Hummer 2007 H2 Owner's Manual page 216

This light should come on, as a check to show
you it is working, when the ignition is on and the
engine is not running. If the light does not
come on, have it repaired. This light will also
come on during a malfunction in one of two ways:
•
Light Flashing — A misfire condition has
been detected. A misfire increases vehicle
emissions and may damage the emission
control system on your vehicle. Diagnosis and
service may be required.
•
Light On Steady — An emission control
system malfunction has been detected on your
vehicle. Diagnosis and service may be
required.
216
If the Light is Flashing
The following may prevent more serious damage
to your vehicle:
•
Reducing vehicle speed
•
Avoiding hard accelerations
•
Avoiding steep uphill grades
•
If you are towing a trailer, reduce the amount of
cargo being hauled as soon as it is possible
If the light stops flashing and remains on steady,
see "If the Light Is On Steady" following.
If the light continues to flash, when it is safe to do
so, stop the vehicle. Find a safe place to park
your vehicle. Turn the key off, wait at least
10 seconds and restart the engine. If the light
remains on steady, see "If the Light Is On Steady"
following. If the light is still flashing, follow the
previous steps, and see your dealer for service as
soon as possible.