GMC 2008 Savana Van Owner's Manual page 306

TPMS Sensor Matching Process
Each TPMS sensor has a unique identification code.
Any time you rotate your vehicle's tires or replace one or
more of the TPMS sensors, the identification codes will
need to be matched to the new tire/wheel position. The
sensors are matched to the tire/wheel positions in the
following order: driver side front tire, passenger side front
tire, passenger side rear tire, and driver side rear tire
using a TPMS diagnostic tool. See your dealer/retailer
for service.
The TPMS sensors can also be matched to each
tire/wheel position by increasing or decreasing the tire's
air pressure. If increasing the tire's air pressure, do not
exceed the maximum inflation pressure indicated on the
tire's sidewall.
To decrease air-pressure out of a tire you can use the
pointed end of the valve cap, a pencil-style air pressure
gage, or a key.
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You have two minutes to match the first tire/wheel
position, and five minutes overall to match all
four tire/wheel positions. If it takes longer than
two minutes, to match the first tire and wheel, or more
than five minutes to match all four tire and wheel
positions the matching process stops and you need to
start over.
The TPMS sensor matching process is outlined below:
1. Set the parking brake.
2. Turn the ignition switch to ON/RUN with the
engine off.
3. Press the Remote Keyless Entry (RKE) transmitter's
LOCK and UNLOCK buttons at the same time for
approximately five seconds. The horn sounds twice
to signal the receiver is in relearn mode and
TIRE LEARNING ACTIVE message displays on the
DIC screen.