Geetings! I'm new to this forum but own a Discovery -96 V8i since 10 years. Now we got a strange problem with it.
Symptom: Locking and engaging alarm with FOB(2buttons) then comes out the day after and the doors are unlocked. It is not possible to use FOB - nothing happens when pushing the buttons. Alarm sets of when opening door with key. I then disconnected the battery to get rid of the alarm noise.
Checking battery and its a bit low so I charge it over night. Put back the battery the next day and the FOB worked, it was possible to lock/unlock and turn the engine on. I thougt the problem was solved with a fresh loaded battery(it's a bit cold here now which takes a toll on the battery).
The next morning I come out and discover that the doors where unlocked again and now the FOB won't work no matter what we do. I have tried to push the FOB button 4 times to reconnect but nothing happens (and changed FOB battery).
And what is more: The central locking doesnt work, I must unlock all doors manually. The Alarm LED indicator doesn't flash and I can naturally not start the engine due to the immobilizer.
Now I have searched the net all day for an answer and cannot find a sollution. I saw some tips about the "spider" unit but I figure it must be something else. Anyone got a clue?

 

Unhooking the battery to "stop" the alarm is the wrong thing to do, the alarm has a battery and it remembers the last thing it was doing before it lost main power (car battery) and when you hook the battery back up it will stay in that mode that it last remembered.
Basically you screwed yourself by unhooking the battery.
When the alarm is set off it will only sound for 3-5min and then stop, reset itself and you can try again.
Now you need to either tow it to the dealer or dig into it and hope for the best.
Pushing the fob buttons any number of times you want will not make the fob and truck talk to each other.
In the DI tech section is a write up on what to try, including entering the EKA code.

 

Thanks for your quick reply Spike555!
I tried the EKA code 1515 (I don't have the original code). But if I understand correctly there should be a sound indicating that the system is ready to accept the code, and in this case there is no sound.

I checked all fuses that i could find and they where all good.
When trying to ignite the engine, there is a rattling sound that seems to come from the alarm unit(amr 4886). If else it comes from something behind where the AMR 4886 is located.

I might add that we ran the car through a car wash shortly before all this started. The door to the driver side was not shut properly so there was some water on the inside. And it has been around -5 degrees celsius outside. Could that has caused the problem?

I surely hope this is possible to fix without towing it to a dealer.
Could a bypass of the spider be a sollution?

 

Bypass would be good.

 

I highly doubt the cold and car wash had anything to do with it.
I will give you a tip though, never wash you car, any car, when its going to be below freezing, that is a guaranteed way to have tons and tons of problems, like frozen door locks, frozen windows, hood, trunk...never do that unless it is sunny, and you do it first thing in the morning and let it sit in the sun all day to dry.
Even though its freezing the sun will heat the car enough to evaporate the water and keep it from freezing.

 

yes I know it was a bad idea to wash it but it was full of road salt so it was either take a chance or get the car even more corroded.
Anyways, I took out the alarm unit to have a look at it and this is how it looks inside - the oxide on the components is a prime suspect. We will try to clean it in hope that it still works. Else we will have to find a replacement.

 

You've got a few problems. The oxide yo see on the board is acting as a conductor, and you need to remove it. Some type of alcohol, or an actual solder flux remover with an acid brush would be best.
Unfortunately, a lot of what you need to remove is going to be under parts where you can't get at it. You can try using the alcohol in an ultrasonic bath is you have one.

Any type of solvent will melt some of the parts.

Even if you get everything off, that may not restore it to operation.

If you need to replace it, you'll either have to have the ECU reprogrammed to recognize the code of the new unit, or get an ECU and TPU that are already matched.

 

By the way, the 1997-1999.5 Discoverys don't have the alarm spider. All of the functions of the spider are handled by the alarm itself.

Although it's possible to bypass the starter disable on the alarm unit, it still needs to send the enable code to the ECU for the truck to run. Unlike the earlier trucks that could disable the fuel pump and ignition as well as the starter, those are the only methods the system has to disable the engine on 1997-1999.5 trucks. It might also apply to 1996.

You can bypass the starter disable by connecting the black wire with the orange stripe on the smaller connector (pin 11) directly to ground. If the alarm hasn't sent a disable signal to the ECU, you may be able to start & run it.