Was getting an occasional code 22 (TPS low) - not constant but light would come on occasionally usually when I could not put a meter on it. MPG was also down and it would give an occasional fast idle. TCC was not always locking but had put down to around town driving rarely reaching 50. Had the scan tool on several times and in the garage everything always worked properly.

Finally got around to putting a new TPS module on (actually a spare from a "parts" engine) and after adjusting (you loosen the two screws and rock the entire module). It is running much better - now getting proper lockup in 3rd and 4th and idle is 700 rpm instead of an occasional 1250.

I *suspect* that a problem must be present for some period of time before a code sets - if the sensor is going through a fail/work cycle fairly often, it may be wrong most of the time but not set a code.

Have seen O2 sensors that were quite far off without setting a code so they need to be treated as indicators only.

Note: the two TPS screws are quite difficult to get on with a screwdriver if the manifolds are in place. I wound up loosening/tightening with a needle-nosed vice-grip for the first/last 1/3 turn.