Had a similar issue years ago in a Taurus. It was a bad PCM.
If the coolant temp as read by the pcm is always that high, even when cold, it's like the temp sensor circuit is shorted.
Also, hope you didnt disconnect/reconnect the pcm with the battery connected; that can cause issues sometimes (ie, can damage the pcm).
If you're able to read the coolant temp signal from the pcm, turn the key on, read it, then turn key off. Get a 33k ohm resistor (1/4 or 1/2 or 1/8 watt), disconnect the coolant sensor in the t-stat housing, place the resistor into the sensor connector, harness-side, using the resistor to act as the sensor. Leave the conenctor unplugged, turn the key on, see if the temp drops to around 80-100 degrees. If it drops, the temp sensor is bad or wrong; if it stays the same, you have a wiring issue or pcm problem.
If the coolant temp as read by the pcm is always that high, even when cold, it's like the temp sensor circuit is shorted.
Also, hope you didnt disconnect/reconnect the pcm with the battery connected; that can cause issues sometimes (ie, can damage the pcm).
If you're able to read the coolant temp signal from the pcm, turn the key on, read it, then turn key off. Get a 33k ohm resistor (1/4 or 1/2 or 1/8 watt), disconnect the coolant sensor in the t-stat housing, place the resistor into the sensor connector, harness-side, using the resistor to act as the sensor. Leave the conenctor unplugged, turn the key on, see if the temp drops to around 80-100 degrees. If it drops, the temp sensor is bad or wrong; if it stays the same, you have a wiring issue or pcm problem.
