Ford 1999 Ranger Owner's Manual page 171

Batteries normally produce explosive gases which can cause
personal injury. Therefore, do not allow flames, sparks or lighted
substances to come near the battery. When working near the battery,
always shield your face and protect your eyes. Always provide proper
ventilation.
When lifting a plastic-cased battery, excessive pressure on the
end walls could cause acid to flow through the vent caps,
resulting in personal injury and/or damage to the vehicle or battery.
Lift the battery with a battery carrier or with your hands on opposite
corners.
Keep batteries out of reach of children. Batteries contain sulfuric
acid. Avoid contact with skin, eyes or clothing. Shield your eyes
when working near the battery to protect against possible splashing of
acid solution. In case of acid contact with skin or eyes, flush
immediately with water for a minimum of 15 minutes and get prompt
medical attention. If acid is swallowed, call a physician immediately.
Because your vehicle's engine is electronically controlled by a computer,
some control conditions are maintained by power from the battery. When
the battery is disconnected or a new battery is installed, the engine must
relearn its idle and fuel trim strategy for optimum driveability and
performance. To begin this process:
1. Set your parking brake.
2. Put the gearshift in P (Park) (automatic transmission) or the neutral
position (manual transmission), turn off all accessories and start the
engine.
3. Let the engine idle for at least one minute.
4. The relearning process will automatically complete as you drive the
vehicle.
• The vehicle may need to be driven 16 km (10 miles) or more to
relearn the idle and fuel trim strategy.
• If you do not allow the engine to relearn its idle trim, the idle quality
of your vehicle may be adversely affected until the idle trim is
eventually relearned.
Maintenance and care
171