Diagnostic fault codes never say to replace parts or that they're bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. Code 2074 just indicates the two sensors don't agree, but it doesn't say why. For example, one might say you're at wide-open-throttle while the other one says you're under light load. Those two conditions don't agree, and that is what must be diagnosed.
To add to the problem, no two sensors are ever exactly alike. The Engine Computer had learned "minimum throttle" from the old throttle position sensor, and any time it saw that signal voltage, it knew your foot was off the accelerator pedal and it had to be in control of idle speed. If the lowest voltage your new sensor ever reaches is just.01 volt higher than that of the old sensor, the computer will never see that voltage that tells it to maintain idle speed. Until you meet the conditions for the relearn to take place, the engine may be hard to start unless you hold the accelerator pedal down 1/4", you won't get the nice "idle flare-up" to 1500 rpm at start-up, and the engine will tend to stall at stop signs. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.
This idle problem is in addition to whatever was the original problem. A good place to start looking is to follow the smaller positive battery wire to the under-hood fuse box, and be sure that connection is clean and tight. Follow the smaller negative battery wire to the body and be sure that one is tight and not rusty. The next suspect would be overheated contacts inside the ignition switch, and the terminals in its connector.
Tuesday, June 16th, 2015 AT 7:12 PM