GMC Yukon XL Denali 2005 Owner's Manual page 433

Ignition Transmission Lock Check
While parked, and with the parking brake set, try to turn
the ignition to LOCK in each shift lever position.
•
The ignition should turn to LOCK only when the
shift lever is in PARK (P).
•
The key should come out only in LOCK.
Contact your GM Goodwrench
required.
Parking Brake and Automatic
Transmission Park (P) Mechanism Check
CAUTION:
{
When you are doing this check, your vehicle
could begin to move. You or others could be
injured and property could be damaged. Make
sure there is room in front of your vehicle in
case it begins to roll. Be ready to apply the
regular brake at once should the vehicle begin
to move.
®
dealer if service is
Park on a fairly steep hill, with the vehicle facing
downhill. Keeping your foot on the regular brake, set the
parking brake.
•
To check the parking brake's holding ability:
With the engine running and transmission in
NEUTRAL (N), slowly remove foot pressure from
the regular brake pedal. Do this until the vehicle is
held by the parking brake only.
•
To check the PARK (P) mechanism's holding ability:
With the engine running, shift to PARK (P).
Then release the parking brake followed by the
regular brake.
Contact your GM Goodwrench
required.
Underbody Flushing Service
At least every spring, use plain water to flush any
corrosive materials from the underbody. Take care to
clean thoroughly any areas where mud and other debris
can collect.
®
dealer if service is
6-11