Proper Tools and Testing Procedures

DIGITAL VOLT/OHM METER
Use a digital volt/ohm meter (DVOM) with a minimum 10 mega-ohms internal impedance when testing an Engine Control Module (ECM) or related components, unless use of an analog meter is specified by a testing procedure. Analog meters have low internal impedance and cause circuit "loading" in low voltage circuits, resulting in inaccurate measurements and possible damage to components. Use of a DVOM is necessary to obtain accurate measurements and avoid damaging low voltage ECM circuits and components.


TESTING PROCEDURES
Always follow recommended testing procedures. Never ground or apply voltage to a circuit unless specified by a testing procedure. ECM's provide a regulated constant low voltage source to some circuits, which may require a minimum resistance (impedance) to operate. Directly grounding or applying battery power to these circuits could damage the ECM and cause a system failure.


SPECIAL SERVICE TOOLS AND MATERIALS
Use of Special Service Tools (SST) and Special Service Materials (SSM) may be required, depending on the nature of the repair. Be sure to use SST and SSM where specified and follow the proper work procedure.