The coolant sensor is towards the back of the engine on the driver's side. To reach it you will have to remove the Intake manifold cross-over pipe. Once the cross over pipe is removed its easy to get to the sensor. The sensor has 4 wires. If I remember correctly the plug to it is a Molded plug, which I somehow opened. Once I opened it I discovered that the wired were shorted. Somehow I managed to fix the wires and put everything back. I also remember that although it has 4 wired, 2 of the wires are ground, so I just joined them together. My coolant sensor itself was also defective, so I changed it as well.

One circuit (2 wires) of the coolant sensor serves the EGR system and the Over-voltage protection relay, The other circuit (the other 2 wires) serve the dashboard temperature gage. In my case the dashboard portion of the coolant sensor was fine, but the EGR/Over-voltage relay circuit was screwed-up, and that was the circuit that caused of my high idle speed.

NOTE: The orientation of the plug is critical, yet it is round and will plug back in several ways. Make sure that you remember how it was plugged and wired so that you can put it back the way it was.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]