Thread: Transmission fault/HDC fault

Originally Posted by Timj

Hi All,

I have these errors coming up and have had the fuel gauge sender in the tank replaced and the fuel pump in the tank replaced due to hard errors on both of those. But the errors are still coming up. If the brake sender or brake lights are an issue will it happen even when not touching the brakes? Mine seems to always happen when putting the accelerator foot down, usually on slight rises and has even happened when the cruise control was on and accelerated for a rise. I have a Tekonsha P3 brake controller that usually stays in the car and connected but it has happened with and without a trailer, today it happened with the boat trailer which has override brakes so the controller is not being used.

Thanks,

TimJ.

Tekonsha P3 brake controller on my D3 and a another car had the brake lights staying on Tekonsha agent has offered to replace both my units! Un plug it and I bet your problem goes away. It is intermitent so you might hang onto it like I have or seek a refund. Just do not leave it pluged in!

Originally Posted by adzee

So if you changed the bulb in the D3 what ones(LED version/part #) did you get? I thought if you changed to LED it would disrupt the computer checks or something and u couldn't do it? I am keen to swap them cause I have gone through 3 globes in 7 months...

I swear by having a spare brake light switch in the glove box!

see my post and the links other people kindly provided. My LED globe and other people who have them give me no problems. Love them and love that the issues which occured every 50k or so when a globe went such as DSC, Gear box, Suspension and just about every thing else that good be reported are a thing of the past for me now and only an issue for those of you who haven't replaced your globes with LED yet to chat about
Hint - Get the white LED globes do not bother with the red for LED stop or tail lights.

Originally Posted by weakestlink

Tekonsha P3 brake controller on my D3 and a another car had the brake lights staying on Tekonsha agent has offered to replace both my units! Un plug it and I bet your problem goes away. It is intermitent so you might hang onto it like I have or seek a refund. Just do not leave it pluged in!

Still having the problems having changed all four bulbs for genuine ones and disconnecting the brake controller. There are a couple of errors being recorded that suggest there might be a problem with fuel pressure in the injectors or fuel rail. Being investigated at the moment, though why they would cause these three errors is unclear, they seem to be the catch all errors, if you can't be certain then give em every error you can. Would be funny except it isn't.

Cheers,

TimJ.

I get this fault reported reasonably often, perhaps once a month or so and it does seem to be pretty random. I haven't bothered replacing lights or switches to try and clear it as reading on the subject seems to show it is general unexplained condition somewhere and the error codes don't pinpoint it. LR also seem to ignore the codes during services and I haven't pushed the point with them to try and fix it. I suspect a lot of sensors etc would be replaced and it will still occur so until I know exactly what causes it I won't replace stuff.

Whilst I can clear the fault by restarting the car and the warning lights goes off after several starts and stops during the day this is a worry.
What I fear most is that a "real" fault with the transmission will occur one day and it will be dismissed by the other half as the same thing occurring and some serious damage will be done.

A bit like the boy who cried wolf.

I can understand you not wanting to start replacing parts willy nilly - chasing false error messages so to say.

For me, it was every winter when it got cold, I would start to get transmission, cruise control and HDC error messages. When the weather finally warmed up by June, the messages would cease for a couple of months or so until it again cooled down a bit.

In frustration, I finally changed out the brake light switch myself because it was easy and cheap to do. Now this winter and to date, no false messages any longer. The link below is to my gallery where I have some pictures and install instructions for the brake light switch. Regardless of where the steering wheel is, the switch will be near the brake pedal.

I might add that all my bulbs were genuine LR and that all lights were working fine so changing the switch really seemed like an act of faith or more correctly, nothing ventured, nothing gained. This time, I figure I won.

DISCO3.CO.UK Photo Gallery - Brake Light Switch Replacement

Actually the switch is the one component I was thinking of changing. Might change that from thinking to actually doing in the near future.

Regarding the brake light switch, I have a theory that while the switch appears to be working just fine, it is responsible for creating spurious signals that lead to the false error messages.

Within the switch, the set of contacts that is normally open operates the brake lights; the other set of contacts that is normally closed sends signals to the ABS module.

I theorize that dust from the deteriorating brake light set of contacts fouls the ABS contacts and leads to intermittent operation of the ABS contacts during normal driving particularily when one is not using the brakes. Since the ABS circuit communicates with the Hill Decent circuitry and that affects the transmission and engine controls, then anything is possible. For the most part, we are fortunate that all we get are false error messages and threatened system shut downs.

As to why other vehicles do not seem to suffer this malady, well no other vehicle, (except maybe some Jeeps just recently), has a Hill Decent system.

Originally Posted by bbyer

As to why other vehicles do not seem to suffer this malady

LR seem to like to cross-check their mechanical switches. The D2 ABS modulator uses resistors across the contacts of 2 series switches so that the correct or otherwise operation of the switches can be detected. The D3/4 brake light switches are another example of cross-checking a mechanical switch. However its likely that when the contacts for operating the brake lights get corroded and worn with use due to switching the power to the globes, they don't make and break cleanly or with the same precision as the other set of contacts which stay in good condition because they have basically no load, as the ecu draws only a very low current. Hence the ecu gets mixed indicators as to whether the brake pedal has been pressed or not. If LR wasn't trying to be so perfect and only used the brake light power as the indicator then there would never be a problem, excepting that when the contacts corrode sufficiently then there would be no indication to the ecu that the pedal was pressed. I prefer the extra checking but there could be a better indication that the brake light switch must be faulty.