Proper Tools and Testing Procedures

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 with a minimum 10 Meg ohms internal impedance unless use of an analog meter is specified by a test procedure.

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

Never ground or apply voltage to a circuit unless specified by a testing procedure. The engine control module provides some circuits with a regulated, constant, low voltage source which may require a minimum resistance (impedance) to operate. Grounding or applying battery power to these circuits could damage the control unit.