Power Circuit Probe with Live Waveform, 12V and 24V

The KZYEE KM50 is a powered circuit probe, not a meter. It taps the battery through a long lead and puts switched positive or negative current out at the probe tip, so you can drive a shift solenoid, a fan, a relay or a pump directly at its connector without pulling the component or jumping a relay socket. A 10A auto-reset breaker sits between the battery and the tip, so an accidental short trips and resets in a few seconds instead of taking out a fuse or a module driver.

What separates the KM50 from an older probe is the color screen. It runs seven test modes - DC and AC voltage, resistance, diode, frequency, duty cycle, fuel injection pulse and component activation - and plots the signal as a live waveform next to the digital value, with an adjustable sample rate. That matters on transmission work because the pressure control and shift solenoids on modern units are PWM driven: the TCM varies duty cycle, not just on and off. Backprobe the solenoid circuit, watch the duty cycle move as the command changes, and you can tell a TCM that is not commanding from a solenoid circuit that is not responding. A static voltage reading will not show you that.

The LEDs and buzzer call out polarity, voltage present, ground and continuity as soon as the tip touches, which is how most of a wiring job actually gets done - chasing a broken ground or a corroded pin in a case connector rather than reading exact numbers. It works on 8 to 30 volt systems, so it covers 12V cars and light trucks and 24V medium duty and marine. Sold as an upgrade of the earlier KM10.