p1620 code

[lauriejane]

Recently topped off coolant with only 3 ounces of prestone dex cool extended life coolant (labeled mixes well with all other coolants) mixed 50/50 with distilled water, so six ounces total. I did a lot of research and most info stated it was fine to use this coolant for a top off. I ran the car for about 75 miles and everything was fine. Now, I have a code of P1620 which is usually indicative of faulty thermostat. Kind of ironic it happened only shortly after adding the coolant. Is this just coincidence, or did I totally screw something up? Advice please.

[MIKYZZ4]

For small top off amounts, diluting with water is unnecessary, perfectly safe.
I think it's just coincidence, but can I ask when was the cooling system last refreshed?
2003- so might be time-14 year old parts , if original!
If no unusual temperature fluctuations, just clear codes.
Scan again after a short drive cycle, if just to allay your fears.

[Geetarbaz]

Hi, a bit late in the day but jumping in as I have the same code with rock solid engine temp, no warning light though. Did you get this solved? My code comes back after clearing...

Cheers.