alarm system problems
 

Please help. I cant's start the engine due to alarm system problems. I have a 96 discovery .
I went to advance autoparts local store and used their scanner to check my discovery 96,the alarm system came on and i was able to start the engine only using the generic code 1-4-1-5 in the driver's door lock. That solved the problem for a while but now the generic code doesn't work anymore and the car is useless sitting in the parking lot. Any help is appreciated.

What does the red alarm light on the dash do?

alarm problem
 

Thanks for the reply. The red light is always off, it doesn't blink anymore like use to be before. The light comes on when i try to start turning the key.

When you say it won't start, what exactly does it mean? Won't turn over or won't run?

if the light does this, you are in fact in immobilzation.




Does operating the driver door key unlock the ther doors or just the driver door?

If the driver door key is no longer signalling the central lock system, because of broken switch on the door lock, your signal may not be getting to the alarm unit, which has to tell the ECU it is OK to run the truck. You can try using the key fob if you have a working one.

alarm problem
 

it does not run

I was under the impression that the earlier "spider" unit disabled the starter when it was immobilized.

I think in 96-on it did both. Some RAVE notes from 96 circuits guide for theft alarm (NAS):


7. Engine Immobilisation function.

and

Central Locking is controlled by the Theft Alarm Unit
(Z163) and may be locked by using the driver’s door
key, sill button(s) or handset. The vehicle may be

unlocked by using the handset or EKA code.

(if truck is not being unlocked all around by the driver door switch, and the EKA is no longer working, that would point to a problem with the tiny switch on the door lock itself).

and

Engine crank inhibit against unauthorised engine crank.

Electronic engine immobilisation against unauthorised engine start.

and

ENGINE IMMOBILISATION FUNCTION

The engine will be immobilised whenever the theft alarm is armed.

The vehicle may only be mobilised by using the

handset or the driver’s door key.
The electronic engine immobilisation is controlled
jointly by the engine management system’s
Electronic Control Module (ECM) (Z132) and the
Theft Alarm Unit (Z163).
When the Theft Alarm Unit (Z163) immobilises the
vehicle, it sends a signal to the ECM. The ECM then
immobilises the engine management system until a
mobilise signal is received from the Theft Alarm Unit

(Z163).

The act of locking the truck is supposed to arm the alarm which then immobilizes the truck, even though alarm is not triggered. Operating the key fob or the driver door "re-mobilizes" the truck by exchange of coded data with the ECU, which in effect tells the ECU it is OK to obey driver commands because alarm system considers him to be authorized.

So if the EKA is no longer working, then you can physically unlock the truck, but the alarm box has not been instructed to pass on the information to the ECU.

From the Lucas 10-AS alarm module manual -

GEMS code

:This is the code transmitted by the 10AS alarm unit when GEMS is selected as the engine immobiliser option. It can have any value between 0 and 65535.

That would indicate that a digital code is exchanged between the alarm and the GEMS ECU. The ECU is waiting for the code, so if the wires are cut or shorted, the code won't be sent. The alarm system sends that code when the driver door key input or key fob input is toggled.

The door switch can be checked under the driver footwell at connector C2101, it is the blue with green wire on pin 3 of that 13 pin connector. The switch is normally open, and touches to a ground lead when turned. The ground lead could be broken, then the driver door lock would also not work. The switch could be bad, or mechanical issues, or the wires in the frame to door bundle could be broken and make/break with a mind of their own.

I would suppose you could key in the ground sequence manually, worked in the first Star Trek movie.....

Or it could be the wire between the alarm unit and the ECU.

If I had access to the program tools I would disable the immobilzation function in the vehicle. That is what insurance is for. I guess the cost trade off was add immobilzation and leave off oil gauge. It is such a PITA when this breaks and you are more than a stone's throw to the dealership.

And if stored configuration program in alarm module or GEMS ECU is corrupt (just data, never politicians) you have more problems.