SERVICE ENGINE SOON light
 

2003 LW 300 V6....have owned it for 4 years. Every winter we are plagued with this SERVICE ENGINE SOON light that comes on on cold days only (30 deg. or below). I go to Auto Zone and they check it and it says something like "Engine Coolant Differential Temp. abnormal" (May be slightly different wording but it pertains to an engine coolant system differential temp.)
I disconnect the battery for a few minutes, reconnect and the light stays off until the next cold spell. After so many times, this becomes a pain.

From all indications, the thermostat works like it should. (Engine never overheats in hot weather and heater warms up normally in cold weather.) Antifreeze in good shape, coolant level good.

Has anyone had this problem or does anyone know how to solve it?? All help appreciated!

ETCS ? Clearing a code does not fix the problem.

Thanks for your reply. I understand that clearing a code doesn't fix the problem. I am asking if anyone knows what the problem is......so I can fix it.:)

Get the Pxxx code (get it read again) and post that code here and we'll try to help you sort it out.

Thanks derf! As I mentioned, the light only comes on in cold weather and I'm in Texas so I'll have to wait for the next front which should be Sunday. If the light comes on I'll run to Auto Zone and get the code Monday. Appreciate it!

It does sound like the ETCS.......If it is, get it from the dealer.

Scuse my ignorance but what would the ETCS be? I'm gonna guess something elecronic and expensive???

derf, found a previous Auto Zone printout for this condition and the code is P0128 Engine coolant temperature below thermostat-regulated temperature. (The light is reset now but when it turns cold in a day or two will surely come in.) Thanks for your help!

from my limited check across the world wide web, this is a thermostat problem. Others report that their radiator cooling fans run constantly when the check engine light comes on with this code. One poster even mentioned that cold weather seemed to aggravate it and cause the code to appear.

Remedy is to replace thermostat based on what I've read.

The internet is full of information as is this site.
ETCS = Engine Coolant Temperature Sensor.