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Wideband O2 monitor

The LC-2 should only be powered when the engine is running. I've also installed an electric power steering pump (EPS) which draws a high current, so if the ignition is left on the battery is quickly drained.

LC-2 manual:

Do not pre-warm the sensor before starting the engine, simply start the engine as normal. Allowing the sensor to pre-warm before starting the engine will increase the possibility of damaging the sensor from shock-cooling.
I came up with the idea of using a voltage monitor, so that the LC-2 and the EPS only receives power when the battery is charging, indicating that the engine is running. The voltage monitor has two configurable set-points, a start voltage and a cut-off voltage.

The voltage monitor controls a relay supplying the LC-2 (and the EPS) directly from the starter battery.


I mounted the hardware on a plate that I fixed to the back wall of the glove box. This provides easy access, as well as hiding the clutter away from view. A flyback diode is added to the relay to counter the EMF generated during coil de-energization.