i am having an issue with my 2007 mazda 5 2.3L

I am due for inspection and emissions. I am 1 week past so I am trying to resolve this soon.

the check engine light has been on for a little while. the code is p0126 insufficient cooling.
three causes,
thermostat, engine coolant temp sensor, or low coolant.
I ruled out thermostat because the temp gauge moves half way between C and H after a few minutes of driving. (it takes 10 minutes for me to get to work and it heats slowly but surely. I also drive for 45 minutes recently and it never went above half way) also the radiator fan does kick on and shut off normally that I can tell.
I thought temp sensor or low coolant. I did fill the radiator a few time when the engine was cold. I was about to change the temp sensor and the light went off on its own.

now to my issue with the emissions.

2 weeks ago, I disconnected the battery to clear the check engine light.(I am sure that was not a good idea, but I did not know what else to do)
I had my wife drive a few days and I drive the rest. my wife drive it about 10 miles, about 20mins to work one way, at a high of 45mph it was various of 25/35/45mph no more than 5 minutes or each, with stops at red lights every so often.
the other days, I drive it to work, 4 miles, about 10 minutes. mostly 25mph with stop signs, and about 2-3 mins at 40mph.
we racked up about 170 miles this way. the check engine light did not come back on. I took it for an inspection/emissions on feb 1 and the emissions failed because it was Not ready for testing. they said drive some highway. at this time, I had driven about 175 miles. I then drive on the highway to Hershey park. this is about 45 minutes away from me. I drive about 70mph for 30 minutes and about 50mph for 10 minutes. on the way back from Hershey park, the check engine light came on. same code, p0126. I was going to change the temp sensor, but had to wait for Thursday, because I could only do it after work, and Thursday, we had not activities.
on Monday or Tuesday, I filled with gas. about 4.8 gallons which equaled a half a tank. I also added coolant to the radiator Sunday to the point where it overflowed. I squeezed the radiator hose to release any bubbles. after filling up the gas, I drove another 50 miles. I was going to change the temp sensor on thursay evening. I drove to my parents. about 1 mile from my house. it was still 4 miles from my work. I then drove up the hill to the grocery store, about half a mile. when I left the grocery store, the odometer read 50.2 and the check engine light when off. I did not change the temp sensor.
I drove another 20 miles and had the emissions tested to finish my inspection. the emissions failed again because it is not ready for testing.

any suggestions

should I perform another drive cycle to reset the computer? if so, what is the proper drive cycle?

anything else anyone can suggest. I feel like the temp sensor may be ok, but if I should change it, I will. the best day is Tuesday this week and Thursday.

I hope someone can help/

thanks

 

Replace the thermostat.

 

So even though it all seems good, the thermostat will resolve my issue?

Can you give me any specifics as to why? I ask because I am trying to learn more about this, so a history lesson would be appreciated.
Thanks

 

I could but it would require too much typing for no good reason. Thermostats are maintenance items. They open and close constantly in high heat/pressure. Replace it.

 

thermostat shoud cause longer "cold" condition or overheat. Overheat is primary caused by blown head gasket often. Check water pump for leak signs (colored salt maps).

Half hour driving in country shoud "clear" P1000 code. What diagnostic tool was used? (my is common ebay ELM & Forscan)

 

​​​​​​

^ what is that ^^^^


This is an old thread... but someone recently responded and it pop up as an active thread now.

First people why do you all keep disconnecting the battery to TURN OFF the check engine light without first finding the cause of its activation. You did read "TURN OFF" the light and not fixing the problem? Those DTC=Diagnostic Trouble Codes are there for a reason. This is for someone that half knows what they are doing to access the DTC using a Diagnostic tool at the OBDII diagnostic connector and reading any and all the DTCs. Then you could properly clear any DTC that experience may have you believe they might have been trigger due to a serious or singular anomalous condition. Then do at least one FULL drive cycle to see if the DTC returns> If not you can then go look at the Monitors and see if all is GREEN or READY. IF not then you know you either need to do another full drive cycle or two or further look into the issue that is causing the MONITORS to be in fault. This is where you go back to your notes you made and look at the original DTC and start your problem solving service tree to find the original cause of the DTC(s). This is time consuming and to some degree needs some experience with knowing how to use diagnostic tools and i using it correctly you will resolve the problem ! This folks is all call Diagnostic trouble shooting and resolving. THERE ARE NO SHORT CUTS to doing this kind of service!

But if you guess and start changing parts on a hunch you may inadvertently cause more issue then the original problem.

Summary: DONT DISCONNECT THE BATTERY BEFORE YOU HAVE SOLVED THE REASON FOR A CHECK ENGINE LIGHT!