OK ladies and gents I really need some help.

My temp gauge goes from below normal to pegged instantly and the engine is not overheating. I've checked both temp sensors on the manifold and both connectors, they are fine. I've replaced the thermostat. The head gasket is not leaking, antifreeze level is fine, stays full. When the temp pegs the overheat light comes on then a couple min later the engine starts powering down (shutting down cylinders overheat mode). If I turn off the engine and restart it goes back to normal then repeats minutes later. If I turn off, then unplug both both sensors the temp gauge pegs again but does not cut off engine and will run fine. I have ran it 300 miles like that will no problems. I just can not stand not having a temp gauge. I'm pretty sure it is an electrical problem or computer problem.

Has anyone ran into this problem, any solutions. Yes I know get a aftermarket temp gauge and don't worry about it, but I don't want to stare at an overheat light forever. Is there anyway to shut this temp gauge off without shutting down the entire dash??

 

First thing is to scan for codes set when the condition exists.
This will give a clue to the issue and what to do about it.
The dash gage and lamp is only reporting the fault
Fix the cause and the dash actions will go away..

 

Thanks, there is no check engine light on will a scanner still read it?

 

If your sure the motor is not overheating then all the cooling system work was unproductive.
Seems like only the coolant gage circuit is in trouble.
If you have the full electronic dash, it has it's own micro processor that runs all the functions with inputs from the PCM and some individual sensors.
The CHT will be monitord by the PCM . If there is an issue there, then the PCM will react to it seperately.
No codes would indicate only the dash indicator circuit is in trouble.
You just have to sort and seperate where the real fault is.

 

I am having a similar issue with my 197 f150 4x4 4.6L. I was having gauge issues (Oil pressure and voltage). I swapped out the oil pressure switch and found I had a bad ground. Anyways, upon restart those two were fixed but the temp gauge was pegged. UGH!

I replaced both the temp switch and the coolant temp switch, still not fixed. If I pull the plug the gauge reads Cold., If I short the temp connector it reads hot. The factory service manual says it is a switch issue... tried 2 new ones no luck.

any ideas?

 

I should add that I get no codes...just a temp gauge pegged to hot. This is on a cold engine too.

 

I finally fixed mine there is a total of 3 sensors 2 on top of the manifold and 1 underneath the manifold. u can access it by removing the alternator and reaching into the valley under it. It can he done cause this is how I replaced mine if standing in front of the truck facing the engine it will be on the front right side

 

is that third sensor visible once the alternator is removed? I'mhaving that exact same problem.

 

On a 97, there are only two sensors.
One is for the computer to read head coolant temperatures for cold starting and running temps.
It has no connection to the dash and can set a code if the circuit is in trouble or the sensors detects an overheating condition.
The other coolant sensor drives the dash. It will not set a code because it's not part of the engine control system.
In later years, one sensor was used for both functions.
Good luck.

 

Yeah im not getting any codes. From another thread i was reading about my sensors i saw that the temp gauge not working could be causing my other problem which is my o2 and ho2 sensors are not ready for smog no matter how much i drive. does this sound right

 

No.
The system is defined by design as separate functions monitored by self diagnostics that drive related codes.
There is to much guessing based on lack of knowledge about how the control system works in total.
This lead to things like what you read, that are not correct.
There are 7 separate system tests that are done by the computer.
If one is not test complete, a code 1000 is set. There will only be a code for that system if a fault was found.
If one does not complete there is a report which one it is and the test conditions to enter that test was not present to even begin the diagnostics.
This is what has to be looked at deeper because there is no code for not entering a test, only for a fault detected during a test.
The separate subsystems rarely affect each other directly.
This auto control system is one that hardly ever makes a mistake because it can't by design and cannot afford to given the application..
Everyone must understand these are LOGIC systems.
There is no guessing in a logic system. The Logic is a yes or no, nothing in between but a possible intermittent failure that is still positive reporting either way.
Good luck.
.

 

I am having exact same problem ,1999, F150 with a 4.2. Was yours a 4.2 as well? I'm wondering if I havevtgecsamec3 sensors, I want aware if I do. Also , when mine does it,, it does set a cylinder head overheated code.... any ideas or suggestions?

 

The thread starter hasn't posted in 10 years.

 

Some 4.2L engines have two sensors, some have one.
A change was made about 1999 to one sensor.
If the computer is reacting to the sensor change in resistance, it will trigger the LIMP mode by design to protect the engine and set the appropriate code besides pegging the dash gauge.
This would suggest the sensor circuit is working as intended.
The first thought is there air in the system for some reason?
Maybe a cold leak.
Pay attention to the Reservoir level going down. Is there a Vacuum in the Reservoir when the engine is "completely cold". There should be an indication when the cap is slowly removed , you should hear the Hiss of air rushing in. Is the Cap faulty?
A Sensor suspended in air or uncovered by coolant or an air block will not be able to register temperature correctly..
A blocked radiator at it's bottom will have less cooling capacity.
Also the oil pressure sensor may be connected into the coolant circuit.
The reason is, either failure can damage the engine, so needs to be seen for the same reason.
A short to ground in the harness will peg the dash gauge, as well.
Good luck.
.

 

He had to find this thread no matter how old it is by searching and these things come up.
He says he has the same issue.
Why is in not appropriate to answer the question 10 years later?
I have, at times, searched for an answer to a question and had my own answer come up from a long time ago on various forums and chuckle about it.
I offered an answer the 10 year OP very likely would never replay to.
He may not even own his truck by now.
This is the present posters first post.
Ya know, even if a thread poster 'dies', his life does on a long time in history.
Hope this will be a consideration for the future.
Forgive me for taking a different view.