if l change the knock sensor on a lexus ES 300 1993 would l have to get l programed for the dealer? this guy thatworks on cars said it would not crank if you change it. is this true?

If its the right part, theres no reason it would have to be re-programmed, the knock sensor, if it gets a vibration, changes the voltage & the comp changes the timing, there is no serial number to the sensor, no way for the comp to know if its old or new as long as its the correct part. You may want to make sure the timing is set correctly first, as the wrong timing will cause the knock sensor to ''go off'' & change it again.

You can check it by tapping the engine near the sensor with a hammer while using a timing light, the timing should jump.. If ur eng light is the only indication, the comp error *really* means that the timing is being adjusted for more than 20 sec due to the sensor, but that doesnt mean its the sensor thats bad, just a likely canidate

l do not know the specifics of a Lexus. But changing the sensor, should just be light changing a light bulb, in the sense that once its replaced, it should work again. l suggest checking a Lexus web group for more specifics.

l am a Lexus technician, and no the knock sensor does not have to be programmed in anyway. But you may want to go ahead and replace the small wiring harness that comes off the knock sensors(your vehicle has 2, one for each side of the engine), the wiring will sometimes corrode and set knock sensor codes. l assume your check engine light is on, you can clear it by pulling the EF l fuse.