High oil psi and check eng light

[dieselshu]

My friend has a 03 SLT 2500, AUTO and has noticed a high oil (70psi) pressure reading at about 140 deg coolant temp as the truck is warming up, also at the same time the check engine light illuminates. Any ideas?



David

 

[ntenna]

OP gauge is virtual, so that reading will be anywhere the computer puts it for the engine speed and temperature; the computer is fed by a 6 lb. on/off switch. It typically reads 70+ until the engine warms, then 40 at speed hot. Programmed to "customer expectations".



Since the check engine light is coming on, it probably relates to some other issue (or non-issue) and may be causing the computer to keep the OP reading high... .



Time to have the dealer check the codes... .

 

[Prairie Dog]

Is your friend sure it's the check eng light and not the check gages light? It's somewhat common for this lamp to flash once in a while until you get a few thousand miles on it. Dealers are unplugging and then reconnecting the computers to alleviate this malady.

 

[rbattelle]

According to the service manual, the oil pressure relief valve opens at 75 psi, and the gauge doesn't care what the real pressure is as long as it's between 6 and 75.



DON'T GO BY THE FACTORY GAUGE!!! It's not a true gauge. ntenna is right... it's a "virtual" gauge.



Hook up an alternate gauge to the 1/8 NPT fitting on top of the oil filter mount. That will tell you for sure. Specs are: minimum 6 psi at idle, max of 75 psi, minimum 30 psi at 2500 RPM.

 

[Steve M]

Here we go with the virtual gauge thing again. Can someone point me to the source of this information. My gauge reads like a real oil pressure gauge with regards to rpm and engine temp. If it's a virtual gauge, they went to a lot of trouble to make it read like a real gauge.

 

[ntenna]

Steve, it's in the factory manual, both printed and CD. Under electrical, dash, gauges, oil. Explains how at 6 pounds the switch sends the computer an "oil pressure is on" signal, and the computer registers an oil pressure reading "programmed to customer expectations. " Below 6 pounds the gauge drops and the check engine light comes on.



Our trucks are now so smart they can out-smart US... ... .

 

[rbattelle]

Some relevant quotes from the service manual. Page 8J-32 and 8J-33:



"The oil pressure gauge gives an indication to the vehicle operator of the engine oil pressure. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the PCM on vehicles with a gasoline engine, or from the ECM on vehicles equipped with a diesel engine... "



And the following paragraph summarizes the "electronic messages" mentioned above:



"The instrument cluster circuitry restricts the oil pressure gauge needle operation in order to provide readings that are consistent with customer expectations. Each time the cluster receives a message from the PCM or ECM indicating the engine oil pressure is above about 41 kPa (6 psi) the cluster holds the gauge needle at a point near the middle increment within the normal range on the gauge scale. "

 

[bmoeller]

Kinda defeats the purpose doesn't it. They should have just stuck in an "idiot " light if that's all it's good for.

 

[Vaughn MacKenzie]

Retarded

That sure is pathetic!



I had a mechanical gauge on my 2001 for a long time, and the stock oil pressure gauge was VERY close and TRACKED with the mechanical one. Freak coincidence? Maybe the 2nd gen trucks had a REAL oil pressure circuit using a strain gauge sensor. I had my gauge plumbed into the same gallery very close to the oil pressure sender.



Vaughn

 

[ntenna]

Same with my '01, Vaughn. I'm pretty sure they were designed to read directly. Evidently Ford has been doing this virtual gauge thing for a while. Don't know about GM, though.

 

[Scooby]

IS the Speedo virtual too??

So if we get pulled over for speeding can our excuse be that our speedo was reading well within the margin of posted speed limits as per my expectations!

 

[ntenna]

Good one, Scooby!



Next up, virtual police officers which pop up in the dashboard

 

[rbattelle]

I love how the manual reads "... above ABOUT 41 kPa (6psi)... ".



What does "about" mean? Is that like 6psi +/- 5psi?