I have a 2000 3.9 Dakota, replaced temp sensor had a code of P0118 and still have the check engine light on and the code is still there. Any suggestions....Thank you

 

did you clear the code after replacing the sensor?

 

Yes I did.

 

And it came instantly back? I think at that point there, it could be a couple things, bad sensor (out of box), bad ground or signal wire from either the sensor or PCM..

First, if you have access to a scan tool, check the reading of the coolant sensor. Does it read a logical number? If so, the problem is likely intermittent. Perform a "wiggle" test by wiggling the connector and harness to the sensor while watching the reading on the scan tool. Watch for any drop-outs. Drop-outs would indicate a bad connection. If the scan tool reads an illogical temperature, check the resistance of the temperature sensor. If it is out of specs, replace it. If it is in specifications, unplug the sensor and, using a fused jumper wire, jumper the two terminals of the connector together. The temperature reading should now be maxed out to above 250 degrees F. If not, there is likely a problem with the ground circuit or voltage supply.

I recommend getting a factory service manual to help you with the next part.
you can check here for it https://docs.google.com/leaf?id=0BzA...NjM3NGMw&hl=en


Check for 5 volts reference voltage at the connector. Also check for ground presence at the connector. If you do not have 5V ref. and/or ground continuity, check for these back at the PCM connector. If you have these at the PCM connector, then repair open or short between the PCM and the sensor. If you do not, remove the offending wire from the PCM and then check for proper voltage at the PCM pin. If it's present now, repair short on the circuit. If it isn't present after removing the wire and checking the pin, replace PCM