I recently purchased a 2005 Chrysler 300C (5.7L V8) with ~167000 miles. I get an occasional Low Oil Pressure light when the engine is hot and idling in gear. By putting the car in Neutral or even Park, the pressure goes up and the light goes out. Local Chrysler dealer replaced the oil pump and Oil Pressure Sensor, but the problem persists. The explanation from Chrysler is that the engine is “worn-out”, which I understand to mean excess clearances between the bearings as a result of excess bearing wear.
My mechanic has verified with a mechanical oil pressure gauge that the pressure is actually within acceptable range. I don’t want to invest in a new PCM or an engine rebuild (I don’t plan on keeping the car long enough to justify that expense).
Having said all that, I am curious whether adjusting the idle speed (maybe +100rpm?) would keep the pressure up enough to prohibit the code? Being that this engine is “drive-by-wire”, this would require some sort of scanner-tuner to access the PCM and make the necessary change. However, I’m not sure that this would generate additional problems…
There you go. So the warning light is a bother, not a warning - unless it comes on at higher RPMs. Does it actually set a code when the light comes on?
Would a higher viscosity oil make a diff? I’d try that.
Now pressure problems while driving. I can see the warning light come on four or five times before it sets the code. My concern is that I have to be wary around inspection time, as it won’t pass with a recent CEL.
My mechanic and I worked around it this year (driving cycle, ~20 miles under 50 mph to set the OBD2 Readiness Monitors), but I’d rather not go through these gymnastics. Dealer actually tried 10w-30 to no avail. My mechanic suggested that since I do not have a full maintenance history on the car, there may have been synthetic oil in it at one point perhaps resulting in corrupted sensors (the oil pressure sensor has since been replaced).
??? Bo-oh-oh-gus!?
That’s what I thought. Any thoughts on adjusting the idle?
I don’t know anything about doing that on modern vehicles. Would that have an bad effect on the trans?
Does the OP sender operate by varying resistance? What about putting a resistor in line - just enough to make it not light up at idle?
I don’t think it is adjustable.
I would say move the trade date up and possibly putting in some kind of additive ( some kind of engine snake oil ) . The engine is worn out statement is most likely correct.
Raising the idle so the oil pressure come up will do nothing for the engine. It would just stop the light from coming on. It would not increase the oil pressure while driving. What viscosity oil does your car ca for? If it is 5 W30 then going to 10W30 will not increase the oil pressure when the engine is up to temp. !0W40 would.
You MUST use 5W-20 to avoid problems with the MDS (multiple displacement system).
A programmer for your car would probably allow a greater idle speed. A little research of available programmers would identify the feature. I can do this on my Mustang with a SCT programming tool but these cost about $400. It would help keep the light off but that’s about all. Wouldn’t really hurt anything. Pretty steep price for that.
So these engines require 5W20? You might check on forum specific to this engine and see. Usually you can go up or down a viscosity range and not cause anything terrible. Usually going up on a worn engine won’t be the end of the world but I am certainly not an expert on this engine as I avoid Chryslers.
My first suggestion would have been to try 5W30 or 5W40 instead of 5W20 but that might be a big no-no on this engine based on the above suggestion. Do your research and maybe ask a Chrysler service dept. that has likely seen this before.
The reason too thick of an oil might be bad is because the oil these days is used for a lot more than just lubrication. It is also a hydraulic fluid for valve lifters, variable valve time, timing chain tensioners, and such. You might help the oil pressure problem if the bearings are worn but mess something else up in the valve train.
Go to https://www.carcomplaints.com/Chrysler/300C/2005/ This doesn’t look like a particularly bad car overall, especially for a Chrysler. There are a few engine failures but not that many for as many of these they made.
What viscosities does the manual tell you are OK? There will be more than one, usually. Use the “thickest” of them. For example, 20W40 instead of 10W30, or 10W30 instead of 5W20.
Remember, the oil light is only a nuisance when it comes on at idle.
You could try another oil pressure sensor I guess. Might do the trick, there’s always leeway +/- in the specs for “acceptable, so ship it” where the sensors are manufactured. lf that doesn’t work I’d say just live with the warning light coming on, maybe a black tape solution is needed here. The engine is probably nearing the end of its life, and will need to be rebuilt in order to actually solve this problem. An amateur electronics enthusiast could probably figure out a circuit (might just be a fixed resistor or battery) to add between the sensor and the computer to prevent the warning, but it seems like a lot of trouble to go to when just ignoring it is the alternative. For emissions testing purposes, about the only thing I can think of that will turn off the light so they’ll test the emissions is an oil-thickening additive. That will turn it off for the test, but may damage the engine if continue to use, so do a drain re-fill with the correct oil spec afterwards.
Manufacturer specifies 5w-20. The Oil Pressure Warning Light only comes on at idle.
You might get a larger base of Chrysler-experienced helpers at allpar.com. I’ve gotten lots of help there for my Chrysler Corp. minivans.
If that stored code can keep your car from passing inspection, or if it’s bothersome when the OP warning light comes on at idle, some options seem to be:
- do nothing
- put in thicker oil or an additive temporarily before inspection, or for good
- try a different OP sender
- change the signal from the OP sender - maybe a resistor can be added.
Someone knowledgeable at allpar.com may be able to address how serious a problem it may be to try thicker oil, or how to trick the OP sender. Good luck and please let us know what you find.
Interestingly neither of my current vehicles offers a “range” option (2009 Ford Focus, 2005 Honda Odyssey 5W-20 only): (page 328 of the Odyssey manual if you’re curious)
I don’t own it anymore, but I don’t think my 2005 Chrysler Town & Country had options either, but I haven’t had that old beast for almost 2 years now, so my memory could be foggy concerning that.
Thanks Shanonia. I’ll post if/when I get this resolved as well as how.
I just checked the owners manual for my 2007 Town and Country: “SAE 5W20 engine oil is recommended for all operating temperatures.”