TP sensor is available seperate from the throttle body and if the tech knows what they are doing they can test the resistance of the sensor and replace if needed.
Yes bad coils can interfere with ETC signals, i have replaced many bad coils, that have anbnormal RF patters, wich can also be tested by the dealer. Its not the coil thats neccesarly bad, it can still function normally but it just produces an abnorm RF frequency that makes the PCM go bonkers. It can be more than just cylinder #4 the dealer can stress test all the coils and all the bad ones should be replaced.
it all depends on what codes are set.
2107 and 2110 probably a bad coil.
2106 and 2135 (not sure on the second one) bad tp sensor and pcm reflash
Jay