Proper Testing Procedures

ANALOG VERSUS DIGITAL VOLT/OHM METERS
Unless use of an analog meter is specified by a testing procedure, use a digital volt/ohm meter (DVOM) with a minimum 10 megaohms internal impedance when testing an Electronic Control Unit or related components. Analog meters have low internal impedance and cause circuit "loading" in low voltage circuits, resulting in inaccurate measurements and possible damage to components.

TESTING PRECAUTIONS
^ Always follow recommended testing procedures. Never ground or apply voltage to a circuit unless specified by a testing procedure. Electronic Control Units 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 Electronic Control Unit and cause a system failure.

^ When measuring voltage at the Electronic Control Unit harness connector, disconnect harness connector first, then turn ignition "ON" as necessary.
^ To prevent deforming Electronic Control Unit harness connectors, do not probe terminals directly. Instead, insert a pin from the harness side and perform measurements through pin.
^ Never pierce ignition leads or insulator boots to connect timing lights or analyzers. Use proper adapters.
^ Never apply battery power to a component unless directed to do so in a test procedure.
^ Do not create any arcing to check the continuity of a circuit.

SELF POWERED TEST LAMPS
Do not use a self powered test lamp to check continuity.