If code 51 refers to engine coolant temperature, the answer is yes. If you don't have a good electrical connection between the body of the sensor and the intake manifold, you'll get either no reading (most likely) or a bad reading.Don't mean to hijack this thread, but are you guys refering to the ECT sensor? If so, could too much tape on the threads cause a code 51?
You know, I am completely wrong. I am talking about the temp sender, not the ECT. Thanks for the catch.All the ECT sensors I have seen have plastic bodies... no grounding common to the intake.
You don't need to put any sealant on the threads. I never have, and I've never had a leak at the ECT.