Reduced Engine Power Supercharged Silverado

Hey everyone. Im having an REP situation that would previously throw P1516 P2101 before I increased the parameters to 80%, but this was just a band-aid. The vehicle has ran fine for the last year and a half, then started going into REP and the throttle body basically fluctuates like the ECU cant hold it in position anymore. The throttle body and harness, pedal and harness, and ecu have all been replaced to no avail. All the GM VIS diag procedures have been followed and pinouts have been checked.

I don't see a smoking gun in the tune or in the logs, but I can see APP at a given percent like 100% and the throttle body will only open 45ish percent and fluctuate and if you stay in it long enough it might eventually slam wide open and go, or sometimes lift off the pedal and stab it again and it will go WOT. Engine off I can work the pedal and throttle body tracks perfectly.

I don't know who tuned it but a/f are really good and runs really good, when it does run, but Im just trying to get it throttle body to act right and vehicle to be reliable again.

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When you say harness - whole harness or just pigtails?

Nick came out with upgraded tb motors and electronics for this reason, so might not hurt to give his shop a call - Nick Williams. From my experience when you're having tb issues raising the "allowed error" settings is the wrong thing to do. They always seem to get worse after that. Unless the blower is pullied and moving a lot of air or mounted wrong, a stocker shouldn't have those problems.

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It's a miracle it ran right for any length of time.

None of the VE's populated? Something the OP did or original? I'm surprised it would crank and keep running.

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Originally Posted by GHuggins

When you say harness - whole harness or just pigtails?

Nick came out with upgraded tb motors and electronics for this reason, so might not hurt to give his shop a call - Nick Williams. From my experience when you're having tb issues raising the "allowed error" settings is the wrong thing to do. They always seem to get worse after that. Unless the blower is pullied and moving a lot of air or mounted wrong, a stocker shouldn't have those problems.

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Just the pigtails for both throttle body, and accelerator pedal. It has an OEM GM stock size throttle body on it.

I noticed the VE table was all zeroed, which seemed odd to me. I have very little Gen 4 experience. It fires right up and runs completely off MAF from what it seems. This is a totally different operating system then what I'm familiar with.

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Originally Posted by FlatlineSilvia

I noticed the VE table was all zeroed, which seemed odd to me. I have very little Gen 4 experience. It fires right up and runs completely off MAF from what it seems. This is a totally different operating system then what I'm familiar with.

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It's a 2bar enhanced OS. Whomever did it didn't know what they were doing. You need to fill in the VE tables for all of your transient fueling and low speed driving. I'm actually surprised the transmission or anything is working right with it being zeroed out.

That just shows how incredibly forgiving these PCMs are. Worst thing ever happened to the tuning industry was/were these PCMs.

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Originally Posted by GHuggins

It's a 2bar enhanced OS. Whomever did it didn't know what they were doing. You need to fill in the VE tables for all of your transient fueling and low speed driving. I'm actually surprised the transmission or anything is working right with it being zeroed out.

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So I have populated the VE tables and am going to give it an attempt as soon as I have time, but I did notice that above 4000ish RPM it starts showing VE readings in the log. How would that be without the VE tables populated? Also how does the VE table effect it going into REP or at least keep the throttle body from following the accelerator pedal input...?

You can see in the log where I go to WOT and the throttle body doesn't move off of 50ish percent... or I'm at wot and the throttle body is at wot and will just taper off to 40/50% with no real explanation.

VE directly relates to the map torque model. Map torque model directly controls the majority of the throttle and the commands to when the transmission will shift. Not to mention there are airflow correlation test and self checks that can cause problems on their own. Before replacing or going after anything else, I would do like Ed has hinted at and tune in your VE. Above 4000 the ecm will use the MAF input for everything, so your saving grace at that point. I haven't looked at the cal in detail like Ed has, but I'm willing to bet your map/maf correlation dtc's are set to no error and several map parameters are more than likely changed for it to run at all. Regardless, it has to be in a partial reduced power state at all times I would imagine. I know the ecms have the capability to calculate an "airmass" and VE from that. Newer ones will even self correct the VE based off of MAF flow up to a certain error.

OK I populated the VE tables and got them within a reasonable limit, but still no wide open throttle and TAC codes. What else am I missing...?

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It's possible your throttle tables have been changed. I compared to an 07 I had and they were different, but didn't check to see if the OS number was the same. Go to the repository and find a stock file for yours running the same operating system. Verify your throttle tables are still stock. If not, put them back to stock.