2006 f150- temperature gauge stays cold but "check gauges" flashes in mini message center.

Knowing how these gauges work , I'd say you have an instrument cluster problem not oil sender unit. 2003 - 2006 GM had bad stepper motors in the instrument cluster . If there was a problem with the oil sender the gauge would default to zero .
Engine Oil Pressure Gage
The instrument panel cluster (IPC) displays the engine oil pressure as determined by the powertrain control module (PCM). The IPC receives a class 2 message from the PCM indicating the engine oil pressure. The engine oil pressure gage defaults to 0 kPa (0 psi) or below if:
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The PCM detects a malfunction in the engine oil pressure sensor circuit.

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The IPC detects a loss of class 2 communications with the PCM.

If you don't know what class 2 serial data communications are ,google it. How to repair GM Instrument Cluster Speedometer Gauge Stepper

Replace the oil sending unit. On top of the engine, in the center by the fire wall.

check your coolant. the temp is the water temp. Your radiator is out of water? you`ll burn out your water pump. Also check to see if your radiator fans are running constantly.

Did you try changing the actual oil pressure gauge?

Oil Pressure Test Check for proper oil pressure at the sending unit passage with an externally mounted mechanical oil pressure gauge. A tachometer may also be needed, as some specifications may require running the engine at a specific RPM.

1. While the engine is cold, locate and remove the oil pressure sending unit.
2. Following the manufacturer's instructions, connect a mechanical oil pressure gauge and, if necessary, a tachometer to the engine.
3. Start the engine and allow it to idle.
4. Note and record the oil pressure reading when the engine is cold. The engine may need to run at a specified RPM, if so check the vehicle's specification.
5. Run the engine until normal operating temperature is reached.
6. Check the oil pressure reading again with the engine hot and record the value. Turn off the engine.

Compare the hot oil pressure reading to the specification. If the reading is low, check the cold pressure reading against the specification. If the cold pressure is well above the specification, and the hot reading was lower than the specification, the engine may have the wrong viscosity oil. Change the oil, making sure to use the proper grade and quantity, and then repeat the test.
Low oil pressure readings could be attributed to internal component wear, pump related problems, a low oil level, or oil viscosity that is too low. High oil pressure readings could be caused by an overfilled crankcase, too high of an oil viscosity or a faulty pressure relief valve.

Item Part Number Description 1 — Tachometer 2 — LH turn indicator 3 — Oil pressure gauge 4 — Overdrive (O/D) off/tow haul indicator 5 — Engine temperature gauge 6 — Air bag warning indicator 7 — Safety belt warning indicator 8 — Fuel gauge 9 — Tire Pressure Monitoring System (TPMS) warning indicator 10 — Speed control indicator 11 — Transmission temperature gauge 12 — RH turn indicator 13 — Speedometer 14 — Malfunction Indicator Lamp (MIL) 15 — Message center indicator display area 16 — High beam indicator 17 — ABS warning indicator 18 — Brake warning indicator 19 — Message center display area 20 — Anti-theft indicator

Bad head gasket or cracked head

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You better put a manual gauge on your engine and make sure you have oil pressure. Could just be a faulty gauge or sending unit but I sure as heck would be checking it with a manual gauge.

Hello mb4494: My name is Roger and I will help you. If by changing the oil pressure sending unit the problem did not change. I would perform a oil pressure test. This is done by removing the oil pressure sensor and inserting a oil pressure gauge. This can be done by yourself or by a repair shop. This needs to be done on a cold engine. Start the engine and observe the oil pressure cold.as the engine warms up observe the pressure. The pressure will drop off as the engine warms up.Should the oil pressure drop below 10 to 12 PSI. then you have internal engine trouble. More then likely a bearing problem. Try dropping the truck into gear and see what the pressure drops off to. Again if the pressure drops below 10 to 12 PSI. you have a problem. I would also check to make sure you have the correct oil switch. a truck with a oil light uses a oil pressure switch. with a gauge you would use a oil pressure sending unit. Sorry for the long reply but want to make sure you check the pressure correctly. Please rate the quality of the answer as this is how we know the answer was correct. Thank You for using Fix Ya. Roger

Is the needle going to the red part or the upper 3/4 part of the gauge?

If so you definately have an overheating problem. The car will run fine until it's too late.

Check the following:

1. Electric fans are coming on at temperature
2. Take off oil filler cap and check colour of oil. Creamy brown color indicates water getting into oil passages through head gasket or cracked oil passages in block.
3. Take off radiator cap when cold and check for coolant color as per step 2. Also check for coolant flow when keeping engine revs up. If not much flow (should be like a river flowing), could be blocked radiator.
4. At operating temperature hold top then bottom radiator hose with hand. If either of these 2 are still cool it indicates a faulty thermostat.

Otherwise water pump fins could be corroded.

Hope this helps :)