Low Engine Oil Pressure Indicator Light

How the Circuit Works

The low engine oil pressure indicator light works in two ways: it flashes continuously following a momentary loss of engine oil pressure, or it comes on and stays on with a complete loss of engine oil pressure.

When the ignition switch is in ON (II) or START (III), battery voltage is applied to the low engine oil pressure indicator light. If the engine is not started, the closed engine oil pressure switch provides a ground, turning on the light. When the engine is started, the alternator provides an "engine running" input to the integrated control unit. With normal engine oil pressure, the engine oil pressure switch is open and the low engine oil pressure indicator light does not come on. If the engine oil pressure switch closes momentarily (more than 0.5 seconds) but then opens again, the YEL/RED wire at the integrated control unit will sense ground through the switch. The integrated control unit will then provide and remove ground for the low engine oil pressure indicator light through the YEL/RED wire. The light will flash on and off until the ignition switch is turned to LOCK (0). The flashing feature will not work until 30 seconds after the "engine running" input is supplied by the alternator. This delay avoids unnecessary indicator operation.

If engine oil pressure falls below 4.3 psi and does not increase while the engine is running, the engine oil pressure switch will stay closed. The low engine oil pressure indicator light will then come on and stay on.