P0118 code, ECTS reading low???

[pcampey]

I hope someone here can point me in the right direction. I have a '99 SW2/ manual trans with about 100K on it. The car has been trouble free so far, however, a couple days ago it began to intermittently idle erratically, the gas mileage dropped significantly (20mpg) and the SES light came on temporarily for a single day. The SES light did not stay on the following day. I scanned the system with a Auto Xray-5000, which showed code P0118/ High input ECTS circuit. The coolant temp gauge on the car reads 1/4 from cold, which is where it has always read since day-1. The Autoxray reads the coolant temp at 141 degrees which is 50 degrees lower than it should be. Does this indicate the ECTS needs to be changed?

More background: The 195 degree thermostat was changed 6 months/ 6K miles ago The coolant and other key fluids were changed last month. The ECTS itself and wiring all look good... Thanks! pcampey

[WingsOfSaturn]

Welcome to the forum.

You did not mention that you have changed and/or verified that you have a brass ECTS. Sounds like you have a cracked plastic one in there. Also check for corrosion in the connector to the ECTS, if so replace it.

[fdryer]

If the original ects (plastic tip) is in there, REPLACE IT NOW!? All plastic tipped ects' fail hence the high resistance input (interpreted by the pcm as high resistance/low voltage/cold temperature sensed (incorrectly) leading to rich fuel mixtures as the pcm is fooled into thinking the the coolant is still cold. The temperature gauge is reflecting the error of the coolant sensor by 50F. Replace it with the brass one for the cure. Since the 195F thermostat was already replaced the only faulty part is the coolant sensor. The temperature needle will be closer to the 3/8ths mark and fuel use will drop to improve fuel economy.

[pcampey]

Thanks, That makes perfect sense. It is the stock plastic tipped ECTS. I'll order a brass sensor and change it out immediately. I'll let you know how it works out...Thanks again,pcampey