Land Rover Repair: unable to access ECU vehicle systems, land rover discovery, obd interface

Question
Dear Sir
I have Land Rover Discovery 1995 and i try to read the diagnostic but it's unable to access vehicle systems the dealer say changing engine harness !! and some say chaining the ECU any Idea please
Thanks
Hany

Answer
Hi Hany,


it's possible the harness has a fault.  In cases like this, it could be one of three things:

1. OBD interface (or engine harness?) is faulted;
2. ECU is faulted;
3. OBD reader is faulted;

I imagine the LR dealership having trouble to connect would have a fully functioning reader, so #3 is not applicable.  

It's rare to see a failed ECU but it can happen.  A new ECU is expensive and then there's the reprogramming to be done.  Could be up to $3000 at the dealer (at least my dealer wanted to charge me this).

IF your LR dealer suggested a new engine harness, it's quite possible that this is the case.  Perhaps corrosion or a short is causing the problem.  I think this is the least expensive of the two options.  Just make sure that the dealership is willing to accept responsibility IF the harness does not resolve the problem.  It would be a shame to have this replaced and find out it was the ECU all along.  

Another possibility is that the OBD connector is faulty.  Maybe a new interface is all that is needed.  An inexpensive option that could be considered.

Best of luck,

JohnMc