Over boost while jaking

[Northern guy]

I have a Isx 2250 that is a drop in 4500hrs ago warranty is done was de mandated a year a go and has run flawlessly. Happy with the results with it. A few months ago I developed issues with the vgt actuator it had defeated and coded out just with the service indicator not stop engine. I took it into my local Cummins shop for repair got it fixed. Was gone about a hour and brought it back with a stop engine light. What’s looked at again and decided that the vgt actuator was faulty. Changed it and went back to work. A few hours later I was back again with codes on the turbo and now the engine is over boosting while jaking and not performing as it should on the jakes settings it over boosts while on the third stage up to48 psi at times, then will blow the boost back out the air cleaners when you touch the throttle. Back at the shop they recalibrated the vgt actuator and inspected the turbo. The vains move freely. Back to work. Well back into the shop as of stop engine light again. More diagnostic on engine changed all the sensors that may have or have not needed to be changed and problem still remains but with no engine codes. So the shop has a test turbo that they tried and didn’t solve the problem. So replaced it with my turbo. Then took off the new actuator and put my old one back on and doing the same as the new one. Now with out any codes as when I brought it in. Now they try a test ecm that they have with the same programming
still reacting the same way over boosting while jaking. Now afterwards my ecm is back on and it is still the same. This is all done over a space of 3 weeks as they are out of ideas. And the the say they are out of ideas on what to do. Basically come and get your truck out of out yard.
Seams to me one the jaking issue to me is it doesn’t like high rpm jaking works better when starting at a lower rpm and ramping it up. Seams like when jaking it Down to mid range rpm it wants to vibrate a little. I’m thinking that it’s the vgt not knowing where the chains are supposed be set at and are fluttering. The engine runs flawlessly otherwise. Boost is where it’s supposed to be while pulling. Any ideas out there ? Out of patience and don’t want to run it till a major issue shows up but may have to.

[Mr Hagg]

Sounds to me you are having data link issues. Need to ohm the harness to acuator should be 60 ohms plugged in and 12volts. What we find is there is a issue on the def tank and that carrys the same data link as turbo. So what we do is find terminal resistor and relocate it to the same harness as turbo

[Northern guy]

Thanks for your reply and will look into this

[Wildcard]

A cummins shop had a test ecm with the same programming as your deman'd 2250?

[Northern guy]

Yes. They had one from a engine that had a rod let go on and bought the remains from the customer

[tree98]

(02-22-2023 )Northern guy Wrote:  Yes. They had one from a engine that had a rod let go on and bought the remains from the customer

Sounds like a great tune......... You would be wise to have that program checked by Rawze before your engine does the same.

[trucklogger2]

(02-21-2023 )Northern guy Wrote:  Thanks for your reply and will look into this

After that you may want to give the backpressure sensor and supply tube a look into.
Try a new one and blow out tube.(pipe)

[Rawze]

BAD DELETE programming is a plague in the trucking industry .. and almost all truck owners will swear the truck "runs great otherwise".. until just like the blown engine in that shop .. a piston goes thru the block, or it takes out a turbo or 3 .. and other horrible things set in, due to someone 's garbage-delete-programming incompetence.

Eliminate the most obvious thing (possible bad delete programming that has a high chance of being unstable) that your post implies FIRST.. and not last.. and then you can go from there.

I don't care how well you think it might run otherwise, most truck owners would swear their delete "runs great" .. all the way tot he day it blows the had gasket..or till that turbo blows up.. or far worse.. puts that piston right thru the side of the engine block!.

It "seeming to run ok" is exactly WHY the trucking industry is so badly plagued with bad delete programming that is not worth putting in a lawn-mower, nonetheless a $40,000 commercial engine.

Do the other things suggested on the forum here so far, BUT ALSO START BY assuming that program very well might be total garbage, having a heavy chance (90% chance by statistics) that it could be significantly harmful .. and quite frankly.. the root cause of your issues.

Copying the program out of that ecm (using the Calterm software) and e-mail it to me for a proper review to ensure you are not chasing something that some moron might have created in that ecm at some point.


Make sure you boost gauge is reading correctly.. 48-psi is a pretty high number there...

48-psi either on boost or during jake.. CAN AND WILL DESTROY THAT ENGINE WITH ABSOLUTELY ZERO WARNING!. Boost should never ever be above about 36 psi on that engine.. no matter what the HP/torque rating.. and jake should roughly be cresting at about 28 psi or so max.

[Josiah Harder]

(02-22-2023 )Rawze Wrote:  BAD DELETE programming is a plague in the trucking industry .. and almost all truck owners will swear the truck "runs great otherwise".. until just like the blown engine in that shop .. a piston goes thru the block, or it takes out a turbo or 3 .. and other horrible things set in, due to someone 's garbage-delete-programming incompetence.

Eliminate the most obvious thing (possible bad delete programming that has a high chance of being unstable) that your post implies FIRST.. and not last.. and then you can go from there.

I don't care how well you think it might run otherwise, most truck owners would swear their delete "runs great" .. all the way tot he day it blows the had gasket..or till that turbo blows up.. or far worse.. puts that piston right thru the side of the engine block!.

It "seeming to run ok" is exactly WHY the trucking industry is so badly plagued with bad delete programming that is not worth putting in a lawn-mower, nonetheless a $40,000 commercial engine.

Do the other things suggested on the forum here so far, BUT ALSO START BY assuming that program very well might be total garbage, having a heavy chance (90% chance by statistics) that it could be significantly harmful .. and quite frankly.. the root cause of your issues.

Copying the program out of that ecm (using the Calterm software) and e-mail it to me for a proper review to ensure you are not chasing something that some moron might have created in that ecm at some point.


Make sure you boost gauge is reading correctly.. 48-psi is a pretty high number there...

48-psi either on boost or during jake.. CAN AND WILL DESTROY THAT ENGINE WITH ABSOLUTELY ZERO WARNING!. Boost should never ever be above about 36 psi on that engine.. no matter what the HP/torque rating.. and jake should roughly be cresting at about 28 psi or so max.

Hey Rawze I was just reading through this and am now worried my X15 might be over boosting while jaking too. Mine is not de mandated but since I last had trouble with the truck not running due to what Peterbilt diagnosed as high exhaust back pressure because of the actuator being stuck I have been getting 38-40 psi of boost on 3rd setting Jake. I cant say for sure it was not always that high because I don't remember what it was normally at but my 2nd setting is consistently 20-22 but my 3rd setting almost seemed too high to me and now reading your cautionary comments about boost not exceeding 36 I'm worried. Unless my engine is different and that is normal but I don't want to blow anything up like you warned of so I might just avoid using the 3rd level. Also will my gross weight and level of grade effect how much boost is created when Jake breaks are on?