Alright - for some background, truck is a 2006 GMC Sierra 2500HD LBZ. 313k miles. I've had it for about a year, and have had pretty much no issues other than maintenance. Mods include EFI live DSP5, tuned by Idaho Rob (I was told the tunes are: 1. Modified Stock 2. Tow 3. +140 4. +180 5. +230), Suncoast trans/TC, EGR delete, PCV reroute, S&B intake with dry filter, MBRP 4" exhaust, Fass lift pump, newer injectors, head gaskets, and a few other things.

My issue as of a few days ago was a loss of low-end power and LOTS of black smoke. This truck usually hardly smokes at all, even with the switch at 5. After some research, it seems like this could be due to a dirty MAF sensor and/or clogged air filter. I cleaned both and it's running a bit better, but I'm now getting a p0234 Overboost code. I've never gotten this code before, even with aggressive driving. I've read that custom EFI live tunes typically eradicate this code, so I'm wondering why I'm getting it. Other codes I pulled: 0504 (I know what this one is), 0381, 0650, 0234, 0087.

I plan to replace the air and fuel filters this weekend and see if that helps with anything. In the meantime, do you guys have any idea why I might be getting an overboost code? It also showed a low fuel rail pressure code (which is why I'm replacing the fuel filter), but that hasn't come back since I cleared it post-MAF cleaning. The only one returning is the p0324.

Other info: I recently had the interior apart to reupholster the headliner. I also swapped the cluster (long story), so I had the dash (that the DSP5 is mounted to) pulled out. I also snipped a few wires that went to an old CB antenna.

Thanks in advance for any help you may be able to provide.

 

since you have efi live it should be easy to make the adjustments there to fix the overboost code. see if Idaho Rob can do the adjustments.

as for the low power and black smoke, you where at the right place to check the MAF. also check that there is no boost leaks, blown boots, etc

 

I replaced all (literally ALL) of the steering components last week including the power steering gear box, which involved removing the boost tube to access the PS lines. It crossed my mind that maybe the boot was leaking so I double checked and everything appears tight. I pulled the MAP sensor out last night and cleaned that (it was pretty dirty) as well as replaced the O-ring on the MAF sensor, but I took the Jeep to work today so I haven't had a chance to drive it after cleaning the MAP and clearing the codes.

In the meantime, I did send Rob an email. I haven't heard back yet.

 

sounds good. let us know how it goes.

 

Well, I replaced the air filter and it seemed to help a bit but not a whole lot. I haven't gotten any codes other than the p0504 (which is a pesky wire somewhere) since cleaning the MAP and MAF, so that's good. The truck still just didn't feel right.

On top of the lack of low RPM power and excessive smoke, I'd noticed that the vanes seemed to be opening a lot more than usual both at idle and low speed driving. Not constantly sweeping back and forth like a lot of people experienced, but more than it should have. I started doing some googling and my symptoms seemed to correlate with the Vane Position Sensor, although not quite perfect. Now, when I got the truck, I noticed that the sensor's wire had a lot of tape around one section. I'd never had any issues with it, so I never messed with it. So last night I finally tore the tape off and see that the wire had been cut and spliced back together with bullet style connectors. I cut these out, soldered the wires together, and taped everything up nicely. I also cleaned the plug in the main harness while I was there.

There must have been some corrosion in one of those connectors, or the wire wasn't making good contact. After doing that, the truck is totally back to normal. I took it for a test drive, stepped on the pedal, and though 'Oh... THAT'S what it used to feel like!'. Needless to say, I'm very relieved. I'll still be installing the new fuel filter tonight once UPS drops it off, but it was definitely the Vane Position Sensor causing my issues.

 

thats great. thanks for the feedback.

that is definitely something that "internet diagnostics" may have never found

 

Yes, and troubleshooting is so much fun haha. It drives me crazy when you're searching forums for answers and there are twelve threads perfectly describing your problem, yet either zero replies or no resolution. Figured I would post here and potentially help someone out in the future.