Transmission fault, HDC, lowered suspension height -- resolved

[Houm_WA]

I don't think you are out of the woods yet, unfortunately. The MAF can account for the REP message, yes. To me, the other issues could be the Steering Angle Sensor, or a Parking Brake Switch, or a bad tail/Brake light. I would look at those things if it happens again.

 

[Koladeabel]

Every other thing is perfect. The car is running fine. Many thanks to you.

 

[Houm_WA]

Okay....glad to hear it. I have a feeling you'll be back, though. The things I've suggested checking are easy and cheap. If you're good, you have spares.

 

[Koladeabel]

Okay....glad to hear it. I have a feeling you'll be back, though. The things I've suggested checking are easy and cheap. If you're good, you have spares.

All noted. Thanks for your concern.

 

[JayMN]

This happened on my 06 LR3. Transmission Fault, HDC, Suspension Lowered. Codes go away when I restart the car. After changing the break light switch, codes continue to come back for 2-3 weeks, but never occurred again after that. Don't know why the break light switch would have anything to do with Transmission and Suspension, but changing the break light switch definitely fixed it.

 

[bbyer]

This is a link to the brake light circuit wiring diagram that perhaps gives one an indication of why a faulty brake light switch can effectively disable the 3.

http://www.disco3.co.uk/gallery/displayimage.php?album=5082&pos=9


Below is a brief summary of some of what can be affected.

Stop Light Lamp Circuit wiring diagram


The pdf shows the brake light circuit for the NAS LR3.

Note that power for the brake light bulbs can come either thru the brake light switch power feed /contacts plus also from the Hill Decent Control, (HDC), system relay located within the Central Junction Box, (CJB) - yes two separate sources of power for the brake light bulbs.

This would tend to explain how a brake light circuit concern shows up as a hill decent fault message; also why lesser vehicles without hill decent braking mechanisms, (HDC), never display this sort problem when a brake light bulb or switch acts up. You never have a problem related to a system that does not exist.

Additional evidence of the relationship of the HDC and the tail light circuit is demonstrated by when the HDC actually acts to slow the 3 down, the brake lights automatically illuminate even if the slowing action was merely retarding the engine speed or shifting to a lower gear, (in other words, no foot on the brake pedal).

There is also a tie in to the Cruise Control circuitry and hence a failing brake light switch can affect cruise operation or just create false Cruise Control messages. Additionally, while there are no messages generated, operation of the radiator electro viscous fan can also be negatively affected by the fouled set of secondary contacts within the brake light switch. This is all because the NC contacts within the brake switch send misleading messages to the ECU.

While the ground wire design is similar to other vehicles, note the grounds for the brake light filament and the reverse light filament are common on each side. That means that if one has a non functioning brake light on one side, the reverse light may not also work or that some problem with the reverse lights could back feed into the brake lights. This situation while unusual, can result when grounds are corroded probably due to swimming in rivers and creeks or just routine driving in a marine environment.



This link contains further info regarding the brake light switch.

http://www.disco3.co.uk/gallery/thumbnails.php?album=5082

 

[bbyer]

Below is a link to a 17 page LR pdf related to the braking system and subsystems.

I see it only has a thousand views in contrast to the over 5,000 views related to changing out the brake light switch, however the 17 page pdf does a good job of twisting your mind.

We have come along way from the single trunk lid located brake light on my Grandfathers 1947 Dodge Special Deluxe 4 door. I might also note the chrome push button for the electric starter motor was standard - so that has made the circle.

http://www.disco3.co.uk/gallery/displayimage.php?album=5082&pos=1