Auto Repair Help


by Kyle McFadden

The engine oil light remains on after the engine is started. The light may flicker or glow dimly.

The oil light is turned on by an oil pressure sending unit. The sending unit provides the ground to the light when the oil pressure becomes too low. The sending unit is calibrated by the manufacturer but usually activates between 5-10 PSI. The oil light should come on with the key on and the engine off and go out shortly after the engine is started indicating proper oil pressure.

Low oil pressure can be caused by a worn oil pump, worn engine bearings, electrical defect or a malfunctioning oil pressure relief valve. Of course, low or no oil in the engine can also cause this symptom. The first step in the diagnosis is an oil level check. Since all of the other causes usually require major engine service, you should verify that the engine actually has low oil pressure (thus causing the oil light to come on and stay on). This should be done to ensure there is not a malfunction in the oil light circuit. Confirm the oil pressure by removing the oil pressure sending unit and temporarily installing a test gauge. On most vehicles, the oil pressure on a hot engine at idle should be at least 8-10 PSI. If the oil pressure is satisfactory, the most likely cause is a defective oil pressure sending unit. Confirm this by temporarily disconnecting the wire. If the light remains off, replacement of the oil pressure sending unit will be necessary. If low oil pressure is confirmed by actual measurement with a gauge, internal engine service will probably be necessary. You should consult a vehicle service repair manual for specific repair instructions for your vehicle.

Use caution when working around hot and rotating engine parts. Engine oil becomes extremely hot after the engine is operated for only a few minutes. Use caution when removing any component that seals or contains hot engine oil.

(Kyle has an affinity for Pale Ale and tooling on his 1956 Chevrolet Nomad Station Wagon.)

11 responses to “Diagnose Engine Oil Light Stays On”

  1. roma mwenda says:

    please what causes the corolla ae111 engine a4 to misfire especially when loaded or climbing a hill

  2. PC Fixer says:

    That nagging Check Engine light! So glad there’s not a direct correlation for PC’s 🙂

  3. Bill Thomas says:

    We seldom experience this with our trucks. Thanks for this!

  4. Geoff hunter says:

    Hi I have trouble with a2001 tddi focus engine cuts out wth no warning I can’t find anything wrong but have found that the oil light goes out when engine is started even with the oil pressure sensor disconnected ? , is there two sensors and if the oil sensor I not reading would this cause an engine shut down. Thank for your time

  5. mswazi says:

    i have Toyota corolla 1.3 1988 model the prblem is that the oil pressure light stay on.when I check the oil level it’s on required limit so what can be prblem?

  6. Gh70 says:

    Hi i have a question i replaced my oil pump on my daihastu sirion 2005 but it does not want to work?any advice

  7. Mark Smith says:

    where is the oil pressure sending unit on a toyota noah 2004 located light flickers when at operating temp. and sometimes stays on?

  8. Scoooby27 says:

    1993 ford ranger “check oil” lite stays on once engine is running. oil level checked/ level is good. can vehicle be driven to parts store to get “check oil” sending unit, oil and oil filter

  9. Williams says:

    I have a Toyota Highlander 2004 model that is using 2az engine. I just got a new engine but after the first day my oil light shows. And my mechanic says its an electrical issue. Ve driven it to distance witout any issues but the oil light is still on

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