? For 2008 Duramax owners

[DoubleGProstaff]

I bought my first Duramax last February and the last week or two she has been starting bad and putting herself into limp mode when I start her in the morning. Also my headlights and interior lights including my dash will dim then get brighter. My best friend who is my mechanic can't figure out why. Is it an electrical short? Bad alternator. I'm not much of a mechanic so figured id ask y'all on here. The codes were pulling are all codes that say communication problems. Any help is appreciated.

[Buckshot-73]

How old are the batteries?? Should have a mm/yr. sticker on them.

If over 4 yrs. old, replace both. Even though only 1 may be weak.

[DoubleGProstaff]

We changed them out in the last 6months before we found out my auxiliary battery wasn't helping crank the motor, it's battery cable wasn't even connected.

[DoubleGProstaff]

She has only started doing this since it's gotten cooler out.

[dhillis]

maybe a bad ground. Check over at dieselplace.com The forum there has actually had a split since I sold my duramax, and I can't remember the name of the other diesel forum.

[MacDaddy67]

fuel filter needs changed...not enough fuel pressure will send it into limp mode which will not run at idle thus affecting the charging system

[texaslammer]

fuel filter needs changed...not enough fuel pressure will send it into limp mode which will not run at idle thus affecting the charging system

this, I bet he nailed it

[twistedmidnite]

Does the dmax have a grid heater in the intake like Cummins? Cummins will cycle the grid heater on cold mornings and it will dim the lights when it cycles on.

[BluDiesel]

Mine had trouble when it got cold once, it was bad batteries.. These trucks are very sensitive to fuel filters and fuel pressure, I would not doubt if you had a dirty filter!

[bhodges317]

??

[DoubleGProstaff]

I just swapped out the fuel pump assembly last month and my symptoms started after the install. Maybe it's a crazy filter it came with.

[TxGiant]

I just swapped out the fuel pump assembly last month and my symptoms started after the install. Maybe it's a crazy filter it came with.

Possibly could have gotten a bad fuel pump that is on its way out? Also check and replace the fuel filter just so you can cancel that out.

[DoubleGProstaff]

Just pulled the codes again and have high rail pressure. Code p0088 I think

[BluDiesel]

Yup, change filter and get yourself a fuel rail shim kit.

[DoubleGProstaff]

Shim kit?