Oil pressure light

Was out for a drive tonight and the oil light started flashing. Owners manual of course says park it, oil pressure low and your motor is about to explode. Oil level is ok, no leaks I can see. The pressure gauge read normal the few blocks I had to get home.

So after I checked that out I searched here and what I see is this can be a common problem. I do have a couple of questions I am hoping you guys can help with.

1) Is the oil light tied directly to what the pressure gauge is reading or not? I ask because if the light is flashing
and the gauge reads normal, can I trust the gauge more than the dummy light?

2) Do any of you have the SOS oil pressure sensor upgrade kit installed and do you recommend it? After
reading about it, it looks like a good upgrade.

1) No. The sender for the dummy dash light is located on the oil filter pedestal. When you change your oil filter, have you noticed a single little wire going to a sensor nearby? That is the dummy light sender and it is activated around 5-10 psi per the service manual.

Your dash oil pressure gauge is from a different sending unit located on the front head bank. It is buried and hard to see. Does your dash gauge show plenty of movement (rise/fall with engine RPM)? Does it basically act the same as it always has? If so, then you may consider driving the car until you get the sender fixed for the dummy light. The fix may be as simple as repairing a loose connection near the oil filter, or a broken wire. It sounds rare to have a failed one, so I would still be cautious if it were my vehicle.

If you're brave, you can take it up to 5800 RPM under a load and try to get VTEC engagement. The VTEC solenoids have their own oil pressure senders in each front and rear bank. If those senders don't read a minimum oil pressure at those load and engine speed conditions, then the hotter cam lobes will not engage.

2) It does look like a good upgrade if your OEM one dies. I would not recommend replacing a functioning unit with the SOS one. There have been a few instances on this forum of people having problems with the SOS replacement if you do a search. If yours is bad, then I would replace it... but not a functioning one!

Dave

Before anything else measure oil pressure off of the oil sandwich plate. There is fitting for pressure gauge in there. Look at the manual to find out more. At idle you should be around 1.5 kg/cm^2 and around 4 at 3000 rpm. Engine at op temp. I wouldn't rev it beyond that until you know you have proper lubrication. And it's just monitoring that's failing.

But I think you're having connection issues for the dummy light. Like Mac Attack was suggesting about loose wire etc

Thanks for the posts.

The gauge is operating between 200-500 kPa after the light came on. I was never much higher than 3000 RPM on the short drive home and figured it was ok to get that far. After checking it out I started the car again and the light did not come on, although I didn't take it back out on the road.

I will check the connection at the sensor and see how it looks.

As noted by others, the oil pressure warning light is operated by a separate switch that is independent of the sending unit for the gauge. The oil pressure switch is closed when there is no / low oil pressure which completes a connection to ground and cause the light to come on. When oil pressure is adequate, the pressure causes the switch to open up turning the light off.

Don't bother looking for a broken or loose wire. If the wire to the sender is broken or the connector is loose, the light will not come on. If the oil pressure is good and the light is on, then the switch has failed in the closed position (I had this occur on another car) or the insulation on the wire to the switch has frayed and the wire is now making contact with a body part somewhere causing the light to go on.

Jack the car up and remove the right rear wheel. This should give you access to the oil filter pedestal and the switch that is mounted on it. The switch is covered by a rubber boot. Disconnect the yellow / red wire from the switch and turn your ignition switch to run. If the oil pressure light stays on, then you know that you have a short to ground in the wiring some where. If the light does not come on, then you know that you have a switch failure or a low oil pressure problem. If you have the appropriate stuff and inclination, you could probably rig up a test of the switch. The easier thing would be to go out and buy a new switch, R&R the switch and then test it to make sure that the oil pressure light goes out when you start the engine. If it doesn't, then the money you wasted on the new switch is the least of your worries! Given that the gauge continues to read OK, I think the balance of probabilities suggests a failed switch.

As a note, the wiring diagram for the switch says that the switch is closed with low / no oil pressure and open with good oil pressure. The test procedure in the 1991 service manual says that the switch should be closed when there is no oil pressure (agrees with the wiring diagram). The test procedure in the on-line version of the 1997- 2005 service manual says that the switch should be open when there is no oil pressure; however, the oil light wiring diagram for my 2000 is the same as for the 1991 cars, so for this particular case I think that the test procedure in the 1997 - 2005 on line manual is incorrect.

Old Guy said:

The oil pressure switch is closed when there is no / low oil pressure which completes a connection to ground and cause the light to come on. When oil pressure is adequate, the pressure causes the switch to open up turning the light off.

Don't bother looking for a broken or loose wire. If the wire to the sender is broken or the connector is loose, the light will not come on.

Click to expand...

Ah, so that's how it works, huh? What a crappy design. A proper design would have been the opposite to alert the operator during instrumentation failure. I completely removed my low oil pressure dummy sender with an engine rebuild anyways....

I learned something new on the NSX today - Thanks!

Dave

Did the car have a major service recently?

Mac Attack said:

Ah, so that's how it works, huh? What a crappy design. A proper design would have been the opposite to alert the operator during instrumentation failure.
Dave

Click to expand...

Not necessarily. In my experience, the oil pressure switch normally fails in the closed position causing the oil pressure light to come on all the time. It may cause a panic attack; but, normally the driver will take notice and investigate. With this design, if the oil pressure switch by some chance sticks permanently open or the sensor wire breaks, then the driver should notice because the light will not come on when all the other dash lights light up at the beginning of the start sequence (I have to admit that I have become so used to Honda reliability that I normally don't check that anymore).

If you want to be super safe, you need three independent systems to measure pressure and they vote based on which two systems agree.

Old Guy, thank you for the detailed response. I will check it out. I dug out a 1997 service manual today, but hadn't been able to look at it too much yet. I will look into a secondary system and see what people are doing.

Larry, just over 57k on the car now, last timing belt service was dec 2012 at 50k. What got me thinking about this so hard is 500 miles before I bought the car the service record shows valve cover gasket replaced due to a leak. Like I mentioned, everything looks fine, but I am just being cautious.

HONDA9000 said:

Larry, just over 57k on the car now, last timing belt service was dec 2012 at 50k. What got me thinking about this so hard is 500 miles before I bought the car the service record shows valve cover gasket replaced due to a leak. Like I mentioned, everything looks fine, but I am just being cautious.

Click to expand...

The reason I ask is I had an issue a few years ago like this, and the last guy who worked on the car prior to me had pinched the oil pressure sender wire in between the rear valve cover and the head, and it was causing an intermittent grounding of the oil pressure sensor wire, kicking the light on with little predictability.

Regards,
LarryB

Finally got the car up to look at it. It all points to the sensor so in a day or two I will have a new one. I saw no obvious damage to the wiring. Thanks again for the help. I will post after I get it done and tested. Hope it does the trick!

Got it in tonight and light still on. After the 30 seconds it flashes hi and low, but not on and off. Haven't seen that until now. Pressure gauge still reads ok. Took wire off and started, no light, no leak. Checked torque on switch, got it a bit higher to 13 ft/lbs per the manual. Attached wire and started, no light, but after looking at the switch again I have an oil leak now from around the switch. Done for tonight. Tomorrow will reapply thread sealer and install. Not sure why the leak popped up didn't have it before.

Well this stinks.



Oil filter base is cracked. Looks like a discontinued part (15301-PR7-A00) so no luck finding one so far. Going to need to find one off a scrap engine or weld this one unless I get lucky and somebody has one laying around. I am going to post in the parts wanted section and pray.

I don't see the crack.

The crack is right where the pressure switch is screwed in. Enlarge the pic you can see it. That's why I either got a light or a leak depending on how tight it was.

Old Guy So far all the sites I checked say it is in stock, but after I place the order I get the email saying it is not available. I called one of the local dealers here and they called American Honda to check availability and they also said discontinued. I did not try Del Ray. I did receive a reply on my wanted post from someone who thinks he has what I need and will let me know soon. I am hoping that works out as it is my best chance.

Sent you a PM.

I have a spare one since I went custom cooler and filtration with a dry sump.

Dave

Got a base installed tonight on the car. Everything checks out fine now. Thanks to everyone who contributed to my issue and helped get me through it. Mac mega thanks for coming up with the part and getting it to me so quick!