GMC 2005 Sierra 1500 Pickup, Owner'S Manual, Page: 386 / 574

Maintenance When Trailer Towing
Your vehicle will need service more often when you’re
pulling a trailer. See Scheduled Maintenance on
page 6-4 for more information. Things that are especially
important in trailer operation are automatic transmission
fluid (don’t overfill), engine oil, axle lubricant, belt,
cooling system and brake system. Each of these is
covered in this manual, and the Index will help you find
them quickly. If you’re trailering, it’s a good idea to
review these sections before you start your trip.
Check periodically to see that all hitch nuts and bolts
are tight.
Trailer Wiring Harness
Your vehicle is equipped with one of the following wiring
harnesses for towing a trailer or hauling a slide-in
camper.
Basic Trailer Wiring
All regular, extended cab and crew cab pickups have an
eight-wire trailer towing harness.
For vehicles not equipped with heavy duty trailering, the
harness is clipped to the vehicle’s frame behind the
spare tire mount. The harness requires the installation
of a trailer connector, which is available through
your dealer.
If your trailer is equipped with electric brakes, you can
get a jumper harness (electric trailer brake control)
with a trailer battery feed fuse from your dealer.
If you need to tow a light-duty trailer with a standard
four-way round pin connector, you can also get an
adapter form your dealer.
4-92