1998 K1500 engine light

My "Service Engine Soon" light came on last week. Code checked at Autozone revealed PO442. In addition, I noticed that the engine temperature needle does not come to midrange as it use to (reads around 160F versus midrange of 210F). Anyone with similar experience or history? Thanks

What engine do you have? How many miles do you have? I have a 97 5.7 which has a 180 stat in it, or is it 160, anyway 210 sounds too hot, I don't have my code reader in front of me(buddy is using), so I cant tell you what PO442 means, yet, but 160 on the gauge sounds good.

It's a 350 ci with 130,000 miles on it. The 210F is around the midpoint of the gauge and it has read there for as long as I have had the truck until recently. Thanks

First, that truck was equipped with a 195 degree thermostat....210 would be considered normal operating temperature..If you are only geting to 160, I would check the thermostat for being stuck open.
P0442 is for a small leak in the EVAP system..could be caused by a loose gas cap or some other leak, the only way to know for sure is have the EVAP system tested.

I installed a hypertech 160 PowerStat, I guess that's why mine runs where it does. I didn't know that the oem was 195. I get plenty of heat, could I do damage running the 160, HyperTech also offers a 180, for colder climates, but like I said I get plenty of heat.

Hello Unger.
If your motor is running at the optimum temperature than you could be robbing self of fuel milage and it is harder on the motor.

There seems to be multiple things going on here. My 1998 5.7L temp gauge has never gotten any higher than the first line. The center position is about 210 F, the far right is 260 F, and the gauge is logarithmic, so I'm assuming the first line is about 180. While it's POSSIBLE that a new thermostat might make my engine run a bit hotter, I see no reason to mess with it, since it has run exactly the same way for 70,000 miles (it has 110,000 on it, but I bought it with 40,000 on it).
I also get good heat in the winter.

In your case, since the temp gauge has CHANGED its behavior, the first thing I would check is to make sure the coolant is full. The second thing would absolutely be a bad thermostat. They notoriously stick open, causing the engine to run cooler than normal.

Second thing: The PO442 code and the SES light, as you know, is an "evap leak - minor". I've gone through this myself. Lots of people say "It's a loose or faulty gas cap." Well, in my state, part of the emission test during inspection is to remove and pressure test the gas cap. Since mine had just passed, I figured that was unlikely to be the problem.

BUT, check the steel surface on the filler neck where you screw the gas cap on. On my truck, it was rough, had surface rust, and was leaving cruddy rusty deposits on the rubber gasket inside the gas cap. I sanded the surface of the filler neck with several grades of sandpaper, starting with 100 grit to take off the really bad bumps, and working all the way down to 400 grit to make it nice and smooth. Then, I sprayed some WD 40 on the rubber cap gasket, and wiped and wiped and WIPED all the crud off with paper towels.

I had been getting PO440 codes about every 3-4 days. Once I did this, all the problems stopped. About 2 months later, I had to repeat the process, only this time, I was even more diligent about polishing and cleaning everything. I also put a light coat of grease on the filler neck end. It's been, I'm guessing, a year and the problem has not returned.

The factory puts a 195degree thermostat in your truck.
And for a good reason besides keeping you warm in the winter when it gets 20 below 0.
When you go redoing it with a 160 or 180 you are going to mess up the hole ball of wax.
A engine needs to run at 195 -200 degrees for the computer system to work right and provide the right fuel mix for the best gas mileage.
Also if it does not run at the right tempture it will start sludging up the oil and deluteing it down with gas.
It has to run at 195 degrees to burn the water condensation out of the oil.
So do not mess around with mother nature and your engineers design.
If you do you you will be buying another engine sooner than you should be.
:grinyes:
MT