VACHZHD

Our 2012 3500 SRW w/ 42,000 miles - check engine light came on the other day. Read the codes and had the following:

U101C - Lost comms with turbo module "a"
P0102 - mass air flow sensor "a" circuit low
P144F - egr cooler bypass status line circuit high
P144E - egr cooler bypass status line circuit low

The second two actually came up "proprietary" on my cheap meter... but this is what I think they are based on a quick web search.

No apparent performance issues other than the exhaust brake didn't work any more... kind of made sense with a loss of comms with the turbo.

Did a cursory check of connections and didn't see anything obvious. Checked fuses and didn't see anything obvious.

Took it to the dealer... they ran diagnostics for 1 1/2 days before finding a blown fuse (M21) that once replaced corrected the issue.

I obviously didn't look closely enough at the fuses and was somewhat embarrassed by that... but the dealer was equally embarrassed that the trouble shooting protocols took him a over a day to find a blown fuse... "we're supposed to perform them in the order the manual says..." Guarantee that tech will always check that fuse first if he has this code combination come in again...

Now didn't find what caused the fuse to blow... but it hasn't come back and hopefully is isn't an electrical gremlin that I'll have to keep chasing.

Wanted to share this so anyone seeing this code knows at least to check fuse M21 before launching more complex diagnostics.

Live and learn...

jgdfotog

Where is the m21 fuse. I'm having the same problem.
jim

BigIron70

I have had same issues recently, turned out being turbo actuator shorted. Since both the turbo actuator and the MAF sensor get power from M21 fuse. Both will set codes when fuse blows.

Busboy

Thanks for the input, that's something to keep in the back of the mind.

DodgeCowboy

Where is the m21 fuse loctaed? I have a mas air code that keeps coming up for no reason

Busboy

The fuses are in the PDC power distribution center under the hood drivers side.

1-2-3

Me too. I've done everything and it still comes back. I'm about to decide it's just a by product of putting an emission system on an engine that was never built to have one, and that some trucks do this and others don't. It's like Clint said, do you feel lucky.

I believe now that the only way I'm going to stop mine is to delete it. I've still been on the fence about doing this. My 04 was strait piped and it was loud. My son is driving it now and I never realized it is as loud as it is. I'm really enjoying the quiet on this truck. However, i did get next to a 6.7 the other day that was deleted with a 5" strait pipe and it didn't sound near as loud and had a deeper sound to it, that I think I would like. I stayed with him till he pulled off into his neighborhood. I'm half way tempted to go find the truck and ask the guy if he would show me what he has done with his truck. I wonder if that would be creepy or not.

Oh, my fuse is not blown. If I get a chance, I'd like to pull every single fuse and look at them closely. Thanksgiving week was my 5th week this year without OT and it's looking like it will be my last. Getting old.

Hymato

I'm having same issue no blown fuses and all the same codes and they won't clear.

johnh

check your fuses with a ohmmeter !t's far better than a visual inspection!

BigIron70

The fuse was blown because actuator is drawing too much current, code will come back when actuator pulls more current then designed to pull. Most likely you will need a turbo in the near future.