Oil warning light flickers but oil level is fine - so what's up?

For the last week or so the oil warning light on my dear old (1989) Corolla has had the alarming tendency to flicker. According to my owner’s manual, it’s not a problem if the light goes out once you step on the accelerator (which it does). But something must be wrong somewhere, else it wouldn’t be happening so much lately.

Pertinent facts:

  • I have in fact checked the oil level in the car about a dozen times this week since that damn light scares the bejeezus out of me. Cold engine or warm, the oil level always looks fine on the dipstick.

  • The flickering is more likely to happen in the first 15 minutes of my driving around, especially if I’m slowing to round a corner or go uphill. Regardless of when it happens, though, stepping on the accelerator always makes the light go out again.

  • The car does not sound or handle any differently than unusual.

  • I also once noticed a brief flickering of the brake light while driving (brakes & fluid are fine), as well as a flickering of the dashboard lights. But each of these things happened just once, whereas the oil light thing is an almost daily occurrence.

Anyone have any ideas?

The oil light usually monitors oil pressure, not oil level. There may be a transient or intermittent problem with the oil pump, or the oil filter may need changing.

My car’s (96 Acura) maintenance light will come on after 3000 miles from the last oil change. Every time I have the oil professionally changed, there is a button they press to reset the counter.

I believe there was something similar in my buddy’s 95 Honda. Perhaps this is your problem? I was able to discover this by reading my owner’s manual. A quick call to a Toyota dealership may shed some light on the matter.

If it’s an oil pressure warning, it could be a false indication from the switch going bad. But I doubt it.

My guess is it’s probably the pressure dropping due to normal engine wear. As your bearings wear, they present less resistance to oil flow, causing the oil pressure to drop.

Also, there could be debris in the pressure relief valve, causing it to not fully seat. If that happens, some oil can leak through causing a pressure loss.

Had an airplane with that problem about two weeks ago, as a matter of fact.

A flickering oil pressure light can mean one of several things.
[li]worn engine that does not produce enough oil pressure at idle[/li][li]an electrical fault in the wiring that gives a false indication[/li][li]an air leak on the intake side of the pump that causes air in the oil causing low OP[/li][li]Dirty oil causing a plugged oil filter.[/li][li]Bad oil pressure switch[/li][/list=1]

I suggest that you do this:
If the oil has not been changed recently have and oil and filter changed. Use a factory filter (some aftermarket filters can cause a drop in oil pressure) if the problem is still there, then:
Go to a reliable mechanic and ask them to preform a oil pressure test with a guage. Compare those reading to factory specifications for minium oil pressure.
if the reading is above min. suspect a wiring or switch problem.
If the reading is below min. look for issues inside the engine.

BTW some engine designs can run for years with the oil pressure light flickering at idle.

The sensors for oil pressure “idiot lights” do have an alarming tendency to fail and be unreliable in some cars. On a 1989 Toyota, I would say that it’s at least as likely the sensor has failed as there being an actual problem. Even with the behaviour you describe, it still could be a bad sensor.
Replacing the sensor is trivial for a home mechanic, and the sensor only costs about $10-20, so it’s something I would try first.

The T-28 used by the Navy as a trainer (many years ago) had an engine that needed a “sump pump” to keep the oil circulating. There was a warning light that would come on if the sump pump stopped pumping (or at least that was the theory). If that light ever came on we were ordered to immediately cut the engine and pick out a field to land in. The problem was that the light was more likely to be faulty than the sump pump. I knew one student pilot who successfully landed his plane and another who was ordered to bailout over the Gulf. I’ll bet some students took their chances on the faulty light.

Years ago a friend had a similar problem – the oil light went on even though he had JUST topped off all the fluids. So he figured it was “just the light” and went on his merry way. Some time later, his engine just started making funny noises and then stopped altogether. Turned out the oil was in there all right, just not getting to the engine due to a blockage of some kind. Completely ruined the engine, dead as a doornail. Get it checked out. Whatever it is, even if it is really just a faulty sensor, it will be a darn sight cheaper and less annoying than having a blown engine.

Yep, same thing happened to me MLS.

My '95 Sable does exactly the same thing.

I fixed it with electrical tape.

Lemme guess, you put the tape over the light, eh? That’s what I’d do…


As mentioned, it is entirely possible its the sending unit (or switch). They can and do fail with some regularity.

However, you’ll need to get your pressure checked with a mechanical gauge to be certain your pressure really is fine. Any decent shop should be able to do this without difficulty. Once that is done and it is verified that your engine is producing good pressure, you can replace the sending unit. Generally a “relatively” inexpensive, easy job.

If you sending unit is fine, it is more serious. Depending how low your pressure really is you may not need to worry about it though… yet.

Check to see if the wire to the sender unit has become unattached. I had that happen once. The clip on the end of the wire would then occasionally hit the block, shorting to ground, and the light would come on.