Ok I'll try changing the sensor....also when the service Eng light come on the ten gauge pegged on hot and the oil temp light come on, but if I turn the truck off and restart it the temp is back to where it useally runs at and oil temp light went off. Also when the service light come on my AC quit blow in cold air. It only blows hot air now. Could this code and sensor be the cause of that to?
And now its get in to where it do sent want to start..it will turn over but won't fire. I was told it may be the fuel pump so I check the fuel pressure and it was at 30 lbs. Tho when I turn the key on with out cranking it I can hear the pump kick on. Should I replace the fuel pump anyway?.
No, please don't run on a guess and a hope trying to get lucky.
You started with a 1299 code.
Don't know if there are additional issues related or not at this point.
Now that it won't start, this takes precidence over the 1299 code.
If you saw 30 psi fuel pressure and hear the pump running at key on, there is no use in going to the expense and hassle changing something that won't help.
What year and motor do you have?
Are you equipped wth Pats that may be causing the no start.
Is there a coded key that may be a cause?
You have to get close to the problem before changing parts unless there is no other cause.
I had the same problem on my 2000 F-250 5.4 V8 over the winter. I thought it was because I had my plow up high and it caused an air flow restriction. But I have kept the plow high before and it never happend. I checked the fan clutch and that seemed loose so I replaced it.
Today while towing my trailer in 90 degree temperatures, the the gauge went to H and the check engine and high temp light came on. I turned off the truck, started it back up and the temperature was WNL.
So tonight I replaced the cylinder head temperature sensor and washed out the front of the radiator and we will see what happens.
I am interested to see if anyone else has any other suggestions.
GOT THE SAME PROBLEM, 03 5.4L OVERHEATS SHUT OFF, TURN ON GOES BACK NORMAL. IF THE HEATER IS ON THE HEAT GOES AWAY OR AC. WHEN I CYCLE THE KEY ALL IS WELL. GET THE SAME CODE. MY MECHASNIC HAS BLOCK TESTED, FLUSHED, THERMOSTATE, AND NEW FAN CLUTCH. THIS HAS BEEN GOING ON FOR 2 WEEKS. ANY HELP WILL BE GREAT.
On the 1299 code, use a scanner to verify the head temperature is actually over the limit.
If the sensor has been changed and the code still persists, look a the possibility a harness short or cross could be doing it.
When this code is present, the motor should be in Limp mode and run poorly by intent.
A real over heat conditon does not clear with just igniton cycling.
Over 230 degrees.
At about 230 the reistance of the sensor is normally about 1520 ohms and signal voltage is about 3.07 volts.
As the temp goes up the resistance drops as well as the voltage.
This causes the program to begin dropping cylinders by cutting fuel off in an attempt to pass cooling air through the engine.
That's within expected operating temperature range.
If you still get the 1299 code, it's a faulty sensor or wiring that is signaling the PCM to go into limp mode.
The temp range depends on several factors.
The ambient temp.
How fast your driving.
Load on the motor.
Transmission heat loading.
Age or operating activity of the thermostat.
Cap sealing pressure etc.
Here is a recent experience: I don't normally monitor CHT but did so one day while waiting for the 'boss'.
Saw 185 and rangeing between 182 and 186 during cold weather. Don't know how long it had been runnng cooler
The truck had good torque at those temps.
Finally got around to change to a new 195 thermostat.
Inital warmup went as high as 220 before suddenly opening up.
My digital monitor updates every 2 degrees change.
Now the temp ranges between 194 and 200 at extremes.
Engine still has good torque, fuel mileage has gone up a bit and the EGR operating range is now a bit different.
Overall an improvement just from moving the operating up an average of 10 degrees.
BTW, the health of the system was astondingly clean when changing the thermostat so the old original stat just go tired after 170k miles.
Can't prove it but I put a larger capacity radiator in years back when towing heavy loads, for extra cooling.
This extra capacity would tend to make the thermostat open and close somewhat more often to maintain average engine temperature.
I would guess your cold starting would suffer somewhat with your 1299 condition as well as telling the PCM a false indication.
The CHT is part of the cold start stratigy because it's the only way the PCM has to know it's going to be a cold start.
This is a major part of setting the fuel injection level and ignition timing along with input from the IAT.
If you have not changed out the stat, for the cost, I would do it trying to hit a 195 average operating temp and pay attention to the amount of contamination and maybe do a flush if needed, then refill with 50/50 mix.
Pay attention to how much heat you can get from the heater as possible indication of a problem.
Once you have it running at the average temp, let it cool to the next day and see if there is any vacuum in the bottle when the cap seal is broken.
If not replace the cap.
The system depends on operating at a pressure in order to raise the boiling point of the coolant so the cap plays a very important role for both pressure and vacuum holdings in the closed system.
So today, my high temperature light came on. This time I had my scan tool on and saw the temperature. The coolant temperature was over 250 degrees. I was able to slow down, get the temperature back to around 220, turn off the truck and get the light to come off.
The things I have done to far to fix the problem with no results:
Change Cylinder head sensor
Oil change and filter
New fan and fan clutch
Tested the thermostat and working properly
You have the radiator and water pump left to be the cause.
I would go after the radiator next.
If the bottom quarter is plugged, the cooling capacity will be restricted.
Often the tell tale sign is the draining is slow or absent and dirty when opened up all the way.
Without the scanner you would not have known what was happening.
Not that it helps you, I have a perfectly good stock radiator I took out at 35,000 miles and replaced with a high capacity unit when I was towing very high gross combined weights.
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