dodge ram van 2500, 110,000 mi. 5.2 l engine. At idle and after warm up, Check Gauges light comes on and and oil gauge needle falls to zero. Replaced sensor and tested pressure with manual gauge confirming 12psi. Multiple techs/garages are stumped...
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1998 Dodge Ram Van 2500
Question: computer misdiagnoses low oil pressure at idle
dandd February 25, 2010, 18:53Master
If you mean 12 psi at idle then that is decent oil pressure. I would suspect the Instrument Cluster Computer or a bad CAN bus line. What does the oil pressure data say on the scan tool? You can read this, I have done it. Check the engine computer and compare it with the Instrument Computer, they should be the same!!
ReplyRonQ, March 13, 2010, 04:00Rookie
Temporarily attached variable resistor for sending unit, turned it and saw the gauge move. Dash board flags "bad" oil pressure when gauge is at 1/4 upscale. Sensor is good for lower pressure(s) as confirmed by Ohmmeter test. Dash board control is faulty - and who fixes the wrong/bad trip point reference in the (which?)-computer?
My code reader has only "read set codes" function, and it can erase them. The dash board has it's own computer? figured it is part of the Engine Management Computer. May be it is part of the Power Train Computer? In any case in the "good old days" one could just replace the oil gauge and be done with it; now you have to take the car to the "Shop" and spend extra time and money - and - have to give up control of the project - and - risk being at the mercy of (revenue hungry) strangers....
Thank you for any additional help.
PS. sure seems like a "factory built-in, bring-in the customer for revenue when the vehicle is old enough" thing....since I am a programmer, I know, that this is possible to do..
..found where it said 6 PSI is adequate pressure....
ReplyRonQ, March 13, 2010, 04:54Rookie
next: fake out the computer with attaching a resistor of "good" size and installing an auxiliary electronic gauge to the oil pressure sensor....
Answer #2Visitor, March 18, 2010, 18:20
Before you worry about the computer, please be sure the correct oil viscosity was used. I believe that is 10/30. Verify that yourself. lighter oil viscosity will wreak havok on you! Low oil pressure light, check engine light, blow by, stalling, much fouling of the plugs and throttle body. Your oil will be black and reak of gasoline from the blow by. If this continues, your oil pump will die, and so will your engine. Also, (just as important) Please verify your oil level is not too high on the dip stick! If you have an overfilled crank case, all the symptoms stated before will be present. Too high of an oil level will cause the oil pump to whip the oil into a froth and it looses all lubracating properties. Your engine will act like a rabid chihuahua. You will think it is every senor on the engine, then you may realize all you need is a good engine flush, with proper oil change and filter. I hope this help.
ReplyRonQ, March 21, 2010, 03:05Rookie
follow up: because of the low oil pressure light, drained the oil with the purpose of replacing with heavier oil. Curious thing: draining resulted in 2 gal+1qt of oil! Replaced with 6 qt of 20-50 oil - still low oil pressure, only at idle after warm up. Dip stick show low oil level, used heavy , stiff wire to probe depth to bottom of oil pan, and compared that to length of dip stick - stick is 3 inches shorter! I bought the van used, from private person, just recently - I did not change dip stick - and must be wrong dip stick. Dip stick is not easy to buy or come by - so how come it is short -and who was "being ugly" to change it? I guess engine is worn and needs a high volume oil pump? The lifters still pump up within 1..2 seconds- in the morning from overnight shut down; no lifter noise, if I restart the engine in an hour or so.. Since the lifters pump up ok, the oil system can't be too bad. Still think the generic oil pressure sensor is bad or (more likely) has bad specs.. BWD made it. So I should find: right dip stick, right sensor,, and get the instrument module repaired for "bad low end display" of the oil gauge....compared generic sensor with factory part and generic sensor has 10psi spec and factory part has 5 psi spec...so I am now using the factory part and no more diagnostic code..
Answer #3Visitor, March 09, 2011, 14:06