What Exactly Controls the Boost?

[DA BIG ONE]

Can any of you tell me what operates the wastegate control valve on a 99 GMC SUB 6.5 TD?

The valve (new) stays closed not allowing any vaccuum to get to the wastegate. Vac pump sucks 25 psi, all line are tight w/o leaks.

I got a bad stumble when traveling back home sunday, straight run about 3 hours, truck seemed to be fine, but the next day the SES light came on right away and somehow the boost control circuit failed, like it is not getting a signial from the ecm.

[CareyWeber]

Originally posted by DA BIG ONE:
Can any of you tell me what operates the wastegate control valve on a 99 GMC SUB 6.5 TD?

The valve (new) stays closed not allowing any vaccuum to get to the wastegate. Vac pump sucks 25 psi, all line are tight w/o leaks.

I got a bad stumble when traveling back home sunday, straight run about 3 hours, truck seemed to be fine, but the next day the SES light came on right away and somehow the boost control circuit failed, like it is not getting a signial from the ecm. DA BIG ONE,

The wastegate solenoid controls it.

Do you have a 1500 or a 2500 sub?

The 1500

[DA BIG ONE]

Originally posted by CareyWeber:
</font><blockquote>quote:</font><hr />Originally posted by DA BIG ONE:
[b] Can any of you tell me what operates the wastegate control valve on a 99 GMC SUB 6.5 TD?

The valve (new) stays closed not allowing any vaccuum to get to the wastegate. Vac pump sucks 25 psi, all line are tight w/o leaks.

I got a bad stumble when traveling back home sunday, straight run about 3 hours, truck seemed to be fine, but the next day the SES light came on right away and somehow the boost control circuit failed, like it is not getting a signial from the ecm. DA BIG ONE,

The wastegate solenoid controls it.

Do you have a 1500 or a 2500 sub?

The 1500

[a5150nut]

check ALL of your connections. Rubber hose ends and the plastic tubes too. The plastic tubers are easly cracked/broken from bending. Some have replaced entire lines with hose. I was thinking of steel tubing. Hmmm, how small do they make brae lines?

Anyway, did you check vacume at the pump end also or just at the turbo? Confirm the vacume pump is working properly. Then check each leg of the line. 20/25 at pump and vac side of solinoid. I just checked mine at turbo and was getting 15/17 at turbo.

[Kennedy]

Could be the solenoid itself. If replacing it does not work, then check the ground ckt from the solenoid. The PCM pulses the ground based on duty cycle.

If you don't have gauges, add them now.

[DA BIG ONE]

Originally posted by kennedy:
Could be the solenoid itself. If replacing it does not work, then check the ground ckt from the solenoid. The PCM pulses the ground based on duty cycle.

If you don't have gauges, add them now. So, can I conclude if there is no ground pulse from the PCM then it is going south, or?

[Kennedy]

Or bad wire...

I guess the first thing I'd do is get a Tech 2 on it and command 100% duty cycle then recheck the ground signal. From there, check the ground wire to the pin at the ECM and then the PCM pin to ground.

[DA BIG ONE]

Originally posted by kennedy:
Or bad wire...

I guess the first thing I'd do is get a Tech 2 on it and command 100% duty cycle then recheck the ground signal. From there, check the ground wire to the pin at the ECM and then the PCM pin to ground. Thank you, will do.

[C.K. Piquup]

DA BIG ONE,Did you get it fixed yet?When you do,let us know what you found and what you did.Good Luck and then,Thanx