Abstract: A hand-held apparatus for testing cable harness for faults and performance impairments comprises three sets of voltage references, CMOS comparator circuitry, programmable DIP switches, an LED status display for error detection, an LED for indication of overall system condition, and a power source. The voltage dividers are utilized to determine reference voltages; each voltage divider comprises a resistor pair. In the preferred embodiment a first set of voltage references is utilized for checking open conditions and is generally associated with odd-numbered wires in the cable harness. A second and a third set of voltage references may be employed for all types of testing, with the second set of voltage references being generally associated with odd-numbered wires and the third set of voltage references being generally associated with even-numbered wires.