Why is the code reading HP5 on the tempature read out?

That is the all systems operating normally code. If you are having running problems the most common issue is coolant tempature sensor reading wrong tempature or not at all. It usually makes the idle shacky they stink and no power.
The other thing is the ground wires on the intake manifold ,the body grounds, connections to the battery.
The most common misdiagnosed problems with your truck is melted catalyst converter, dead oxygen sensors and old fuel pumps.

It sounds tempature related I would check the engine coolant tempature sensor Its going to be near the upper radiator hose where it attaches to the engine block a false reading from this sensor could screw up other systems abiblty to give correct readings to the vehicle control system and cause a lot of unasual unrelated problems to acure If you can i would seggest that you take it to an auto parts store most will read the codes for free although you have what is called an OBD 1 SYSTEM on board dianostic system OBD 11 is the newer system its likely a sensor and you will likely be able to fix it for under 50 dollars mabey 20 Good luck with it

One thing you should know about a gas oven is that they do not keep a constant tempature like an electric oven does. So going by a tempature gauge in the oven can fool you. The way a gas oven works is by "average" tempature. In other words if you take the highest and lowest tempature readings and average them out you will get the actual tempature. For example let's say that you set the oven to 350. Well first it will take about 10 to 15 minutes for the oven to properly pre-heat. Once it is preheated you can listen to the gas burner and watch a tempature gauge(flook meter is best). When the gas burner shuts off the oven tempature will continue to rise. When the oven tempature stops rising then you will take that reading. Then wait for the oven burner to come back on again and watch the tempature gauge. When the tempature gets to it's lowest point and stops then take that reading. Do this several times and then take all the tempature readings and add them together then divide that number by the number of readings you took and that will give you the actual tempature. Within 5 degrees is great but anything over 10 degrees can affect your cooking. This will give you an idea if your oven is out of calibration or not.

There is a calibration procedure. The instuctions are located in the owners manual and can be found here http://products.geappliances.com/MarketingObjectRetrieval/Dispatcher?RequestType=PDF&Name=49-85131.PDF

Just go to the "Thermostat Adjustment" section for the proper calibration procedure.

Is this oven gas or electric? If it is gas then it can be normal to see 30 to 50 degrees difference in tempature. The tempature in a gas oven works on the average tempature. For example: The oven tempature may rise all the way up to 370 degrees. Then the burner will shut off. And then the tempature can drop all the way to 330 degrees. Then take 330 and add that to 370 then divide that number by two and the average tempature will be 350. If your oven is electric then the tempature should be much more consistant but can have a 10 to 15 degree variance. Also the standard oven tempature guage that you put in the oven or even the temp guage built into the oven are not very accurate. We us a Fluke meter with a thermocouple to calibrate an oven. So to check your oven for proper tempature regulation you will first need to let the oven pre-heat for about 15 minutes. Then place the thermocouple in the center of the oven. If the oven is electric the take a temp reading every 5 minutes and average them out. If the oven is gas then you will need to take a temp reading when the tempature reaches it's highest and lowest points. Take at least 5 consectutive readings and average them out. You should get an average within 10 degrees of set temp(350 degrees). If it is off by 35 degrees or less you can usually caluibrate the thermostat back to proper temp. This procedure can be different for each range model. If it is more than 35 degrees off or you are getting irratic readings then the thermostat or thermostat components might need to be replaced.

I would supect you actually have two problems going on here. First off it sounds like your guage is reading inaccuratly. When it is reading at one quarter it probably should be at the half way point. This is the normal operating range. The most likely cause is the temp sensor for the guage. When you pull a trailer and engine gets under a load the tempature sounds like its going up too high. Your engine light comes on because it uses a different sensor and is registering accurate tempature. I would start by comparing actual tempature of engine with what the guage reads, this can be done with a scanner or a heat gun pointed at the thermostat housing. I believe you will find a faulty sensor or possibly an outside chance of a bad guage.(but doubt it!)Once that is straightned out you will have to look at why is the engine getting too warm under load. I would start with radiator flow,A ristricted radiator either internally or externally will cause this. Good luck!

The F2 error code is due to the temp sensor is registering a tempature over 600 degrees. So the reason why the convection fan is continously running is because the ERC thinks the oven is overheated and is trying to cool it down. It is probably a bad tempature sensor or oven relay board. You will need to test the tempature sensor with an OHM meter. They usually will read 1000-1100 OHMS at room tempature. If you get an open read or a incorrect OHM reading then I would replace the tempature sensor otherwise replace the power relay board if the temp sensor is reading correct. But try unplugging the power to the oven for over 10 minutes first and then plug it back in. This will reset the ERC and might fix the problem.

The F2 fault code is usually for a out of limit tempature reading due to a faulty temp probe or excessive temp during clean cycle with door unlocked. If you have disconnected the power for over 10 minutes and the error keeps coming back then you will need to test the tempature probe to see if it is defective. Test with a OHM meter and at room tempature most probes should read around 1100-1300 ohms. if the reading is way off or open then replace the tempature probe.

That is a bake range over tempature error. First try disconnecting the power to the range for more than 10 minutes and see if the error re-appears. If it does then you will need to test the tempature probe with an ohm meter. At room tempature the probe should test 1000 to 1100 ohms. If you get a reading that is out of range or different ohms than rated replace the probe. If the probe tests good then replace the control.

RTD is resistence tempature detector. The oven is telling you that the tempature probe circuit is open. The temapture probe may have been damaged due to the self-cleaning cycle or it could just be the wiring harness is loose. You will need to remove the tempature probe and test it with a ohm meter. The average reading should be aroun 1200 ohms at room tempature. If it is testing open or the ohm reading is way off then you will need to replace the tempature probe. If it is testing good then it could be aproblem with the control board.

either you have a bad wiring prolem or you need new gadges