Check engine light while towing

[Capecodboater]

So I have had my truck 2014 Sierra DC 4x4 5.3)
for a few months or so (bought it with 33k) and whenever I tow my boat around in tow/haul mode I get a check engine light on the dash. The boat weighs about 6k and I only tow it an hour or so each way. The codes clear themselves a few trips after the haul every time.

Codes are p2096 and p0171

Any thoughts? I am bringing it in to dealer on Tuesday morning but the codes have already shut off.

Thanks for the help

 

[98trck]

I did a quick check and it looks like lean condition codes
when was the last time you ran fuel injector cleaner thru the engine?
so you may have some clogged injectors
fill the the tank up with premium gas see if it makes a difff
I know it helped my truck when I towed my trailer