shadetreewanab

I was doing some top end head work on our 2004 Mustang 3.9L V6 this weekend. In the process I broke the wire (single wire, white with red strip) from temp sensor to the harness. I spliced the wires back together.

Now when you turn the key on the temp sensor comes up like it works. When you start the car it stays up for about 30 seconds then the gauge needle drops like it is not working at all. If you turn the car off and immediately start over you get the same effect.

Has anyone had this issue and can you provide any advice?

Thank you!

shadetreewanab

The problem ended up being the "Cylinder Head Temperature Sensor". This is a two wire sensor. It was broken off at the base. The check engine light was on and the code was P1289. This is the code for the cylinder head temperature sensor. After replacing it the light went off and the gauge works properly.

On a side note. This sensor is very difficult to find and I had no luck from the internet in finding the location. For anyone looking it is located on the back drivers side of the engine block near the firewall. It is also difficult to get to. A 19mm ratcheting wrench is the right tool.