I have a 2000 Honda accord lx automatic. I change the timing belt and water pump. New radiator capthe heat works great and the car doesn't ouer heats. But my temperature gauge goes up to normal sometimes. But tonight I let car warm up for about 10 minutes and drove about a mile and stopped put the car in Neutral and back in drive that's when the gauge went to normal read. drove about 30 yards the gauge went back to cold. I stop again and put it in park again and the gauge went back to normal as i drove home where is stayed as i drove. Can someone help with this problem?

 

Starting with the 2000 accord, the coolant temperature is sent to the gauge in the cluster by the PCM. The PCM uses the coolant temperature sensor for the cluster and other engine controls like open/closed loop, cooling fans, etc.

Does the idle change when the gauge temperature drops? Is the check engine light turning on?

Also, do you have an OBD2 scanner that can read live data?

 

No the ideal doesn't change. Yes the engine light comes on

 

Get the codes scanned and post the code(s) on here. They start with the letter p and have four numbers, like P1234.

If you don't have a scanner, most auto parts stores will scan the codes as a free service.

 

Code is P0401 was scanned tonight.

 

P0401 is for insufficient EGR flow and has nothing to do with the coolant temperature reading. Is your accord a V6 or 4-cylinder?

To 100% verify, you would need a scanner to read the PCM data. You can get a cheap bluetooth on amazon and use a free app like torque to read engine data. If the scanner shows normal operating temperature (190-195 degrees ) and doesn't drop when the temperature gauge randomly lowers, then the issue is likely in the instrument cluster (probably the temp gauge) or the wiring from the PCM to the cluster. Depending on your DIY skills, you may be able to repair.

If your accord is a 1998/1999, then it could be the sending unit (2000+ accords don't have these). Just to be thorough, post the first 10 digits of your VIN. That should be enough to verify the year of your accord.

 

1HGCG564XY. First 10 of my Vin.

 

It is a 2000 accord that doesn't have the temperature sending unit that would only send a signal to the gauge.