Pontiac Repair: no convertor lockup, coolant temp, coolant level

Question
I have a 2001 Grand Prix GT with the 3.8 non turbo engine. The convertor is not locking up causing the engine to run at 3K rpm at highway speeds. This causes excessive fuel usage. The gauge has always shown the engine temperature in the 160/180 range. The coolant level sensor has gone bad showing low coolant all the time. Is the low coolant signal affecting the transmission or do I need to look for another issue?

Answer
Hi Paul:
I don't think I would trust the temp gauge on the car. does the car have good heat? It it has good heat I'm sure it's up to temp if not then the thermostat may be opening too soon. to answer you question Yes the coolant temp can affect the TCC engagement but even it it were say 180 degrees It should still luck up at a constant crusing speed while either in 3rd or 4 th gear. Has any service engine light come on? If the TCC were not working at all or it was slipping the service engine light will come on. A likely cause to a no TCC apply would be a break switch that's mis adjusted I think that car has 2 seperate switches just because the lapms are not on doesn't mean the engine computer is seeing a brake switch input. if it is the all in one switch it could have a bad set of contact in it causing the same things as a mis adjusted switch. Just a few ideas. Good luck :}