Check engine light is intermittent - 2001 Kia Rio

1. You need to have an independent oil pressure gauge hooked up to the engine to check the oil pressures at various RPMs and to verify the 40 to zero drop. This will eliminate any issue with the pressure gauge or the sending unit.

2. The oil pressure variation can be caused by an intermittent blockage in the oil pick up or an intermittent sticking oil pressure relief valve. I would possibly suspect the latter if you are getting good pressure and it is intermittently dropping to zero and going back up again..
If you or previous owners have not maintained the engine with frequent oil changes you will get a sludge build up problem in the engine and this will be evident by just dropping the engine sump.

3. If you have had a check engine light warning then you need to have the vehicle scanned to see what fault codes have been generated by the computer. There will be some related to the intermittent loss of oil pressure but there may be others also..

4. You need to have the oil pressure problem checked out immediately. Running the engine when you constantly lose oil pressure intermittently will definitely cause engine damage due to a loss of both lubrication and oil cooling to critical components.

check fuel pressures, clean and test injectors, replace HT leads with quality units

Auto zone or any parts store can plug in and read the code when it is active.

check engine light??if so then better bring it to the expert and try diagnostic scan to retrieve the fault code..if check engine doesnt light..try check your fuel pump pressure,might low pressured fuel or high pressured due to malfunctioned pressure regulator sensor..

2007 Chrysler Pacifica having intermittent fuel gauge problems. Goes from normal to dead/ low fuel. Has full tank. Also, check engine light is on

You need to check for fault codes, the check engine light is on because a fault is in the system. Here is how to do a fault code test, no special tools required. Follow the link please. FAQ How to read older GM codes for free

check your cruise control unit first

the 1st thing u need to do is have the system computer tested for trouble codes, anytime the light comes on a trouble code is stored, there are over 200 of these codes for potential system malfunctions, yours sounds like a O2 problem.

The only way to find out what the problem is is by doing a scan of the car computer module using an OBD code reader.
The codes returned will tell you the cause of the problem.

brake light switch located on the steering column by brake peddal