Not all tachometers are compatible with the Toyota electrical system. You are cautioned to check with the dealer and/or the tachometer manufacturer about suitability for your car. After a proper unit is selected, you may have to make or buy an adapter to connect the tachometer test lead to the Toyota terminal.
The electrical system and computer(s) are easily damaged through careless work habits. Since electricity travels at close to the speed of light, damage is instantaneous and expensive. Always observe the following rules when connecting the tachometer.
Do not leave the ignition switch ON for more than 5 minutes when the engine is not running.
The tachometer lead must only be connected to the correct terminal; accidental contact with another terminal can cause great damage.
Once connected to the terminal, the tachometer lead and connectors must be protected against grounding to any metal surface of the car. It is highly recommended that any adapter have fully insulated connectors or be wrapped in dry cloth or tape for protection; otherwise, the igniter and/or ignition coil can be damaged.
Never disconnect the battery cables while the engine is running.
Make certain the engine and ignition wiring is connected properly before connecting the tachometer. It is particularly important that ground circuits be clean and tight.