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Code 78

fonecop1

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The other day my SES came on right after pulling a long hill and stayed on till I got to work and shut it off. I cheched the codes lastnight and there was a 78 - Wastegate Solenoid code. I have been using a homemade mechanical boost controller for a year or so and few months back upgraded to an F chip and removed the vacuum pump. I thought it was strange to see the code 78 and thought that maybe it was an overboost because it happened after pulling that hill? If I push it going up a hill I do see pressures up to about 12 or so.
Thanks,
Bob
 
Sounds about right on overboost. Even if you have an "F" code PCM your truck is still set at the factory limit for boost control, which is IIRC, 12psi Chances are you overboosted. And since you have a mechanical boost cxontroller the truck cant control boost... but usually it will defuel as well to save itself. Guess you hit just high enough to overboost and throw a code, but not defuel perhaps
 
Need to keep it between 5 to slightly less than 8 with stock F PCM.

I have the T-master and have 78 everytime I go above 77 mph with 2.5 inch.
It goes to almost 9 psi.
 
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