Engine and Transmission Tech

Hey Kurt,
Are we talking NAS vehicles.
I don't have anything like that on my diagrams.
And I just tried it on my 97 shop truck and it won't fire.

what is your "shop truck "?

Im using Electrical Troubleshooting Manual Part No LRL0028

1997 disco
Ended up with a fault code P1621 and all the remotes had to resync.

I'm really interested in this. If it works then I can use the system from the 1996 I have on the 4.0.

Tim

it works been done for many years go look up the info in the manuals listed ^^^^^^^
I not going to list a how to on the web but the info is in the manuals :-)
or look a cat by the name of AFIROVER on discoweb he is the wiss at this stuff
..

I think that we have our wires crossed, as they say Kurt.
You and AFIROVER are referring to the starter lockout provided by the anti theft system "spider". And it can indeed be bypassed with a simple ground wire in the disco only. Land rover also sells a bypass plug for that unit that does exactly the same thing. That gets the engine to crank but it won't turn the ecu on.
The Lucas Sagem GEMS ecu must receive a security code from the 10-AS anti theft module in a Disco or the BECM in a p38. This code is in numerical form and can be any # from 0 to 65535. Once the ecu confirms the code it turns on the check engine light to indicate that it has be enabled. You can check for it on pin 26 with an oscilloscope. It's a square wave output.
Here is a direct quote from the manual.

"Security learn mode: When the ignition is turned on, the BECM, providing it is in receipt of a valid mobilization code and is therefore not in an alarmed or immobilised state, sends a coded signal to the GEMS which the Gems then compares against a mobilization code it has stored in it. If the two codes compare OK, the Gems will allow the engine to start. This forms the basis of the immobiliser. If the GEMS ECU, the BECM, or the lockset & key fob is replaced or other data in the BECM is changed, it may be required for the GEMS to re-learn a new mobilization code. This is done by using this function to put the GEMS into Security learn mode whereby the next coded signal it receives is not compared but is instead stored as the master copy. When security learn mode has been entered the ignition must be turned off and turned back on to trigger the BECM into sending the code. The GEMS will check the incoming code and should accept it; however, if there is an error no matter how slight in the codes makeup, the GEMS can reject it, in which case there will be no valid code stored. This situation can be checked by looking at the security learn status in Inputs - Engine and Other which denotes whether the system has a valid code stored or not".

Other than having the anti theft lockout removed from the ecu by RPI or some one similar. You can utilize the 10-AS module from a Disco and have it and the GEMS synced together. Or use a product from an Australian company called Mobi-lize. It's quite clever but you still need to visit some one like me with a "Test book" "Autologic" or "Blackbox" etc. to allow a security relearn.

I'm not trying to be difficult. I just don't want someone to go to the trouble of installing a GEMS system only to find out that it won't run in stand alone mode.

Cheers
Fred

Fred

I don't disagree with what is written but in practice I have found it not to be all that accurate .
now that might be that I have a Test book and a black-box solutions here that makes me both dumb and not to intimidated by this issue
if it was true you would not be able to swap out ecu from disco to disco (p38's are another matter) with out having to do anything my last 3 off road rigs have had the alarm ecu removed and one had dual ecu's( one has been reworked and one is stock ) with a spare back at the trailer that we will swap out on the trail( if needed ) with out any fancy gear :-)
K