Oil pressure light, not gauge?



I own a 1997 Dodge Ram 1500 4x4 with a 5.9L V8. It has 226,000 miles. It runs and sounds great. Currently the oil pressure light has been coming on after I drive 1 mile at 35-55mph after driving 65mph for 5 minutes or more. The gauge stays around 40psi for oil pressure, the light is the only thing that comes on. There are no unusual noises coming from the engine when the light flickers. Could it be the oil sending unit to the light? the oil pump? oil sludge clogging the pick up? or is it just getting tired? The oil has been changed every 3,000 miles. It’s next oil change isn’t for another 2,000 miles. Any help would be greatly appreciated. I’m new to car talk and it is a great resource!


Okay, dumb question, but you’re sure the light coming on isn’t an oil level light?

If it isn’t, then obviously the gauge and the light are getting different readings. The oil pressure should be checked with a mechanical gauge to see which one’s right-- with as many miles as you’ve got, the idiot light could be right. There’s usually a pressure switch for the light and a sender for the gauge.

It could also be the gauge itself. Does it move around or does it seem pegged at 40?


It’s a oil pressure light. I checked the manual to be sure. The gauge isn’t locked at 40, it will move from over 40 to a little under 40. It never is at 0 when the light comes on. Thanks


Replace the pressure switch that controls the light…Usually located near the oil filter, but not always…


The sensor gets tired after a while.


another thing…the light comes on when I am braking and coming to a stop and stays on until I press the accelerator and start moving again. At that point it turns off and doesn’t light back up until I brake and come to a stop. Usually lighting up around 15-20 mph when I am slowing down. Thanks.


That’s what made me think it might have been a level light.

I hate to say this, but I’m leaning towards the idiot light being correct and the gauge being wrong. It could be the oil pressure is really borderline and when you decelerate the combination of high oil temp and low engine speed could be causing the oil pressure to drop below the pressure switch’s setting. Having someone actually install a mechanical pressure gauge is the only way you’ll know for sure.


Thanks for the help. I don’t have a mechanical gauge, so I scheduled a time to get it checked out with a local mechanic. I think the screen to the oil pump might be clogged. The outside of the oil pan has chunks of rust falling off of it. It needs to be replaced. Could the same be happening on the inside of the oil pan and clogging the screen to the oil pump? I’m getting it checked out on Monday, I wish I could sooner but he is booked the rest of the week. Thanks again for the help.


Update: I got my truck back and they checked the pressure with a mechanical gauge and it was fine. So they replaced the oil pressure sensor. Now the gauge moves around more when I accelerate and decelerate. This morning the light starting flickering on again. The gauge didn’t read zero but where it does when it is idling. Since the reading was fine they didn’t look any deeper at it. The gauge works better but it still lights up after I have been driving for a while and everything warms up. It only comes on when I am coming to a stop and am stopping. Once I hit the accerlater it turns off.


Since a mechanical pressure check revealed no problems, I wouldn’t worry about this any further. At this kind of mileage, a lot of things are going to be tired and less than precise, including the gauge.