Of course, that might not get you caught in NY (don't you have emissions testing, too?), but in CA, ya gotta have 'em. They're worth the money to a Californian! As for Check Engine Lights, they'd damned well better come on if your car's >96 (give or take a year). OBDII requires catalyst monitoring. That's why people get MILs when they take off their cats; the computer looks for phasing of the O2 sensor before and the one after the cat to make sure it's there and working. If your car is before '96, you're correct, you won't get a MIL. FYI.
just as a follow-up to this thread: 1) I bought a used cat, the old one WAS obstructed (per visual inspection) 2) According to the Ferrari tech, a marginal O2 sensor can (and often will) cause the problem, where it is not "bad enough" to turn the check engine light on (or it goes on/off periodically), but causes permament damage to the cat which accumulates over time. 3) You can read the fault codes after a check engine failures yourself. turn on the ignition, do not start the car. push the black button on the ECU box for the bank in question, keep pushed for ~10 sec. the check engine light for that side will start blinking in sequence, blink fast = count decimal digit (i.e. 4 fast blinks) pause = wait for next digit blink fast again = count next decimal digit. (done for four digits codes) for example, a code 4512 would be 4 blinks, pause, 5 blinks, pause, 1 blink, pause etc. This sequence is then repeated over. If there was more than one error, you will see a different sequence. the resulting code must be interpreted according to a table.
