I bought a 1999 Land Rover Discovery II from old British car mechanic but he wasn't a very good mechanic and he left it in his front yard for years until it would no longer run or start.

Here is what I have done so far:

Cleaned the truck inside and out because the sunroof was leaking and it was very moldy inside, none of the switches for the windows etc work because of the water.
I replaced the fuel pump because I thought it was the problem, so that is new and I can hear it working.
I have run a wire from the starter solenoid to the battery to crank it over because the key will not start the truck.
When I turn the ignition on the M & S lights flash on the dash and so does the "gear indicator?"
One of my scan tools says the truck thinks it is in 4th gear all the time, the other says it cannot communicate with the module.
I have removed the XYZ module and taken it apart, the microswitches look in good shape but it is expensive and I don't want to replace it if I have bigger problems.

If I turn the ignition on and use my wire ran to the starter solenoid the engine fires up and sounds good but dies a second later, the key needs turned off and back on again before it will start again for a second.
When holding down the gas pedal and starting it the engine revs up and sounds great but also dies a second later.

The immobilizer light is not illuminated but it seems like I have a computer system that is killing the engine when it starts, I tried the default immobilizer code just for fun but I am not sure it would even work as none of the power door locks function either.

Does anyone have any guesses on where I should look to get the engine to stay running? This truck is actually pretty nice to work on so far and I would to save it if I can but I when dealing with the computer I am not sure where to begin. I do have very expensive scan tools and can run tests if anyone has an idea.

 

Sounds just like a bad MAF sensor. Unplug it and see if it runs any longer.

 

I'm assuming you're getting code P0734, which is actually a sign that the MAF is bad.

I would also remove and clean the idle air control valve, and replace the spark plugs and wires. They probably work, but you want to make it as easy for your engine as you can to maintain a spark. The inability to start the car using the key is probably a bad relay. You'll find it in the engine compartment fuse box. Check all your fuses and relays while you're at it.

I would also check your computers under the glovebox for mold or signs of moisture intrusion.

Regarding the XYZ sensor, it may just be misaligned. It has a certain degree of rotation. Make sure that the gear indicator on the dash shows the actual gear for all gears, and rotate the switch as needed if one doesn't show up. Since you have it out, you can also check for continuity at the plug under each configuration. There are charts online for what that should look like.

 

I disconnected the MAF sensor and it is exactly the same it runs for a second and then stops.

 

Are you modulating the throttle when you start it? If you're having trouble maintaining idle, you should be able to keep it running with your foot. If you can't, it's likely something more significant.

 

I only got code P0734 when I started the truck with the MAF disconnected. The only engine code I am getting is DTC 94 "Anti-Theft Alarm Serial Link"

I did check all the fuses and only one was bad, the one for the radiator fan which I have replaced.

I moved the XYZ Sensor when I had it out with a screwdriver and connected to the truck and it never showed any gear except fourth on my scan tool, it is either bad or not communicating at all.

 

The engine runs great it is obvious that the computer is shutting it down. It is not like it is barely running or stuttering.

I did find this and it sounds similar to what is going on with my truck but I am afraid I have too many parts of the security system that are not working.

 

Yeah, it sounds like it, and unless you want to replace the rest of the systems first, you should probably just get it reprogrammed. You can't swap a used BCU in without getting it synced to the ECU, which is probably just as expensive.

 

If I buy a Nanocom will that be able to do this or do I need to take it to the dealer?

 

Once the immobilizer is on, you can't communicate with the BCU anymore. Once it's disabled, you can use the Nanocom to permanently turn it off, but you're probably best off bringing it to Land Rover for this one. It's always more fun working on fixing a car that you know will run.

Edit: your other option is to find a junkyard Disco and pull both the ECU and BCU. But obviously no guarantees there.