Abstract: An electronic battery tester is disclosed with normal test and cold test modes comprising: a first circuit for applying an AC current load to a battery under test to induce an AC signal across the terminals of the battery; a second circuit for measuring the induced AC signal and converting it to a first voltage potential signal which is a measure of the battery's internal resistance; a circuit for adjusting the first voltage potential signal to a second voltage potential signal; third circuit for generating a threshold voltage potential signal at a first value when the battery tester is in a normal test mode and at a second value when the battery tester is in a cold test mode; and a comparison circuit for comparing said second voltage potential signal to said threshold voltage potential signal to determine a condition of the battery.

Abstract: A multi-test, hand-held instrument and method for testing manifold absolute pressure (MAP) and mass air flow (MAF) sensors includes a housing enclosing a battery and an electrical circuit. The electrical circuit can test d.c. voltage output signals and frequency output signals from MAP/MAF sensors and can test continuity and battery strength. Electrical leads extend outwardly from the housing and are connectable to the sensor being tested. A pair of light indicators, comprising LEDs and resistors connected in parallel, are selectively illuminated to allow the test instrument to be used to test both MAP and MAF sensors, and to test these components on different makes and models of vehicles.

Abstract: A multi-test, hand-held instrument and method for testing engine sensors and ignition modules includes a housing enclosing a battery and an electrical circuit. The electrical circuit includes a first test circuit electrically interconnected with said battery for testing potentiometer-type, temperature-type and Hall effect type sensors and ignition modules, a second test circuit electrically interconnected with the battery for testing oxygen, reluctance and knock sensors, and a third test circuit for testing the battery in the instrument. A first switch selects between the first or second test circuits, while a second switch selects between a component testing mode and a battery testing mode. Electrical leads extend outwardly from the housing and are connectable to the engine component being tested.