Proper Tools And Testing Procedures

WHEN TESTING A CONTROL UNIT OR RELATED ELECTRONIC COMPONENTS;
To obtain accurate measurements and to avoid damaging low voltage circuits and components, use a Digital Volt-Ohm Meter (DVOM) with a minimum 10 mega-ohms internal impedance (unless use of an analog meter is specified by a test procedure).

Analog meters have lower internal impedance and will "load" low voltage circuits, resulting in inaccurate measurements and possible damage to circuits and components.

TEST PROCEDURES
Always follow recommended testing procedures;
^ Never ground or apply voltage to a circuit unless specified by a testing procedure.
^ The control unit provides some circuits with a regulated, constant, low voltage source which may require a minimum resistance (impedance) to operate.
^ Directly grounding or applying battery power to these circuits could damage the control unit, causing system failure.