Dodge Intrepid 3.2L low oil pressure light

I should add that the car is a 1999 model year, and I last changed the oil in early September, less than 1500 miles ago. -G

Hi Greg!

It's the same part on many Chrysler vehicles - definitely all LH's. As discussed before, it's 90+% certain to be the switch, but to be safe you should have your pressure checked with a mechanical gage.

It is a switch. I have no definite explanation for the apparent dimness (instrument brightness control does not affect the warning lights), unless it is not making the best electrical contact when the pressure is right on the edge of closing it - there's no hysteresis (snap action) of the contacts. Or it is flickering (duty cycling) around the closure point at a rate that makes it appear dim rather than flickering.

There are some that claim that dirt/moisture/corrosion can cause it to be on intermittently. While that type of leak path might explain the dimness, I find it hard to believe that it would pull enough current over the path that it would have to be on to complete the circuit. While I'm not ruling that out as a possibility, I very much doubt that to be the problem.

When the switch does go bad on its own, it does behave pretty much as you described it.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Possibly a faulty oil sending unit. I have also seen a few problems such as this (dimmly lit) oil lites and the cause was a shorted circuit board behind the Instument cluster. Like Bill says, have the oil pressure tested and you may as well replace the sending unit at that time. If you have good pressure and the problem persists, have the instument cluster checked out

Glenn Beasley Chrysler Tech

Thanks, Bill and Glenn for your replies! Update: So far, I haven't had the problem again. The night that the oil light did go on, I had driven through a puddle in the rain a short time before I saw the light, so I'm wondering if that is related. I hope it's not the instrument cluster! I do plan to get the pressure checked. Are there any tricks to removing the pressure switch? On my 3.2L engine, I believe it is the green thing that sticks out just below and to the left of the oil filter. The oil pressure switch part number appears to be 4608303AB (the AB is new since 2002) and runs about $14-15.

I sure wish it had a pressure guage on the panel to supplement the idiot light.

Thanks, Greg

When you replace the sending unit take the connector cap off and remove the rubber seal, slide it up the wire or cut it out. Then replace the sending unit.

Glenn

>

I went through my records one year after I purchased the car, there was a service invoce for

-found oil leaking from oil pressure sensor, also found transmission fluid leaking from trani.

-cooler lines replaced oil pressure sensor tightened

- all clamps for cooler lines cleaned away fluid produced by leaks, roadtest, rechecked

- found leak at oil cooler line, took part, applied teflon tape, retightened, no leaks

Under parts, there was a 4608303 (the old part #). All of that was done under warranty.

I believe I taken it back after an oil change that time because the smell of oil was strong. I was surprised that they had done all of the above, as after an oil change the oil that inevitably falls out of the filter being removed spreads all along those lines, so I always wondered if there were really leaks or some spilled oil just wasn't cleaned (which I now know isn't easy).

Update: The engine oil pressure appears to be ok. (thank goodness!) The problem did reoccur, also on a day with heavy rains and a lot of water on the roads, which leads me to believe there is a connection.

As you might expect, I've been watching that light pretty closely. When it was on, it was on fairly dim. In daylight it was barely noticeable, and would have been missed completely if I wasn't watching for it. It did not appear to be flickering; if it was, it was flickering much faster than my eyes can see. (And my eyes are bothered by a monitor with a slow refresh rate.)

I just ordered some parts, including an OEM oil pressure switch. The part is cheap enough that I hope to replace it at the next oil change without too much trouble. I'll keep the old one to study it.

I still like my car and hope to get some more years out of it, even though it will turn eight in just 2.5 months. I'm not even sure what I would replace it with, the ample capacity and highway economy are a tough act to follow.

From what I understand about the switch, it closes at just under 5 psi. The BCM computer is not involved with the light, and it goes out as soon as pressure rises when the engine is started. Usually it flicker out just as the tachometer gets to about 1000 rpm, there is probably a little lag with the switch moving. It comes on a little sooner than the computer powered lights because it comes on when the key is in the OFF position, just before you turn the key to ON thence to start. The only other red or amber warning light that operates in a similar manner is the brake warning light.

Since oil pressure requirements increase with engine RPM, it would be nice if a warning light triggered at a higher PSI when the engine is moving faster, but we can't have everything I guess.

That would be called a gage! :)

The pressure switches generally get out of calibration when they start leaking into the connector cavity. The sealed cavity builds up pressure that works on the opposite side of the diaphragm that actuates the light switch - so the trip point is effectively shifted higher (i.e, instead of the original 5 psi, it now takes 7 or so psi to trip it - so the light comes on during normal but low pressure situations: Warm engine, in gear, idling. The problem becomes random as the connector cavity pressure fluctuates due to temperature and the oil slowly leaking into and back out of the cavity in both directions with engine off and run times.

There is a TSB on this problem that has them replace the pressure switch

*and* replace a seal on one of the unused wire holes in the harness connector with a "vent tube" - costs about $15 or $20 for a $0.02 piece of wire with crimp terminal that fits into the connector body like a regular wire except it only acts as a vent (no electrical connection). That's kind of a bandaid, since a good (non-leaking) switch will not exhibit the problem (though there can be some minor temperature effects due to the air that is contained within the sealed cavity - but probably not enough effect to be significant).

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Yeah, I thought that sounded familiar.

Yes, I'm familiar with that TSB, I believe it is 08-36-99. (And bless my library for having all of the TSBs). It doesn't show up until I search under

2.7L engines, and indeed it seems to only apply to 2.7L engines. I have a 3.2L. However, the pressure switch is the same part number, so go figure. I'm still curious about the rain/oil pressure light correlation.

The TSB says that allotted time for the repair is just twelve minutes. Good luck getting the car in the bay and up on the lift, and then down again in that time, to say nothing of installing that 'vent.'

Update: After several weeks of happily driving without an oil pressure light, it happened again. It had been raining heavily and I thought I saw the light on very dimly near the beginning of my drive, but then I didn't see it again...until....

I hit a puddle on the left side, I heard the splash of water spray from the wheels and simultaneously the oil light came on, not as dim as it had been before, but still dimmer than when the key is in the OFF position.

So that all but confirms the problem is caused by water. I recently bought a MOPAR oil pressure switch for about 12 bucks part # 4608303AB. I plan to change it at my next oil change, expected later this month. Of course perhaps the problem is not at the pressure switch, but I think that's a pretty good guess, especially given its very low location on the 3.2 L engine. Question: when I replace the switch do I reuse a rubber seal? The switch just has a connector, no seal, I'm not sure what the other pieces look like until I get under the car.

Thanks to all who responded, especially Bill and Glenn.

Are you sure that the switch is bad and it's not just shorting the terminal to ground through the water that's splashed on it? Try some dielectric grease on the connector and see if that doesn't make the problem go away.

good luck

nate

Greg - I'm surprised to find that water could make it come on (due to the current needed to light the bulb and no close direct path to ground)

- others, including Glenn I think, have told me that could happen, but I've always been skeptical. I guess it's time to start believing it. You do say it only comes on very dimly, so I can save face. :)

The rubber seal is built into the harness side of the connector.

Because it does appear to be a water/corrosion situation, be sure to clean the harness side of the connector (terminal and all surrounding insulation) real well with a commercial contact cleaner (from auto parts store) and fill the connector cavity with electrical-grade silicone grease (in the little condom-type foils on the counter at the auto parts store) before mating it to the switch.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

The oil switch is actually a pressure transducer, but in order for the switch to work properly it must be vented to atmosphere. The problem is when the vent of the switch gets plugs with dirt or any other contaminates such as oil from the leaking switch. the operation of the switch is altered because the switch cannot compare the outside air pressure to the oil pressure created by the engine. clean out the harness end of the switch thoroughly, I always disassemble the connector and remove the rubber seal or just pull it back. There was a TSB on this back for the 1999 LH to do this plus to add a wire terminal vent.. Do this and your problem will be gone..

Glenn

The normal failure mode is that the oil leakage (around or thru the switch diaphragm) causes pressure on the ambient (connector cavity) side of the diaphragm which works against the normal engine side pressure, causing the light to come on (not just dimly, but *on*, even though perhaps intermittently).

Greg's problem is that the light comes on dimly when it gets wet. Ironically, usually I'm the one saying it's internal oil leaking and you are the one talking about moisture causing a current leak path. In his case, it appears to actually be moisture related (which you always had a hard time convincing me of - I've finally come around to seeing it your way in some cases). But if he replaces it and cleans everything, that will cover both potential causes.

I don't think the connector cavity is normally vented - it is normally sealed. The adding of the wire vent per the TSB (in place of the seal in the unused second wire hole of the harness side of the connector) just prevents ambient-side pressurization *if* the switch were to start leaking (which would not be the case with a new switch - not right away anyway).

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

It is normally vented, I didnt know that untill I researched it this morning. And the purpose of the TSB was to allow for the vent.

Well, the oil light is a nice energy efficient LED, so it probably doesn't take much juice at all to make it light up a little. If it was a bulb, I"ll bet I never would have seen anything.

Ahh yes, I recall that the connector is bright green colored. Hopefully I can just remove and put back the rubber seal.

Good tips. I will have the vehicle up on a lift, but once I'm there I will have to already have everything I need to work on it, so that's good to think about ahead of time. Hopefull there won't be too much corrosion. Realistically it might be more likely that the connection is the weak spot, but for a few bucks I don't mind replacing the sensor too. The threads are precoated, so I assume I won't need to use teflon tape (I would use gas/oil approved tape anyway).

Thanks! The TSB I have for the wire terminal vent says it only applies to 2.7L engines though. I have the 3.2L. From what I understand the location of the switch in the 2.7L is what makes the vent necessary.

The TSB applies to 1998 and 99 vehicles that use the one wire oil lite system. and this includes the 2.7./ 3.2 The newer ones have had that vent installed already. If the newer models get plugged from oil,or dirt or whatever a cleaning is all that is needed along with replacing of the switch that is leaking. Just curious how many LH's do you have?

Glenn