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Robert R
Robert R, ASE Certified Master
Category: Dodge
Satisfied Customers: 3928
Experience:  Dodge Master Certified, Dodge Sprinter Certified
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My diesel 6.7 truck cycles off and on when it warms up

Customer Question

my diesel 6.7 truck cycles off and on when it warms up almost as if the power was flickering off and on
Submitted: 2 months ago.
Category: Dodge
Expert:  Robert R replied 2 months ago.

Hello, welcome and thanks for asking your question. My name is*****'m a Certified Auto Technician with 29+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern.

Is this an idle fluctuation up and down?

Customer: replied 2 months ago.
No it happens on idle to some extent but it stalls Un less I throthe it than it cycles a lot more
Expert:  Robert R replied 2 months ago.

You said it had a code for turbo speed sensor. What was the actual "P Code" that is being set?

From your explanation, it sounds like you may have a stuck turbocharger or a plugged DPF.

What do you do to get the problem to go away? Does it go away after the engine has warmed up?

Customer: replied 2 months ago.
2579 is the code I got which indicated that the turbo speed sensor is acting up I replaced it to no avail also checked old sensor it checked out ok. the input voltage of about 2.5v going to sensor have not found out if this is ok maybe you can enlighten me on this. the problem becomes apparent when the motor warms up.
Expert:  Robert R replied 2 months ago.

Ok, there are a couple other possibilities for the P2579 other than the Turbo Speed sensor. I'm posting the diagnostic procedures for this code. if you need additional info don't hesitate to ask..

P2579 Diagnostic procedure --->> Click Here to view <<---

Run the diagnostic procedure and post back the results..

Thank you,

Robert

Customer: replied 2 months ago.
would this possibly cause the engine to cycle?
Expert:  Robert R replied 2 months ago.

The most common causes for engine to be cycling is a plugged DPF (Exhaust Filter) or a Stuck Turbocharger Sliding Nozzle. Usually you would have other codes such as p1451 and p242f and also p2262 or p2563.

At this time I recommend to diagnose for the code that is coming up and get this code to stay cleared and it should solve your problem...

Keep me posted and let me know if you have any additional questions...

Thank you,

Robert

Customer: replied 2 months ago.
no those codes did not come up only 2579 and 2580
Expert:  Robert R replied 2 months ago.

A sticking sliding nozzle in the turbo could cause these codes depending on what position the nozzle is sticking at. When it sticks closed, it usually limits engine rpm as the engine is having a hard time expelling the exhaust gasses. This causes the idle cycling or fluctuation and limited max rpm and possible smoke depending on the condition of the DPF. Most likely you will end up needing to replace the complete turbocharger assembly...

Keep me posted and let me know if you have any additional questions...

Thank you,

Robert

Customer: replied 2 months ago.
just checking 1 more time what is the voltage going to the speed sensor I presently have 2.44 volts is that correct? I have been told it should be 5v have not been able to confirm.
Expert:  Robert R replied 2 months ago.

The Turbo Speed Sensor generates it's own signal --->> Click Here to view <<--- Because of this, there probably should not be any voltage present on the Turbo Speed Sensor wires. There is no published info as to if there should be voltage present. See the diagnostic procedure I posted above for the Proper testing procedure. It never has you checking voltage it just has you testing the sensor itself and checking the wires, If all that is ok then the ECM is assumed faulty and will need to be replaced....

Keep me posted and let me know if you have any additional questions...

Thank you,

Robert

Expert:  Robert R replied 2 months ago.

Best thing to do would be to disconnect the sensor and the ECM C1 connector and check if voltage is still present, If there is, Further testing will be required to see where the short to voltage is at. Otherwise, test the wires per the test procedure above and you should be able to easily narrow down the culprit....

Keep me posted...

Thank you,

Robert

Expert:  Robert R replied 2 months ago.

Another possibility per the possibilities section in the flowchart is the Boost Pressure Sensor (AKA MAP Sensor). Unfortunately, the diagnostic procedure never leads to this sensor as a result so you may find that just replacing the Boost Pressure Sensor may fix this issue...

Keep me posted and let me know if you have any additional questions...

Thank you,

Robert

Expert:  Robert R replied 2 months ago.

Here is the P2580 Chart, it may help for diagnostic purposes..

--->> Click Here to view <<---

I found a star case for this code also

--->> Click Here to view <<---

Thank you,

Robert

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