Difficulty getting up to temp for TDCO learn

[jdmetcalf57]

I recently replaced my IP & got a Carcode scan tool to set the TDC offset learn. I could not get the carcode to tell me it was upto the 170 deg it needs to to do the learn procedure even driving it around. Finally I clamped the radiator hose off completely then I got it there.
With all of this and driving it around even pulling a trailer it never gets over 164 deg. The actual gage gets about 195 deg which seems correct for the thermostats. Does anybody else have this difference between the computer temperature and the gage? Is it normal? Would it cause any other problems like reduced performance with the computer not thinking the engine is fully up to temp?
I am thinking I may need to replace the ecm sensor. Does anyone agree?

[Robyn]

Sounds like the "Coolant temp sensor" which is mounted in the coolant crossover is faulty. (Easy fix)

The gauge sender is in the LH cyl head near the front right ahead of the exhaust manifold.


I was not aware that the Carcode scan tools could do a TDC Learn procedure

Which model tool???

[jdmetcalf57]

The basic carcode package will work. There are other threads that are very specific about how to do it.

[jdmetcalf57]

I replaced the sensor then the computer pretty much agreed with the gage. The old one read about 25 deg cooler. The GM service manual troubleshooting guide did not even discuss that the sensor may be off just if it was completely high or low. It has been that way for a long time. It runs a lot better now. It seems to be getting better mpg now. I wonder how many thousands of dollars I wasted in fuel over a $20 dollar sensor.

[Robyn]

If that sensor is not feeding the correct data, then the ECM can't really adjust the fuel and timing correctly.

Yup, it likely cost some $$$

More than likely it was not a huge amount, but overall performance should be better now