128 code giving me a headache

[avalen210]

been trying to get my Sportage (2001) to pass emissions and I keep getting the 128 code (check engine light) The sport has a new radiator (6 months ago)
new water pump (3 months ago) new coolant and thermostat. Also put a new
heat sensor (little square one on the thermostat housing) The thermostat is rated for 192 which is what the specs show from AutoZone, I asked for a 195
thermostat and he said Kia doesn't give them any specs for 195. So....what
would be a part # for a thermostat that will give me a temp rating of 195.
Would another type car thermostat fit it if it was a 195?
Gotta get it to pass emissions, it runs good, doesn't smell or smoke and its not
like I'm driving a rundown wornout old car, just barely has 94,000 miles on it
and I expect it to last me at least until 200,000 miles.
I could certainly use some help sorting this problem out.

[spongebob218]

Make sure you have a perfect 50/50 coolant mix. This made a difference on the old Sportages.

Is the fan clutch working properly?

[aquanaut20]

P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

This code pertains to the sensor which sends data to the ECU, it requires >170* to permit the Computer to attempt CL (closed loop), the emission system will run in limp mode until then (poor performance/economy). AND MAY ACCELERATE THE CAT's DESTRUCTION (RUNNING RICH).

The sensor you replaced may have been the second sensor which activates the dash gauge/lite..

You need to first verify the engine temp (IR), then connect a LIVE DATA SCANNER (not a code scanner) and verify what temp the ECU is receiving.... Philip

[avalen210]

its possibly the coolant, its not 50/50, more like 75/25 figured that was better in 120 degree temps in the desert, seemed ok for summer. For now the gauge just barely comes off cold driving to work in the mornings (cool mornings, 50ish) but afternoons it runs halfway, the normal limit as the
day has warmed up to 75ish. Almost thinking the new thermostat is faulty and stuck in the open position. Will check into getting a shop to run a LIVE DATA SCANNER on it.
Thank you

[aquanaut20]

The correct method to diagnose the ECT is as follows

After the vehicle has been inactive and the coolant/engine is at ambient temp (measure with an IR thermometer)...

Connect the Live data scanner,
turn the ignition on (no start)
Read the temp for IAT (Input Air Temp)
Read the temp for ECT (engine coolant temp)
These values must be close to the ambient temp (first measurement,IR)
start engine
ECT must start to rise withing 1min,
ECT should attain >170* for PCM/ECU to go CL (closed loop) within a couple of road blocks...
Coolant must remain in the coolant spec range (180-195+) to make the ECU happy...

If the above fails, re/re thermostat..... refill (50/50 mix) and burp cooling system....

Retest to confirm repair..... Philip