D4 trailer brake issue.

[TonyB-Oz]

I got my D4 SDV6 MY11 new last year specifically because it had a great reputation for its towing ability.
I am pleased to say that it lives up to its reputation with flying colours but..... One small issue that maybe someone can assist me with.
I have installed a Tekonsha P3 electronic brake controller to assist with towing my 2.2T caravan as per sneigy's instructions on this forum and again this worked perfectly until just recently. I had the car serviced by the LR dealer where I purchased the car and since the service, when towing if I engage the cruise control the car throws up a fault light and goes into limp mode - I clear the fault with my FaultMate and all is good till I try the CC again, any one else had this problem? Never happened before the first service was done and I had towed many times without issue.

[Graeme]

Did you install a diode in the wire from the brake light to the P3?

[CaverD3]

If it happened after the service I would ask what they did. Did they do updates?

[TonyB-Oz]

I asked when I picked up the vehicle but there was no one around that could answer the question other than that if an update was due it would have been done.

Also as per Sneigy's instructions the additional diode was not required in the new model D4 otherwise I would have fitted whatever was in the instructions.
Again.... It worked perfectly towing for over 10,000 klms in the first year, only happened after the first service.

[Canaussie]

Hey tony,

I believe if you re read sniegy's post you will see on page 4 that diode is required on D4. As he said if install completed by him he would fit the diode.

Is it possible that maybe one of the wires has lost a bit of insulation somewhere and is rubbing, or a possible high resistance joint??

Anyways hopefully you get it sorted!;)

Cheers billy

[TonyB-Oz]

Thanks for your help Billy, I'll certainly checkout out the wiring again, but in response to sneigy's post I just copied this line out of it as follows.

On the new vehicles there is no 2nd fuse box in the rear nor the need for the Diode.

I took him on his word and it did work perfectly well until the last service, and since then every time I tow and try to use the CC it does the same thing.

Thanks for your help all the same, I will check out the wiring.

[Graeme]

I think the fault code needs to be checked.

[DiscoDavey]

On the new vehicles there is no 2nd fuse box in the rear nor the need for the Diode.

Hi Tony,
You needed to read to at least page 11 to see the bit about the diode. Perhaps sneigy should edit his post especially given how many people are using the thread as a reference. Here is what he said anyway. Hope it helps.

"I have had a misunderstanding with LRTech when the D4 was released & the info I have supplied is incorrect, I thought I was told a diode was not required, but have now been instructed to fit a diode to all ETB units fitted to any LR product. :(
So, a 3 amp diode from any electronic shop costing approx 30c will suffice.
Just tap into the red wire before it exits the l/h/r to the outside, just make sure the kathode end (the side with the stripe on it) faces the Electric Trailer Brake unit.
That will rectify the problem.
I strongly apologize for any problems that may have arisen from this."

[Graeme]

What fault code does Faultmate show?

[TonyB-Oz]

Graeme, as per my previous thread,

My 3.0l D4 brought up an engine system error last week followed by a sudden loss of power etc. I rang the dealer and they instructed me to lock the car for a few mins and then unlock and restart the car, this I did and the power returned thank god as I was in the middle of the Pilbara, WA - miles from anywhere towing the family caravan with the whole clan on board.
The error message on the dash however did not clear even after disconnecting the battery as told by the dealer. I have towed the van "as is" many times since I purchased the D4 with no problem at all. As I am so far from the dealer in Perth I decided to live with the message till the next service which is a while off as it's just had one. Got a faultmate from Cyprus within a week and cleared the codes successfully.
Like to know what the codes mean if anyone can help.
P3201-P062B
Other than this little problem that could have been my doing, this is an absolutely brilliant vehicle, and towes my 2.2t van beautifully.

You did make some suggestions about the codes at the time Graeme, but as it only occurs when towing and using the cruise control I have looked no further into the actual faults.

Thanks again. I will be getting a diode as soon as I can find one online or the next time I get to Perth.

[Graeme]

Hmm, I was thinking about an ecm fault because the diode is only needed for those brake controllers that turn on the brake lights when the emergency brake function is used or as a preventative if a controller fails and appplies power to the trigger line, as either would produce similar results to a faulty brake light switch. Because of your ecm's previous strange behaviour I'm even more favouring an ecm fault although it is possible that LR have introduced logic and a fault code for illogical brake light switch operation.

Fitting a diode would be prudent although I haven't fitted one to mine yet. As mine has just had the latest ecm s/w applied, I will fit my P3 and try CC tomorrow or perhaps later today although without the van, the P3 wont try to operate so most likely of no help.

Edit: Tried the P3 + CC but without the van, even using the brake lever without any abnormal behaviour. It needs the van attached to get a comparative result though.