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I have a 2003 Z06. I will post everything that has been done to it so far. It seems to have been to 100 shops with a 100 differant hands.
The car currently started to randomly go to redline & then back to under half with the chimes & coolant over temp continuosly until you shut it off. I disconnected the battery the first time & when I drove it again, went right off again.
I then replaced the thermostat, Ran fine for a ride, Let it idle for a while seemed fine. A day later as soon as I start it it goes straight to coolant over temp & dancing needle.
I then changed the Sensor & ran fine for 2 rides. It then proceeded to do exact same thing again.
Im hoping to actually get a definitive answer once & for all. So Frustrating.
It may be an ECT wiring issue...did you buy an OEM sensor ???...The ECT is a basic 2 wire thermistor...5 volt ref signal and a low ref (ground)...you changed the ECT but I’m guessing 100% you didn’t check the wiring...if that signal wire gets shorted to ground the ECT will peg out HIGH !!... to check you would have to disconnect the ECT connector and also whichever of the 2 PCM connectors where the low ref. resides...you would then check for a “short to ground” with an ohm meter !!..,where in NJ are you located ??
Well I found out the OP lives in my little shore town of 1.8 square miles...LOL !!...well before swinging by on Sunday if you want to “shake down”
some wiring before then at the back of your left fuel rail you’ll see this bracket...a lot of C5’s have wiring that chafes this bracket and your ECT wiring runs inside this wiring bundle !!...your yellow signal wire may be worn through at this area !!...I reinforced mine with an extra “layer of protection”...if it looks like no evidence of damage I will see you on Sunday !!...and as I had mentioned any issue with this circuit will NOT illuminate the MIL !!..see if you have a P0117H !!
OK Guys, Derek the OP brought his car by...it has a new temp sensor previously installed and wiring from sensor to the harness bundle looked fine...no DTC's stored !!….found the wire bundle chaffing against the fuel rail bracket but it didn't "look" like it went through !!...put a section of plastic wire loom around it anyway...if the issue returns I'll just have to cut the tape back and check....also checked the car ECT with scan tool on both "enhanced" and "generic" OBD2 sides...all temps agreed to the degree...did find a coolant leak from radiator so OP will be looking into that...OP was going to drive the car around and see if the issue occurs...he just texted me and said "so far so good"...if it was going to act up it would have done it by now” !!
2003 Z06 (Another Coolant Over Temp Random Issue)
