Failed lamp sensor fix

Failed
Lamp Sensor Fix

 

Symptoms:

  • The
    (4) rear brake lights do not work, medications except for the LED brake light on the
    hatch.
  • The
    (4) rear taillights (same bulbs, viagra different filaments) work OK
  • Fuses
    are OK and the filaments for the brake lights in the bulbs are OK

Diagnosis:

  • Most
    probably, sildenafil the Toyota Lamp Failure Sensor (LFS) has malfunctioned.
  • The
    LFS (P/N 89373-14080) is in the brake lamp circuit for the (4) rear lamps.
    It is NOT in the circuit for the LED lamp which explains why the LED lamp
    continues to work. Its purpose is to sense when a lamp filament has burned
    out and notify the driver by a warning lamp on the instrument panel.
  • Unfortunately,
    there is no sensor to detect when the LFS itself malfunctions, and the
    driver is simply left without brake lamps (except for the LED)
  • Often
    (at least 4 known cases) the LFS has malfunctioned simply due to a cold
    solder joint, or a cracked trace on its printed circuit board. These can
    be easily repaired and will save the owner a bundle. (Most Toyota dealers
    charge over $225 for the LFS part alone.)
  • The
    LFS is in a small light blue plastic case (about 2” x 2” x 1”) and
    is located in the left rear quarter panel of the Supra, in the well behind
    the wheel. It’s easily accessible by removing two plastic covers in the
    rear hatch.

 

Tools
Required:

  • #1
    Phillips head screwdriver
  • Low
    wattage (<25 watts) soldering iron

Time
Required to Fix:

  • Only
    about 20-30 minutes

Procedure:

  • Get
    your soldering iron plugged in so it’ll be ready – the rest of this
    will only take about 10 minutes…
  • Open
    the rear hatch and peel back the carpeting on the left rear side (see
    photos)

 

 

 

  • Pry
    out the black plastic plugs covering the fasteners for the left side
    plastic panel, and the small triangular panel covering the left rear shock
    tower.
  • Remove
    the 5-6 phillips head screws for the side panel, and the shock tower
    panel.
  • Remove
    the (2) Toyota black plastic rivets – one is on the shock tower panel,
    and the other is holding the left side panel to the rear panel (covering
    the taillamp). Look closely for it, it’s there, but it’s buried!
  • Pull
    the shock tower panel off, and the left panel out – careful with the
    left panel – be sure to disconnect the interior lamp from its harness,
    and if you didn’t find that 2nd plastic rivet the panel is
    not coming out!

  • Locate
    the light blue plastic tab protrudng through the sheetmetal. It will
    probably have the hatch release cable and another harness running right on
    top of it. This is the LFS.

  • Reach
    into the well opening and hold the LFS with your left hand, and push on
    the blue tab with your right – it should pop right out.
  • Extract
    the LFS from the well, and remove the plastic harness connector.

  • Turn
    it over and see how the back fits on – remove the back to expose the
    printed circuit board.

  • If
    you look carefully at all the traces, you may be able to see a crack or a
    cold joint. Several list members who have had this problem reported
    finding the fault this way. With your soldering iron carefully try to
    bridge the crack with the existing solder on the board (there’s plenty),
    or touch up the cold joint. Try not to add new solder as it may bridge
    traces where it’s not supposed to!
  • Either
    my eyes were too old, or my LFS simply had a cold joint which I couldn’t
    detect. After staring at this board under a magnifying glass for 10
    minutes, I took the easy way out and “touched up” every solder joint.
  • Don’t
    reassemble just yet, but reconnect the LFS to its harness and see if you
    have brake lights now. If you do – congratulations! You’ve saved
    yourself at least $300-400 in dealer service charges.
  • If
    you don’t have brake lights yet, and you didn’t resolder every joint
    on the board (as I did) – try this approach now, maybe you have more
    than one fault. Try not to add any new solder!! On my LFS I noted there
    was plenty of solder and I had to be careful that the excess didn’t
    bridge adjacent traces.
  • Assuming
    you’ve had success – reassemble everything! If no success, reach deep
    into your pocket for that $237 for the Toyota dealer. (If it’s any
    consolation, Jeff Watson at Jay Marks will sell it to you for $150)

 

Any feedback
is welcome!