Service Engine Soon Light

[DirtySanchito]

I recently drove home to Illinois from California on leave, and when i was driving through Arizona my service engine soon light came on. The car was running fine, idles fine, the RPM's never jumps up or down, but the only thing I noticed was that the engine is running EXTREMELY cold. Normally while driving in California, it is normally halfway between cold and hot, which is where it is supposed to be, but when I filled up in Arizona, and I started up the truck, the thermometer read at the line right above cold and never heated back up. Now I am in Illinois and it is still reading cold. Anyone have any idea on what it is so I know what to get replaced or should I take it to the shop and just have them find out what is wrong? Anything will help! Thanks!

 

[DirtySanchito]

I would take it to AutoZone to have them find out the codes, but the closest AutoZone is 30 miles away, and I don't want to drive it anymore than I have to if there is something is seriously wrong with it.

 

[Exproblems]

I recently drove home to Illinois from California on leave, and when i was driving through Arizona my service engine soon light came on. The car was running fine, idles fine, the RPM's never jumps up or down, but the only thing I noticed was that the engine is running EXTREMELY cold. Normally while driving in California, it is normally halfway between cold and hot, which is where it is supposed to be, but when I filled up in Arizona, and I started up the truck, the thermometer read at the line right above cold and never heated back up. Now I am in Illinois and it is still reading cold. Anyone have any idea on what it is so I know what to get replaced or should I take it to the shop and just have them find out what is wrong? Anything will help! Thanks!

>>>>>>>>>>>>>

Best thing to do is find out what the CEL code is for starters. If your vehicle ran okay after you noticed the CEL come on, it "might" just be the temp sensor or dash gauge went bad. Make sure your coolant level is full just to be sure, and see if you get heat through the heater core and into the vehicle as you should. If it isn't running hot or over heating, I wouldn't be too worried about it, probably something simple to fix. Generally, when a cooling system fails, the engine overheats like from a stuck closed thermostat that never opens and allows coolant to flow thru the engine and heater core, thus causing the engine to overheat. Also, a loss of coolant from a leak, blocked up radiator core etc. can cause a vehicle to overheat, but I don't know of anything that can cause a seemingly fine, running engine to run "cooler" than it normally would all of a sudden. Maybe I'm wrong but I can't think of anything that would do that, run cooler, other than a faulty temp sensor reading. Do you know if it ran hot or overheated on the drive home? Take your vehicle to the cheapest place to get that CEL code, the 30 mile drive to Autozone or your nearest auto repair shop with a code reader. The 30 mile ride would be the cheapest I would think, Autozone checks CEL's for free, and you could buy any parts your might need while you are there. Kill 2 birds with 1 stone.

 

[abarkl]

It's most likely a bad thermostat and easy to change.

 

[matt0248]

I stuck open t-stat can cause a CEL. IF it takes too long for the engine to warm up it can set a CEL. THis also generally cause a cooler running engine since coolant is flowing through the radiator at all times.

 

[Exproblems]

I stuck open t-stat can cause a CEL. IF it takes too long for the engine to warm up it can set a CEL. THis also generally cause a cooler running engine since coolant is flowing through the radiator at all times.

>>>>>>>>>>>>>>>>>>>>>

I know a stuck open t-stat will take longer for an engine to warm up initially from a cold start, but once the engine warms up to operating temp as you dirve it, doesn't the t-stat stay in the open position the entire time after that while the engine stays running? I'm under the impression they stay open, not that they open and close periodically while the engine runs. In all the vehicles I have ever owned, once my engine has warmed up and the thermostat opened at normal operating temp, my temp gauge needle never moves from it's normal temp range. I know thermostats are set to initially open at a certain temp like 195 degrees right after start up, but if they closed again and blocked coolant flow while the engine was still running, wouldn't the temp gauge needle jump up to a hotter temp reading till it opened again and allowed more coolant flow thru the system and cool it down again? I thought once the t-stat opens, it stays open while the engine continues to run.

 

[matt0248]

A T-stat is not an open/closed switch, where it is either fully open or fully closed. It gradually opens and closes to regulate the temperature. If it is stuck open and someone is driving down the highway with a fully open T-stat it is possible for the engine temp to significantly drop. Because the OP was drive from CAli to Ill I can only assume they were on the highways going 70 MPH wich would have a ton of airflow across the radiator to cool the coolant down.

 

[Exproblems]

A T-stat is not an open/closed switch, where it is either fully open or fully closed. It gradually opens and closes to regulate the temperature. If it is stuck open and someone is driving down the highway with a fully open T-stat it is possible for the engine temp to significantly drop. Because the OP was drive from CAli to Ill I can only assume they were on the highways going 70 MPH wich would have a ton of airflow across the radiator to cool the coolant down.

>>>>>>>>>>>>

I know t-stats aren't "switches", and I knew they gradually opened as the coolant temp rises in the engine from a cold start. I just thought once they were opened and up to operating temp, they stayed open unless you shutoff the engine, then they would close again as the coolant cooled off below their operating temp. Thanks for the info though.

 

[DirtySanchito]

Thanks guys, I went and talked to a mechanic and told him what was going on and that I thought it was the thermostat, and the mechanic said that the thermostat was stuck and to replace it would be really easy, so I did that and now the temp is right where it should be. so thanks for all the help!