mkaye

when i connect my headrest in the back of the seat, the ECU seems to get confused & won't allow any motor to move
i assume it is the sensor feeding bad data
anyone tackled this problem?

mark

Amskeptic

Haven't had that problem, but see if you can narrow it down with a little strategy. Remove seatback and see if you can unplug above sensor, then insert headrest. You may also have a wiring abrasion type of short or open circuit. And the usual Lexus Repair Manual admonishments apply: check all connectors and grounds and fuses and whatnot.
Colin

mkaye

it is the sensor that is bad (motor was always plugged in)
i did the diagnostic check as per the manual & the sensor output is always 12V
i move the the motor to both ends & the DVM never waivers measuring the output of the sensor (i could get the scope out to see if the pulses are there, but since the DVM never changes i am assuming i just have a steady 12V)
is it possible to repair the sensor or is it something i can replace?

mark

Amskeptic

They suggest using an analog meter, Seat ECU grounded at CHK terminal and count the pulses while moving the component to the end of its travel. At end, pulse is 1/2 second. During travel it is 1/4 second. Do you have CHK grounded?
ColinWhoHasNotDIagnosedThisCircuit . . . EVER

mkaye

i am just using the sensor & motor connectors (not at the ECU)

mark

mkaye

i have the sensor in my hand - a small circuit board with a transistor on the back side that must sense the shaft turning, and a couple caps & a small IC
it looks like the transistor switches 1 of the caps in & out to vary the oscillating freq, but mine isn't oscillating
i touched all the solder connections
so, unless i can get a circuit diagram or a replacement, i think my headrest stays where it is

mark