Merry Christmas one and all.

I noticed a few days back that the range on the key fobs to operate the locks was getting very short. Today the fobs (plural) wouldn't unlock the car, it would unlock by grabbing the door handle. So I replaced the battery on one fob then I was locked out entirely and had to use the emergency key.

Once entry was gained I started the car and switched it off. Exited the car and the touch sensor lock was again working but still no buttons on the fobs are working.

The main battery voltage is 12.22V so low but not too low. Couple of questions, well three actually, for people.

Is the c/l module run of the main or ancillary battery. The main is fairly new whilst the ancillary is original so now 8 years old and probably due a change.

UPDATE -
There are no obvious codes. The handle grab has stopped working and the car says the fob is no longer in vehicle even when it is. I can still get the car started by placing the fob against the steering column. The situation seems to be degrading by the minute.

Are there any OBD codes to look out for or specific modules to test if the scanner I have picks them up.

Are there any means to test if the fobs have lost their sync?

I’d say your system voltage is too low, nothing more.
Charge or replace the main battery. When the voltage drops, the system will begin to shut down circuits to conserve power, causing unusual behaviour.
It’s not the key fobs, it’s the car, -what are the chances BOTH fobs go AWOL or get dead batteries at the same moment? About a billion to one!

Also, you really need to think about DISABLING keyless entry before the car disappears off your driveway one night, it’s a big theft risk!

Search above for “disable keyless entry”

A sluggish tailgate is a sure sign of a weak battery in the L405 -how’s yours? “If it ain’t broke, don’t fix it” -where’s the fun in that?

Quote:

A sluggish tailgate is a sure sign of a weak battery in the L405 -how’s yours?

I did perform a hard reset by disconnecting the main battery for 10 minutes which didn't resolve the fob issue. So, I'll put the battery on charge tomorrow. The main battery is only 18 months old. I replaced the original battery because it wasn't holding a proper charge when the secondary aux battery was fine on charge.

If it is a simple voltage issue I'd expect things to work when the battery is charging at 14.7V with engine running. But the tailgate button still doesn't respond.

I doubt its a rf module problem as it was not a there one day and gone the next but a gradual fade away over the last 2 weeks. I'll recharge both batteries tomorrow and see when that gets me and report back.

The opening speed on the tailgate seems normal.

AFAIK the second battery is only for Stop/Start, (I don’t actually have one myself).
Sounds like there could be a parasitic drain, slowly dropping the voltage when parked, you can get a little BT module such as the Vgate to monitor the voltage on your phone, after the vehicle is shut down and gone into sleep mode.
Do you do mostly urban driving? With the fullfat, it’s easy to discharge the battery significantly in a short city run of say 1/2hr, which then takes a 5A CTEK a few hours to replace to full SOC, especially in Winter, when you have more stuff switched on, it could be 4 hours until full SOC is reached, (in cold temperatures the battery is slower to accept charge, which is why a smart charger will charge at a higher voltage if it detects low temperature, it can go over 15V.) If the charger is say at 14.7V, that doesn’t mean the battery has yet reached full SOC.

Our fullfat does four 16-mile urban overnight return journeys a week, but is always plugged into a CTEK MXS5 when at home, otherwise (even with a new battery), the SOC will eventually deplete over a few weeks to the point where things (tailgate for example) may function unexpectedly.

Interested to see what charging both batteries improves, I’m not sure if a wear auxiliary battery can drag down overall system voltage.
I think the hard reset involves touching the two (disconnected) battery cables together for a short time, I hope others can confirm this? Interesting the tailgate fob button is affected. “If it ain’t broke, don’t fix it” -where’s the fun in that?

Charging the main battery for 5 hours didn't make any difference.

I took to car around to a mechanic matey who has a Snap-On code reader to see if he could pick up anything my code reader hasn't but the answer was no to that. So, it'll be off to the garage to see if they can track down the problem which is pointing to the RF module as a prime suspect.

I bought the main battery from Halford's 2 years ago and it has a 5 year warranty so I dropped in there after a 40 mile run that had the battery showing 78% of capacity charge and a voltage of 12.17V. They put their battery tester on and it said good battery, just in need of a charge. Halford's will only exchange if the voltage is below 10V.

The car condition continues to deteriorate, now the auto lights also doesn't function. It's as though it is entering a slow but expanding electrical shut down.

Sorry to hijack this thread slightly, but where is the auxiliary battery?

I have a 2015 Autobiography. The main battery is below the the spare wheel, but i haven't seen an auxiliary battery. 2015 Range Rover Autobiography 4.4 SDV8

The secondary battery is behind the right hand card. Lift from the bottom first then pull away from the tailgate side. It is held on by 6 press studs.

If you don't see the aux battery then you will have a capacitor instead.. ... - .- -.




Y. O. L. O.
.

Thanks Stan. I will check tomorrow. 2015 Range Rover Autobiography 4.4 SDV8

I found it. Crikey, I was expecting a typical auxiliary battery, not one big enough to start a medium-sized family car!

I couldn't see the LR part number. Does anyone know it?

The meltdown continues.

Yesterday the auto lights stopped working and the lower on exit came up with a dash timeout message.

Today the stop/start switched itself off and it cannot be switched on.

It seems the car is on a relentless and progressive shutdown process.

So, when my main starter battery was on the way out, I didn't get any messages, but weird things started happening. The upper rear tailgate would open, but wouldn't close and just beeped at me. The other thing that started happening was my easy entry/exit wasn't working (which got really annoying with the seat all the way down and the steering wheel up).

Fitted a new starter battery and reset the BMS and all was well. 2015 Range Rover Autobiography 4.4 SDV8

I fitted a new Halfords main battery 2 years ago which is on a 5 year replacement guarantee. I took the car to Halfords and their tester says the battery is good, even though I do have my doubts. I did get them to agree that if a garage confirms that the battery is at fault then they would replace it.

The evolving shut down does, to me, point to a can bus issue or a battery issue.