Put new PCM/FSD.... now getting no turbo boost codes

[dually68]

I put external PCM/FSD module on...works great...but now I am getting turbo boost codes and truck has no power up hills or passing. What can I check or do....anyone? Dually68

[rjschoolcraft]

First, check the vacuum pump to see if it is making vacuum. Check ahead of the Wastegate Solenoid and after it. At idle, ahead of the solenoid, the vacuum should be around 25"Hg (IIRC, do a search on "vacuum", should turn up plenty of information). If no vacuum ahead of solenoid, check/replace the vacuum pump. After the solenoid, vacuum at idle should be about 15"Hg. If zero (or very low) after solenoid, replace the solenoid. If vacuum is good after solenoid, check the actuator on the turbo. At idle, you should not be able to open the wastgate by hand. If you can, something has failed in the actuator mechanism.

[dually68]

I checked the silenoid and the vaccuum checked out also. I cannot open the waste gate when truck is running either. The problem is I don't have a passing speed or the truck has less power after I get on the pedal. It feels like a gas burner bogging down.

[95C3500Cheyenne]

Are you getting a Code 75 or 72? I believe is Turbo Wastegate Solenoide. In my case the vacuum line had a tear/cut in it. Caused the wastegate to not operate correctly and would create a large amount of black smoke. Once repaired, the black smoke went away. and the truck no longer "bogged down" I also replaced the lift pump and fuel filter. Now the FSD is on the way out.

[patrick m.]

guages would be a big help here.
things to check: restriction in air filter/ or housing.
while the air intake duct is off the turbo, check for free rotation of compressor wheel (engine off of course)
check for intake gaskets leaks (almost unheard of)
check exhaust system for restriction.


as we are always told...replace the fuel filter!
even if it is new

[95C3500Cheyenne]

Patrick M. - Thanks for your and gmctd's help last fall. We have gone from 123k to 170k. I will be in nashville next week. I would like to see the mods you've done if possible.

[Govt issue]

check to see if the connector on the boost sensor is damaged. also check wiring for pinched places.

[99gmccrew]

Did you replace the resistor for the fsd?