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Ask Allisonforeman Your Own Question
Allisonforeman, Transmission foreman
Category: Heavy Equipment
Satisfied Customers: 300
Experience:  Factory trained by Allison Transmission on all on Hwy products including the Hybrid Electric drive,
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Freightliner..lose power..a diagnostic and the following codes..boost

Customer Question

I have a 2005 freightliner with a 60 series Detroit engine. I been having the following problem, when I am on hauling a heavy loads I sometimes lose power and can't go any faster than 50 miles an hour, and all of a sudden my truck gets a surge of power and works normal for a while and the problem re-occurs. I have taken it for a diagnostic and the following codes came out VNT vanes not responding -boost jake & VNT vanes not responding -boost power. Any suggestions?
Submitted: 7 years ago.
Category: Heavy Equipment
Expert:  Allisonforeman replied 7 years ago.
Hello and thanks for using Just Answer from your description the VNT is malfunctioning causing a low boost condition. 2 things could normally cause this, one of the V-pods could be malfunctioning or the VNT could itself be bad. I would suggest taking the truck to a Detroit dealer who can use diagnostic equipment to determine which is causing your concern. The V pods would be the cheaper of the two repairs, repairing the VNT requires complete turbo replacement.

I hope this info helps
Customer: replied 7 years ago.
Would it cause any Engine problem if I continue to run the truck like this? Because like I said sometimes it works fine, and sometimes I just loose power.
Customer: replied 7 years ago.
I took your opinion and took it to a shop and again it was VNT not responding, but I also got a new code, 29 which is TCI temo failed and 51 temo failed high and TCI temp above range which is 49, but they told me it had nothing to do it with flash 39. Is that true? I am just trying to not get srewed over at the shop.
Expert:  Allisonforeman replied 7 years ago.
The VNT codes should be addressed, whenever engine power has been affected, other codes can also be set. Have the shop address the VNT concern first,it is a very common concern at our shop.

Customer: replied 7 years ago.
They are currenlty addresing that, but do codes 49, 51, & 29 have anything to do with my turbo not working properly? Are they somehow connected?
Expert:  Allisonforeman replied 7 years ago.
I cant say for for 51 and 49, I am away from the shop, but code 29 relates to the Turbo compressor inlet or outlet temp signal voltage being out of spec,so yes 29 would be related to your turbo.

Customer: replied 7 years ago.
Ok Bill and my final question is would flash code 29 trigger the VNT to malfunction causing flash code 39 VNT not responding to also flash? My understading is that flash code 29 is a sensor right? So if the sensor is not working at all, would it affect the VTN is a way that flash code 39 come us?
Expert:  Allisonforeman replied 7 years ago.
I would say no the 29 would not cause a 39. The 29 is caused when the signal voltage drops below a certain value from either the turbo compressor inlet or outlet temp sensor. So you cant rule out a harness problem either, this is why using a Detroit dealer with properly trained personnel is so important.
Allisonforeman and 2 other Heavy Equipment Specialists are ready to help you
Customer: replied 7 years ago.
k thanks alot Bill.
Expert:  Allisonforeman replied 7 years ago.
You got it, No problem.