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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3380
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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I have a 2011 Freightliner Business Class M2 with a Cummins

Customer Question

I have a 2011 Freightliner Business Class M2 with a Cummins that has the engine protect light on & won't rev up over 1900 rpm. I get only one active DT Code #68 secondary turbo inlet pressure, Fault Mode Identifier: 0. I tried to clear with an OTC scan tool, but it won't clear with the engine running or not. What could cause this problem? It has only 26,891 miles.
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 2 years ago.

My name is ***** ***** I will assist you.

CLICK HERE is the fault sheet for that code you have. I will be honest and tell you that when I see that code, it is 99% the EGR not working properly and replacing the EGR has cleared it. With you not getting that code to clear, I would bet the EGR is jammed up.

If you want to go through the diagnostics, I will load all 3 for you.




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Customer: replied 2 years ago.
Jeremy, I already disassembled & cleaned the EGR valve. It was quite clogged but now it's free. Do the actuators go bad and can they be tested?
Expert:  Jeremy replied 2 years ago.

The EGR could still be bad though. That is what is frustrating with them. Once the get clogged up, they tend to go bad quickly. The little plubger in there will bypass and not allow the rod to move fully. I've seen it many times.

Yes, the actuators do go bad, but there are usually other symptoms when they do. The truck won't seem to have good power being one of them. Plus the exhaust temps go way up and the regen will act up. You will get a lot of regens and you tend to have to do a lot of forced or parked regens because it doesn't get the pressure up enough to perform right.

There was no mention of that so that is why I pointed towards the EGR since all you have is the code. The EGR is typically always the culrpit. Now if you have other issues, then sway towards the actuator.

Customer: replied 2 years ago.
I just put a new EGR valve on & it has the same code DTC 68 and it won't clear. The engine protect light is still on & all the wiring looks good.
Expert:  Jeremy replied 2 years ago.

I provided the steps for diagnosing above. Did you follow them as well?

Customer: replied 2 years ago.
no I did not because what you sent was for fault codes 2347, 692 & 691 dealing with turbo compressor oulet & inlet temperatures below or above normal, the active fault code I get on the scan tool is 68 Secondary Turbo Inlet Pressure, FMI: 0 data valid but above operational range
Expert:  Jeremy replied 2 years ago.

code 68 secondary turbo inlet pressure erratic, intermittent,or incorrect. This is the 1587 code for the ones I provided above, which are the J1939 codes. All three of those above are related to this code.

Check the intake boost temp sensor and is it is still acting up, then check the turbo actuator since the EGR is good. That is the only other 2 causes that this code can come from.. If the actuator itself is jammed (which you would have gotten a 27 code for and I don;t see one mentioned, then most likey the turbo side is good, but the electronic side is acting up and not rotating fully meaning the actuator sent a code back to the ECM that it rotated, but the sensor is showing the turbo pressure isn't high enough or it's not moving fast enough.

That is the other 1% that causes the code. Nearly every ime i see it the EGR has caused the back pressure, the other 1% is the actuator itself causing the back pressure. I was hoping it was the actuator because it is easier to repair. The actuator will need Insite to program it off the truck and program it on the truck as well as coolant drained and fighting to get it off because of the location it sits on the M2. It's a pain to get behind the wheel well area to get it. It is only heal in with 4 10mm allen key bolts, but they break easy when at that weird angle to get it off to inspect it. Even when inspecting it you have to have Insite to calibrate it to put it back on.

Customer: replied 2 years ago.
when you mention that I will need Insite to program it off the truck are you refering to the turbo acuator?
Expert:  Jeremy replied 2 years ago.

Yes. The actuator has to have a "program" function done if it is replaced. If it is ever removed to even look at it, you have to do the "calibrate" function once it is mounted back on.

I will upload the steps so you will see what I am referring to.


VGT Video

Expert:  Jeremy replied 2 years ago.

If it is ever separated, the calibration must be done or you can have this code as well.