When filling or replacing the fluid of the power steering pump reservoir, use GM part #1050017 (or equivalent) power steering fluid only. Automatic transmission fluid may cause damage to the internal power steering components.
See Figure 1
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Power steering fluid level should be checked at least once every 12 months or 7,500 miles. To prevent possible overfilling, check the fluid level only when the fluid has warmed to operating temperatures and the wheels are turned straight ahead. If the level is low, fill the pump reservoir until the fluid level measures "full" on the reservoir dipstick. Low fluid level usually produces a moaning sound as the wheels are turned (especially when standing still or parking) and increases steering wheel effort.