I changed out the old coolant sensor on my 2003 Baja and the car will not start now after replacing the new sensor. A couple months ago we pulled the engine to repair the heads and when reconnecting the electrical portion of the engine my buddy and I put the coolant plug on but apparently not on all the way because until we removed it and plugged it again the car would not start. After changing this part yesterday the car will not start. Does anyone have any ideas, it has to be this plug some how, I took the new part back and replaced it again and also put the old part back in and tried it again with the same result. Does anyone know how to trick this plug? Or prove that it is the plug?

Perhaps there is a loose harness or hose. The car would run without the temp sensor connected. If the fans default on all time, this would be the case. Otherwise, check the engine harness connections on the bellhousing for loose pins or wires pulled out of the plug. Check all the PCV hoses runningt ot he bottom of the iarbox.

you can check continuity between the CTS connector and the main engine harnesses plugs at the rear passengers side of the engine. 

FSM will show which pins are for the CTS. 

 

or - even simpler - just put one multimeter probe on the CTS connector wire - then touch every single pin in the engine harness connector.  one of them should complete the circuit.

I re-checked all the hoses and connectors to make sure everything was still connected. The funny thing about it is, its an easy change, its two electrical connectors and the air box. You do have to move a couple of electrical connections so I disconnected and reconnected those with no luck. Question: CTS connector? on the engine harness what color is it, I can dig into that and check continuity there.

i don't know.  have to find the FSM or just test them all - only takes a second to touch each pin.  should find continutity there - then maesure it's resistance.