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post #1 of 4 (permalink) Old 07-25-2019, 10:08 AM Thread Starter
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Intermittent Oil Light

2010 Cobalt - intermittent oil light 2.2L
I've got a weird one here and I'm out of ideas.
About 2 months ago, I was on a short errand a block from home when my dash alarm chimed 4 times. I had never heard 4 beeps before, so I had no idea what it was. I looked at the dash, but there were no lights on or messages displayed.
This pattern persisted for the next 2 weeks. I drove 250 miles on Memorial Day without incident. Then the following Saturday, I was heading up a freeway ramp when I got the 4 chimes.
This time, the oil light was on. I found that at cruising speed, it went out, but when I accelerated, it turned on again. I babied it home and checked the oil. The dipstick says it's full.
I have 103K miles on the car (had it since it was new) and it has no history of burning oil.
On Sunday, I drove one mile without incident. On the return trip 2 hours later, the light was on steady when accelerating or at idle, but turned off at minimal throttle.
Monday morning, I took it to my mechanic. He diagnosed the problem as a faulty oil pressure sending unit. Replacing it fixed the problem - for 8 days. Then I started getting the same symptoms again.
So I started gathering more information about when and where the problem occurs. With two exceptions, I have never gotten a warning beyond the first 3 miles of driving. Those exceptions were about 10 miles in and I was on an incline.
I made a 250 mile trip last week and another 200 mile one this week. The blinking light occurred in EXACTLY the same place - a 6% grade at highway speeds.
There are no symptoms indicating that the oil pressure is actually low - no overheating even with summer temperatures. The scouting report is that the oil pump rarely fails on this engine.
The error is less likely to occur when the engine is cold. It may happen more than once in the first 3 miles. If I make a stop (short or long) it may happen again during the next few miles.
Sometimes I get a chime and a light, other times I get one but not the other. I had about a week without alarms following the 250 mile trip, but now alarms have returned.
There is some more than anecdotal evidence that an uphill or downhill stretch of road aggravates the problem. This may suggest that the oil level sensor is the culprit. But why did the alarms go away after replacing the pressure sensor?
Is the replacement pressure sensor defective? That's an outside possibility, but it's a stretch of the imagination.
Some friends have suggested a wiring or connector problem. But if that's the case, why does driving a few miles cure it?
I bought an OBDII reader - no codes.
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post #2 of 4 (permalink) Old 08-10-2019, 04:22 PM Thread Starter
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Well, it's been 2 weeks since I posted this. I've received quite a few views, but no comments. Does this mean I've stumped the band?
I think I solved it myself, and the solution is as bizarre as the problem.
I changed the oil filter.
My oil and filter were changes about 500 miles before all this started.
I was thinking about why this only happens in the first few miles of a trip. I wondered if the oil filter was draining down and had to refill after each start. It was a cheap guess, so 10 days ago, I swapped it out first thing in the morning after the car had sat all night. There was so little oil in the filter that when I dropped it onto my catch pan, the amount of oil that drained out was easily wiped up with a paper towel!
That was 11 days, 300 miles, and 35 trips ago, and no alarm bells or blinking lights.
After 3 months of angst, I'm happy again.
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post #3 of 4 (permalink) Old 08-11-2019, 04:57 PM
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Sorry for your troubles but glad you may have fixed the root cause to your problem! A defective oil filter can definitely cause oil pressure problems. Did you inspect the bad oil filter when you removed it? I’m curious to know if there is any obvious sign of the filter being defective.
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post #4 of 4 (permalink) Old 08-11-2019, 06:39 PM Thread Starter
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I saved it, but haven't dissected it yet. What should I be looking for? I am unfamiliar with these cartridge style filters. The last time I saw a filter like this was on my father's 1949 Ford tractor :-)

Last edited by Chuck Johnson; 08-12-2019 at 07:57 AM.
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