dctaz37

Recently my check engine light came on. I have a reader that hooks up to a laptop. I didn't write down the exact error but something like, General-Drive Train-Thermostat -Coolant temp lower than circulating temp. I reset the code and it was good for a week then came back on. the temperature gauge is normal. I would think to replace the thermostat but the temp gauge is normal. Any help would be appreciated. Car has 216,000 km.

holmesnmanny

does it take longer than normal to warm up ?

ZeroSix

Don't trust the stock gauge. In most cases, they are not linear at all and have a dead zone. Just because it is showing in the 'normal' spot does not mean full operating temperature has been reached.

Assuming your code is P0128 (verify?), either the thermo or the ECT is toast. Thermostat is easy to test. Why not start with that?

dctaz37

Yes the code is P0128. I downloaded instructions to test if it is heating up properly so I'm going to try that. It doesn't seem to take longer to warm up. What is the ECM? I'm assuming sensors and if yes where would they be and how do you tell if they are bad?

ZeroSix

I'm assuming by ECM you mean ECT? ECM is the Engine Control Module, which thankfully does not apply in this case.

The ECT, on the other hand, is the Engine Coolant Temperature sensor. These are also very easy to replace, and you don't need to buy an OEM part to replace it if need be; I run a Beck Arnley switch in my Civic and it has been problem free for years.

Report back on your thermostat test, then worry about replacing the ECT. The worst thing you can do is just throw parts at a car. Diagnose and solve!

dctaz37

I did some troubleshooting this am. The top hose gets hot after 10 min. and the bottom hose gets hot after 15 min. I'm not sure what to do next or what this tells me.

ZeroSix

10 minutes of... idling? city driving? WOT? Be scientific and specific. To answer your question: not much.

Did you determine the health of your thermostat? Stay focused.

dctaz37

I started the car in the driveway so it was at idle, held both the upper and lower rad hoses. The top hose gets hot after 10 min. and the bottom hose gets hot after 15 min. I thought this test would help to determine if I should change the thermostat or not.

ZeroSix

While your heart is in the right place, this isn't that great of a way to diagnose a faulty thermostat. Here's a snapshot from the FSM for my Civic; the technique for testing is the same for your Accord. You don't really have to suspend the thermostat if you don't have the supplies for it. Simply lay it on its side in the pan, and monitor the wax/spring for expansion while keeping an eye on the water temperature.

dctaz37

If I need to take it apart to test the thermostat, I might as well just replace it for the price, I thought I could determine if it was the issue without disassembly.

ZeroSix

Sometimes you have to get your hands dirty to solve problems. You are working on your car, after all.

I'm not sure I understand your logic. Taking the thermostat out and testing it is free, replacing it is not. However, if you feel that is the best choice, it's your money and you're welcome to do with it as you please.

dctaz37

I'd actually like to troubleshoot and determine the problem without taking it apart. Not afraid to get my hands dirty but why open it up if you don't have to.I downloaded troubleshooting steps https://www.yourmechanic.com/article...e-by-evan-clay . Now from what I have found so far I think the thermostat is behaving properly, just wanted some feedback from here to see if this is correct. Next I was going to test the ECT.

ZeroSix

If you would prefer to test the ECT first, that's entirely up to you and isn't a bad idea. Usually the thermo is the issue (apparently 'yourmechanic' feels the same way) but it can't hurt to check the ECT.

Best of luck and report back after running your tests.

dctaz37

Here is an update: I was going to test the ECT but the check engine light has gone off and hasn't returned.