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VGT actuator; Diagnostic Code 2636


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Went to take off for the fourth of July and got about 1 block and red stop engine light came on.  Turned around and went back to the bus barn.  Error code 2636 shows up which says Abnormal Update Rate to the Actuator---the data cable not sending to the ECM.  So check a few things then started up again--no light.  So took it out on hwy and light came on.  WEnt about a mile and light went out;  ran about 10 miles and still no light.  So I tdurned around and went back to the bus barn.  Had lunch then tdried it again.  Light came back on;  ran for about 10 minutes in place and light went out.  Tried again this morning and no light; but it came on after about 10 minutes then would blink off and on every so often.  I checked for loose connections from the actuator to the ECM but nada.  Not sure what is going on;  several suggestions in the Cummins manual but have not gotten any further into it.  It appears that it is an intermittent thing--not sure if it is the 12V to the actuator or the data link.  Anybody have suggestions??   

Bob L, 08 dynasty.  P. S. bus has run perfect until this happened.  It only sat for about 2 weeks before I tried to take off for the 4th.       

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Posted (edited)

Sounds like you have a 07-08 engine with a complicated VGT activator… good luck with finding an intermittent problem.

Were you able to get 100% power with the light on?

I currently have a stuck VGT limiting how much boost I can get now that I’m out West. My 06 engine has an external activator that cannot be moved…thinking  of using oven cleaner in the exhaust side of the turbo to loosen the moving ring that varies the angle of the gains.

Edited by Ivylog
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This is the ISL;  07 engine and never has done this before.  Do not lose any boost with the red light on.  I started it this morning and it ran for about 10 minutes then the red light came on.  Tried to call Cummins in New Orleans but all I got was answer machine.  Left a message but have not heard back yet.  Oh and I have 75,000  miles on the coach.  It has been a great coach with no problems until now and I wish I knew how big of a problem this is cause I ran it on the hwy yesterday up to 75mph with no problem.

 

Bob L

Jim:  That is a possibility  Where are the resistors located on your coach;  I have an 08 dynasty

 

Bob L

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Jim:  That is a possibility  Where are the resistors located on your coach;  I have an 08 dynasty

 

Bob L

Thanks Jim:  Found them.  In same place as yours  Thanks,

 

Bob L

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Bobbyboy, hope this helps a bit.

The reason you see the light flashing light or the light comes on intermittently is likely a partially stuck actuator. It does it's job on the turbo when driving conditions demand it. No demand, no vgt function and no error light; intermittent light, intermittent demand. 

It is possible that the vgt actuator is not moving along it's entire range of motion and that is why you don't always see the error. The demand is satisfied within the current range of motion of the vgt sometimes and therefore an error is not always seen.

Here is a link to a YouTube video that may provide some more insight to Cummins vgt problems. This guy screwed up his initial vgt calibration when he worked on his turbocharger, but if yours hasn't been worked on you may simply have a partially stuck movement. Good luck.

https://www.google.com/search?q=vgt+actuator&oq=vgt+actuator&aqs=chrome..69i57j69i60l3.7231j0j4&client=ms-android-motorola-rev2&sourceid=chrome-mobile&ie=UTF-8#

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Bob, on your ISL the electronic turbo actuator communicates back and forth with the engine ECM.  The engine ECM will command a certain turbo position and the sensor inside the turbo will tell the engine ECM the actual turbo position . 

If you log into Cummins Quick Serve (no cost for this), you can look up the troubleshooting procedure to follow.  My hunch is a bad electrical connection on the electronic turbo actuator, a bad connection on the engine ECM or the turbo wiring harness was heat damaged due to incorrect routing around the turbo.

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Had a Cummin's tech look at it and after several different tests (resistance, etc) we concluded that actuator was shot.  Took it off and sure enough correct diagnosis.  Cummins has a new one coming in tomorrow.  The turbo looked fine;  the lever moved freely with no problem.  After we put it on and calibrate will post the final $$$.  I did have a mobile tech come out to my bus barn who really knows what he is doing.  

 

Bob L, 08 dynasty

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I had one diagnosed to be bad, and replaced in Salt Lake City by Cummins. They didn't connect the fuel lines properly and it slowly came undone over the next week and I had fuel spray all over the place, on the engine, on the tow, a little in the inside rear of RV, etc.

Cummins said it was not their fault and refused to cover the damage, repair, and tow.

Bad Cummins

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I'm curious why replacing a turbo actuator would cause a fuel leak.  We're you having other fuel related repairs done at the same time?

Electronic turbo actuators like on Bob's coach with an ISL engine are connected to oil and coolant.  Fuel connections are on the other side of the engine.

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Posted (edited)

My issue was the fuel accumulator (sorry about that, I got the term mixed up). When they disconnected the fuel lines to it they loosened the one below it when they tighten the one above it. So they tell me we didn’t do anything to that fuel line we only touched the one above it. That’s why they said it wasn’t their fault. In reality what happened was as the tech turned the open ended wrench on the fuel line going in to the actuator the wrench contacted the nut on the line below it. As he rotated the nut to tighten the top fuel line the wrench contacted the bottom nut and rotated it in the opposite direction, which loosened it. The tech did not notice this and that’s what resulted in the fuel leak problem

Edited by Corkman
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