500.

If any of these are not met, the system will not initiate a regen with the manual switch. If these are all within specs, there is only one other thing that can cause a manual regen not to start. That is the ECM is detecting too much load on the engine. If the ECM thinks its under load and a parked regen is wanted, it will just not start a regen. IT detects load by fuel pulse commands to the injectors. If the pulse command is too high, it will not do a parked regen. The only thing I have seen take care of this problem is to relieve a known load on the engine. PTO, Air compressor, fan, etc. I like to verify this by removing the fan belt and removing the load from the engine. if it does a regen. Youll know its detecting too much load.

Now, this does not mean these items are necessarily bad. It normally means the injectors are worn and the ECM needs to extend the pulse command to hold the engine speed. The ECM thinks the engine is under load a will not start a regen. Ling story short. Worn injectors can cause your problem. I am sorry. I wish I had better news.

Please reply back if you need more help or have more questions. I am happy assist.

Expert:  Cat Man replied 1 year ago.

Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.

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