Digital Volt/Ohm Meter (DVOM)

Engine Control Module (ECM) and Related Component Testing
Use a Digital Volt/Ohm Meter (DVOM)--minimum 10 mega-ohms internal impedance--unless test procedure specifies otherwise.
- To obtain accurate measurements and avoid damaging computer related circuits and components.
- Analog meters have lower internal impedance which will "load" low voltage circuits--resulting in inaccurate measurements and damage to components.

Never apply voltage or ground to a circuit--unless specified by test procedure.
- ECM provides regulated low voltage sources 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 or related circuitry.

Follow test procedures carefully.