Merriam Webster:
Koan -- a paradox to be meditated upon that is used to train Zen Buddhist monks to abandon ultimate dependence on reason and to force them into gaining sudden intuitive enlightenment
Sounds like a very fair description when it comes to interpreting the wisdom of some parts of The Great Book a.k.a. the Factory Service Manual (FSM)!!!
A similar problem followed my discovery that the tail-light on my 2006 LC100 did not appreciate being backed into a fencepost, the “bulb” (being an LED array on that model) then stopped working! The 2006 LX470 is electrically similar below the skin ….
The FSM in its various versions will have had a large cast of different authors – some writing in Japanese and translated later by others, others writing directly in English as a Second Language. My own life experiences included many work relationships with Japanese business and technical persons over many years. In the case of Japanese Toyota/Lexus persons, the professional competency and technical proficiency will be very high. However, sometimes English language proficiency may be variable. It also can happen that the wording chosen and written in English is too literal, more so than a native English-speaking reader might expect.
These are my suggested "translations" of two cases:
Case 1: “Only one light [always] come on” -- “always” means
always – and means power
always is running in the circuit, for example if Ignition Switch is ON,
regardless of whether the brake pedal is pushed. This requires a fault condition. The FSM suggests harness fault (also includes connectors), cannot be the stop light switch, cannot be the relevant ECU because either of these would affect
both side brake lights
and the high stop light – see circuit diagram at the link below. (By the way, the stop light circuit also links to both the ABS ECU and the AHC ECU. If either of these are receiving a “Brakes are ON” signal from these kinds of faults, then ABS and AHC problem symptoms and warning lights also may appear).
Case 2: “Only one light does not come on” – means what it says – whatever the driver does, including pushing the brake pedal, only one light
does not come on.
You will know whether you have Case 1 or Case 2? It seems more likely to be Case 2.
If Case 2, the problem is either
- a harness issue, broken wire somewhere, or simply a loose or damaged connector (sometimes happens when the jack and tool roll are taken out of the LH rear fender, or when wiring is rearranged or disturbed when a rear bar is fitted, or when other changes are made,
OR,
- for a model later than May 2005 the “globe” has failed (which for this model actually is the LED array, not a single globe) – and expensive replacement of Lexus 81561-60700 is required unless a spare can be found from a vehicle being parted out.
Suggested first steps:
- Remove light assembly
- ,
- Test brake light by applying battery voltage,
- Request assistant to apply footbrake, check voltage being received from vehicle harness at the connector which is revealed when the light assembly is removed.
References:
Circuit for LC100 after May 2005 (LX470 is similar)
https://lc100e.github.io/pdf/ewd/em0020e/htmlweb/ewd/contents/system/main/OVER097.html
Routing:
https://lc100e.github.io/pdf/ewd/em0020e/htmlweb/ewd/contents/routing/main/WR012.html
