1998 three wire coolant temp sensor issue
Thread Starter
Teching In
Joined: Oct 2014
Posts: 6
Likes: 1
From: Wichita Falls, TX
1998 three wire coolant temp sensor issue I swapped a 98 LS1 into my dad's 240z and we started it for the first time the other day.
Question up front. Why would the temp sensor always show 70F at all times? It does this with the sensor connected and disconnected. I bought a new sensor and hit it with a heat gun (while plugged in) and no temperature change viewed through VCM scanner with HP tuners.
I don't have the gauge wire connected to anything (aftermarket speed hut gauge is being used). Does that gauge wire need to be connected/grounded if not being used?
I have a good 5v reference and good ground wire tested at the plug.
Thanks in advance.
Question up front. Why would the temp sensor always show 70F at all times? It does this with the sensor connected and disconnected. I bought a new sensor and hit it with a heat gun (while plugged in) and no temperature change viewed through VCM scanner with HP tuners.
I don't have the gauge wire connected to anything (aftermarket speed hut gauge is being used). Does that gauge wire need to be connected/grounded if not being used?
I have a good 5v reference and good ground wire tested at the plug.
Thanks in advance.
Teching In
Joined: Jan 2021
Posts: 44
Likes: 5
You might have it wired wrong if you did any repinning, or something is pinched/ shorted as with the sensor unplugged (high resistance) the temp should indicate -40*F, and if the the yellow and brown wires going to the PCM are shorted, it'll read about 285*F. So, stuck at 70* at all times would suggest a wiring issue. Even just the yellow signal wire chaffing on metal somewhere can skew the temp reading by pulling the circuit to ground.
