Q&A

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....

next: fake out the computer with attaching a resistor of "good" size and installing an auxiliary electronic gauge to the oil pressure sensor....

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..