Engine/Transmission (1994 - 1998) 12V Oil Pressure Switch governed by PCM ???

[Katmandu]

My Oil Pressure on my 98 12 Valve has bottomed out a couple of times for no apparent reason. It will Zero out for like 1-2 Seconds during idle and then pop back up like nothing ever happened. Oil level is OK as well.

I just found a TSB about this issue, but the article doesn't differentiate between 12 or 24 Valve engines.

Is the 12 V Engine Oil Pressure Switch governed by the PCM ??

Here's a TSB saying the PCM requires a REFLASH if the Pressure Switch is "Bottoming Out".

http://dodgeram. info/tsb/1999/08-22-99.htm

 

[bmoeller]

The oil pressure gauge is controlled by the PCM. Given the age of the truck, it may be a bad sending unit. I would get a mechanical gauge to verify.

 

[Katmandu]

The oil pressure gauge is controlled by the PCM.

Would an EARLY 98 12 Valve still be controlled by the PCM ??

 

[Dieselnerd]

I don't have my 12 valve manual anymore but as I recall the PCM has nothing to do with the oil pressure sender on a 12 valve engine.

 

[JFaughn]

The tsb says 99 , the 12v was over in 981/2 I think. does that help.

 

[JTeague]

TSB 8-22-99 applies to 12 valve 98 trucks with engines built before Jan 5 of 98.

 

[Katmandu]

TSB 8-22-99 applies to 12 valve 98 trucks with engines built before Jan 5 of 98. #ad

... ... ... ... .....

 

[JTeague]

Where do you get your information Katmandu? I just rechecked to make sure on Dealerconnect at the dealer and TSB 8-22-99 specifically states in BIG black bold print that is for Pre JAN 5 98 12 valve engines. NOT 24 valve engines.

 

[obert]

Try checking the wire harness connection at the oil press. sensor.

 

[SchulzR]

I had the same problem a week ago. Its the sensor located on the drivers side of block. Its about a $35. 00 fix. Not fun to change but the problem will go away!

 

[bmoeller]

I was wrong. Looked in my powertrain diognostic book this morning. Oil pressure gauge is NOT controlled by the PCM. Also, it has no input for the oil pressure to the PCM either, so if you loose pressure, it won't shut the engine down.

 

[CumminsPower98]

The PCM does indeed control the gauge on a '98 12v. I have had past problems with mine dropping to 0 at hot idle so I changed the sender with an aftermarket one and that fixed it the first time for a few years then it started it again so the next time I put in an OE sender and it didn't really fix the problem for long. I finally went to a dealer to get the TSB done and the first time they couldn't find any TSB on it even though I gave them the number so they tested pressure and said it was fine and sent me on my way. Next I printed out the TSB and took that too them and this time they did the flash, which fixed the problem. Yes I know this TSB just turns the gauge into an idiot light by not letting it drop below 40 psi but at least I don't have to listen to the chime everytime it drops. I would like to some day have good oil pressure and water temp gauges. My temp gauge pegs once it gets at the 3/4 point rather then going slowly up to the top. So it seems that when it is reading at the 3/4 point it is actually around 230.

 

[Berrigan]

Just did the TSB on my truck this morning. Ill post again latter to let you know the results. I think the oil and temp gages work the same way. At some point the pcm is programed to start the alarm condition. (obviously this alarm point is adjustable with a reflash) when this alarm point is reached the oil gage goes to zero, or the temp gage goes to 230. Its like the gage is not allowed to read above or below a certain point even though the sender is changing its value, then when the alarm point is met the gage zips over to its extreme readind and we get the alarm. Im pulling these numbers out of the air but oil gage shows 20, actual press drops to 15, gage is told not to read 15 and drops to zero and alarms. Your pulling heavy up a grade. temp rises to 210 gage goes to 210 temp rises to 220 gage stays at 210, temp rises to alarm point and the gage pegs at 230 and alarms.



Im not sure on all this but thats what I think is happening. Bill

 

[CumminsPower98]

I think you are right about how these gauges work at least that's how I have been thinking of it. I hate that, I just want a gauge that reads what's actually happening.

 

[Berrigan]

OK I have two days of driving after the tsb fix. No low press alarms yet, was getting them multiple times a day. I think its fixed. lowest press seen on gage is 40, but goes to about 65 at 70 mph. fyi, Bill

 

[Katmandu]

Just did the TSB on my truck this morning. Bill

What did the Dealer charge you to do it ??

My local dealer wants $75 to reflash my PCM for this TSB.

 

[Berrigan]

$100 bucks, ya I thought that was high too. They were 5 star though and had free donuts in the waiting lounge. (thats about 25 bucks a donut) Bill

 

[Katmandu]

$100 bucks, ya I thought that was high too. They were 5 star though and had free donuts in the waiting lounge. (thats about 25 bucks a donut) Bill

That's Sic. I can't stand the GREED of these places.

$75-100 for a reflash of the PCM that maybe takes a whole friggin' 5 MINUTES. #@$%!

There's GOT to be another way to get a PCM reflashed to fix this problem.

Anyone know of any chip Burners or other devices that are available to do this ?? I'd rather put $75-100 towards something like that that I could reuse later on.

 

[Johnstra]

My oil pressure alarm has just started doing this in the last couple of days. I have a second oil pressure gauge so I know my pressure at all times. Seems to chime when the pressure drops to 20 or below - which is very rare.



My question is: Why has this only just started happening? Reprogramming the PCM to not be so sensitive will make the alarm stop sounding but oil pressure is still going lower than it has before.



-john

 

[Berrigan]

My oil pressure alarm has just started doing this in the last couple of days. I have a second oil pressure gauge so I know my pressure at all times. Seems to chime when the pressure drops to 20 or below - which is very rare.



My question is: Why has this only just started happening? Reprogramming the PCM to not be so sensitive will make the alarm stop sounding but oil pressure is still going lower than it has before.



-john

Im not sure it is lower than it was before. Before I did the reflash I changed the sender. The problem did not recur for a couple months. Then it started doing it again. I think the new sender had a little bit more (or less) resistance at hot idle rmp than the old one. Just enough difference to make the problem go away for a while. I think the sender is whats changing and or manufacturing tolerances arnt the greatest and the reflash just puts a little more buffer in the circuitry to compensate and stop the ghost alarms from sounding when there is no real oil pressure problem. I am however not a Mopar engineer, this is just my take on the situation. Bill