Rep Power: 0

I have a 2003 Civic with 195K miles, I started getting the P0128 code. I replaced the thermostat with a Honda OEM thermo, and now I am still getting it. All coolant levels look OK and I am using 50/50 blue antifreeze. Also just had the radiator replaced a few months ago, but code just started a few days ago, not sure if anything is related. Here is some of the freeze frame data from the code, not sure if this helps but maybe somebody knows. Any ideas what else this could be?

LOAD_PCT(%)=88.2
ECT = 86F
SHRTFT1(%)=0.0
LONGFT1(%)=5.5
MAP(psi)=13.1
RPM=2715
VSS(mph)=23
IAT=57F
TP(%)=32.9

Thanks!

 
Rep Power: 518

I'd probably want to check if this sensor is actually accurate. You sure that wasn't 86*C instead of F?


P0128 sets when the computer thinks it's taken too long to reach operating temperature. Typically that happens when the thermostat sticks open (or similar fault), but what if this ECT sensor isn't accurate? What do you think the computer might do?

 
Rep Power: 133

Do you have other DTC codes other than P0128?
Since you had the radiator replaced recently, I would check for poor or loose connections at the radiator fan sensor and the PCM. Also check the radiator fan circuit, the radiator fan switch circuit and the radiator fan switch. You already covered the thermostat with the replacement OEM Honda thermostat.
Finally could be a faulty PCM.