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To start off, yes, I have searched and replaced all the things that have been suggested. New ECT sensor and connector, OEM thermostat, New water pump, cleaned and sanded all body/engine grounds, cleaned pins on C180 connector.
I started getting this issue last summer while waiting on a tuning slot to open up. My 2006 has been a long term project (7 years) due to work and health unfortunately. I couldn't work on it at all over the summer and It wouldn't replicate the problem during the winter. It will only do this issue if it is over 84 degrees outside. The car only has a re-flash base tune for the injectors so I can start it and move it around currently.
To sum it up on completely cold start (sitting a day or two) it will kick the Hot Engine display and the fan will run full blast. DIC and gauge show XXX for coolant temperature. Using a OBD2 dongle and phone app I can see the coolant temp display correctly, but I am showing odd numbers on my IAT. I ohm'd out the IAT pins in my MAF and they showed 1830 ohms @ 91 degrees outside. The only code I am showing is P0116 and it is sometimes current and sometimes pending, either way if I clear the code the car will start right up without the Hot Engine issue and the DIC reads out normal (shown in pics).
Talking with some of the tuners/corvette guys in the area (DFW, TX) I am getting one of two main issues, I either have issues with my wiring harness or my PCM has an internal fault. Just seeing if theres any other opinions on here before I pull the harness and pcm.
This is the conditions which will set that DTC…your condition would be the 1st condition…by looking at your picture looks like a bad IAT or it’s ground or 5 volt reference is missing…reading -27 is as if the sensor connector is “unplugged”…the IAT 5 volt reference is pulled to ground through the IAT sensor which will give you a temp reading…you have to check for 5 volts and ground with a DVOM and test light…best to use a test light to check the ground…you may also have a bad connector either pin fitment of wiring at the connector…try a “wiggle test” on connector when reading the 5 volts or ground…see if you lose either when wiggling the connector.
This is a simple 2 wire thermistor circuit so with ignition in run (green light on) you should see 5 volts on the tan wire at end of connector and with test light hooked to B+ (alternator B+) the test light should light if ground is good…you have either a broken wire on reference ground or maybe broken wire on 5 volt reference if you don’t see 5 volts…before checking for broken wire on 5 volt reference see if you see 5 volts coming out of the ECM…I read 1564 ohms on my sensor at 90 degrees.
This is a simple 2 wire thermistor circuit so with ignition in run (green light on) you should see 5 volts on the tan wire at end of connector and with test light hooked to B+ (alternator B+) the test light should light if ground is good…you have either a broken wire on reference ground or maybe broken wire on 5 volt reference if you don’t see 5 volts…before checking for broken wire on 5 volt reference see if you see 5 volts coming out of the ECM…I read 1564 ohms on my sensor at 90 degrees.
P0116/Hot Engine, A/C Disabled issue - 2006 Base
