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If equipped, this gauge is located near the driver side of the instrument panel cluster.
This gauge indicates vacuum during light to moderate throttle and boost under heavier throttle.
This gauge displays the air pressure level in the intake manifold before it enters the engine's combustion chamber.
This gauge is automatically centered at zero every time the engine is started. Actual vacuum or boost is displayed from this zero point. Changes in ambient pressure, such as driving in mountains and changing weather, will slightly change the zero reading.
Chevrolet Cobalt Owners Manual. Towing a Trailer (Automatic Transmission)
WARNING:
The driver can lose control when pulling a trailer if
the correct equipment is not used or the vehicle is
not driven properly. For example, if the trailer is
too heavy, the brakes may not work well—or
even at all. The driver and passengers could be
seriously injured. The vehicle may ...