Connect scan tool with 'DATA LINK CONNECTOR' (DLC).

Warm engine up to normal operating temperature.

Turn all the electrical devices including air conditioner OFF.

Monitor "BATTERY VOLTAGE" parameter on the scan tool.

Fig 1) "BATTERY VOLTAGE" data at idle after warming engine up.

☞ Check if the symptoms listed below occur as checking if battery voltage drops dramatically when turning on the electrical devices.

【The alternator of poor charging efficiency】

1. Lamps are dim at idle, while lamps are bright at acceleration.

2. Intermittently RPM drops excessively or engine shut down at low RPM close to idle state at times.

3. Smooth cranking happens rarely. (Warning lamps in cluster turn dimmer excessively at cranking and poor cranking happen.)

4. Charging lamp turns on during driving.