"why does the fan come on if I unplug the cts harness from the sensor?"
Good question. It should not. With the ECTS unplugged the pcm sees a -40f degree reading. Did you closely inspect the connector for the ECTS? When the plastic tip fails it cracks. Slight amounts of coolant leek thru into the connector.
I would think that it is possible that it is shorted internally. This would read full voltage to the pcm which would then turn the fan on. Plugging it in might be undoing the short.
Also double check the ground to the fan.
The pcm and only the pcm turns the fan on.
The fan should come on from the request for the AC after about 40 seconds or so.
The fan will also come on when the pcm is in a diagnostic mode.
The pcm turns the fan on when it reads over 220f from the ECTS.
The pcm has a learning mode that it goes thru every time the battery is disconnnected. It will take a little drive and idle time for things to get back to normal. Try disconnecting the battery and then see what happens.
The vss has no input to the pcm for the cooing fan.
G luck and let us know. :)
Tuesday, March 13th, 2007 AT 3:00 PM