stock in dash oil press idiot light gauge

[brods]

Would it be possible for someone with an electronics background design a circuit board to convert a standard oil pressure sender to work with the stock in dash oil pressure gauge on the 3g's with the fake gauges?

 

[rbattelle]

Not likely. You'd have to have a pretty intense background in electronics and computer programming, because the logic for the idiot gauge is embedded in one of the vehicle computers itself.



However, it *might* be possible to design a new gauge mechanism that mates with the back of the stock gauge needle and connects to a standard pressure sensor, thereby giving you a genuine stock-looking pressure gauge with real motion. But I suspect the cost and effort associated with such an undertaking would make it a waste of time and resources.



-Ryan

 

[KBennett]

Is there an oil pressure sending unit on our trucks?

 

[bighammer]

Is there an oil pressure sending unit on our trucks?

My understanding is that it's not really a sending unit, but more of a switch. If it senses oil pressure, the computer makes the needle move to where it thinks it would be on a real oi pressure guage.

 

[Bow66tie]

This is why I chose an oil pressure gauge to use in my 3 gauge dash pod. My '93 D250 had the stock oil pressure gauge go goofy on me about 1200 miles from home. We originally thought the engine ingested portions of a Napa oil filter and plugged up the motor. Wound up being the sending unit. I swore I'd never be without a back up oil pressure gauge again, and with the 3rd gens having nothing more than a nice looking idiot gauge in the dash, that's on of the first mods I installed.



Michael

 

[brods]

Not likely. You'd have to have a pretty intense background in electronics and computer programming, because the logic for the idiot gauge is embedded in one of the vehicle computers itself.



However, it *might* be possible to design a new gauge mechanism that mates with the back of the stock gauge needle and connects to a standard pressure sensor, thereby giving you a genuine stock-looking pressure gauge with real motion. But I suspect the cost and effort associated with such an undertaking would make it a waste of time and resources.



-Ryan

Bummer. I was hoping something relatively simple, like a 5v signal sent to a traditional sending unit that was wired directly to the existing gauge could have worked. Been there done that switching gauge bodies and faces in a stock cluster, it wasn’t all that hard..... but here once again DCX throws a curve. From the service manual:



CAUTION: Instrument clusters used in this model automatically configure themselves for compatibility with the features and optional equipment in the vehicle in which they are initially installed. The instrument cluster is programmed to do this by embedding the Vehicle Identification Number (VIN) and other information critical to proper cluster operation into electronic memory. This embedded information is learned through electronic messages received from other electronic modules in the vehicle over the Programmable Communications Interface (PCI) data bus, and through certain hard wired inputs received when the cluster is connected to the vehicle electrically. Once configured, the instrument cluster memory may be irreparably damaged and certain irreversible configuration errors may occur if the cluster is connected electrically to another vehicle; or, if an electronic module from another vehicle is connected that provides data to the instrument cluster (including odometer values) that conflicts with that which was previously learned and stored. Therefore, the practice of exchanging (swapping) instrument clusters and other electronic modules in this vehicle with those removed from another vehicle must always be avoided. Failure to observe this caution may result in instrument cluster damage, which is not reimbursable under the terms of the product warranty.



Kind of rules out getting a junkyard cluster and modifying it. I wanted to avoid having the top of the dash full of gauges, but I guess there is no other option :{

 

[KBennett]

I sent a PM to Scott Bentz (sbentz on TDR), to get the facts. Scott is the VP of Rocky Mountain Cummins and said that the output of the oil sending unit is just a switch, not a varying analog output. They had too many false readings that caused problems. The computer sends the oil pressure gauge a value as long as the engine is running and there is pressure.

 

[rweis]

With an added REAL OP sensor / gauge you can cross check the fake gauge (psi yes / no) with real data. You will also get a feel when the engine is warmed up by the stabilization of OP psi from startup readings (cold 80 psi, warm 65 psi).



I did OP because that is one of the engine conditions that would cause an immediate shutdown to save the really BIG engine $$$$. Sensor and gauge as I recall were less than $150. Cheap insurance.



Bob Weis

 

[rbattelle]

I sent a PM to Scott Bentz (sbentz on TDR), to get the facts. Scott is the VP of Rocky Mountain Cummins and said that the output of the oil sending unit is just a switch, not a varying analog output.

Link.



-Ryan

 

[GaryCarter]

What it would take to get this done would be a hack of the ecm/pcm (I forget which it is right now). Plus installing a sensor and finding an unused sensor input to the ecm to read. A pretty complicated undertaking, but not beyond the skills of the people doing power boxes. Maybe some day one of them will throw in a real gauge option.



Gary

 

[brods]

Excuse my electronic ignorance, but why go through the ecm? Wouldn't isolating the gauge by "cutting the wires" so to speak and then driving the gauge directly be easier from an electronic perspective? Would disconnecting the gauge throw the instrument cluster computer into a fit?



Thanks for the replies.





IMHO the gauge should have a disclaimer under it. Something like:



"This gauge is for entertainment value only. The readings displayed are merely estimations, not measured values. The actual oil pressure may be different. " :-laf

 

[MRFost]

Excuse my electronic ignorance, but why go through the ecm? Wouldn't isolating the gauge by "cutting the wires" so to speak and then driving the gauge directly be easier from an electronic perspective? Would disconnecting the gauge throw the instrument cluster computer into a fit?



Thanks for the replies.





IMHO the gauge should have a disclaimer under it. Something like:



"This gauge is for entertainment value only. The readings displayed are merely estimations, not measured values. The actual oil pressure may be different. " :-laf

Electrical Engineer here -- this is the way to do it. While in there, you can fake the dash into thinking the gauge still works. But I don't have time to do this, and I have way bigger problems, so sorry ... but I wanted you to know that this would be the best approach.

 

[kmcdonough]

I read this thread, as well as Ryan's thread, and the question I have is... . isn't the OP guage supposed to be there for a reason? To indicate if there is a potential problem? I don't know too much about our engines but I think that too little or too much oil pressure would indicate a potential engine problem. If our idiot guages are only switches to tell us pressure or no pressure whats the point? Why do we even have a guage? Or am I missing something? Can we still derive useful info from these guages?



Kevin McD.

 

[rbattelle]

Why do we even have a guage?

Because it "looks cool", I guess. No other reason.



-Ryan

 

[KBennett]

Because it "looks cool", I guess. No other reason.



-Ryan

Kind of like a "stick-on" hood scoop :-laf



I am going to check into this gauge thing and see what I can come up with.

 

[FASTERTHANU]

General consensus in our engineering group is that the reason the switch goes through the ECM is so that if there is a low pressure condition the ECM will turn the engine off and therby protect it much faster than you or I looking at a gauge every once in a while... . can anyone confirm our guess?

 

[brods]

Doubtful. I don't even want to imagine the liability aspect of randomly shutting down the engine, especially if it is because of a failed pressure switch rather than low oil pressure. No engine rpm = no hydro boost for the brakes



From the 2005 service manual "... Engine Oil Pressure Low Message - Each time the cluster receives three consecutive bus messages from the PCM or ECM indicating the engine oil pressure is below about 41 kPa (6 psi), the gauge needle is moved to the red graduations (except SRT-10) or to the red zone (SRT-10) at the far left end of the gauge scale, the check gauges indicator is illuminated, and a single chime tone is generated. "



Single chime? Should be like a fire alarm!



kmcdonough, the gauge is useful to tell you if the oil pressure is above or below 6psi, that is all.

 

[rweis]

BIG rough tough truck!,



Gotta have gauges, looks COOL



even if they are just short of meaningless.



Bob Weis

 

[cyborg]

should be a law suit somewhere here.

Selling a sensor and gauge but deviering a switch and light.

 

[nickleinonen]

No engine rpm = no hydro boost for the brakes

not true is you have a hand shaker. . and you have the accumulator in the system to give you power brake boost enough for one application [still no power steering if your engine isn't turning]