ecu to engine harness

[juzzyvk]

hi everyone, i have been having some trouble with the engine light coming on in my vn and when i try to get the codes out the only thing that happens is the fan comes on, so today i finaly had time to take it to the mechanic to have a look at. he hooked up the computer to check for codes and it and all he got was cant communicate with ecu. now my car has a vr stateman interior and electrics in it from previous owner and i got the mechanic to check the plug under the steering column and he got the same problem, his answer was for me to take it to a auto elec to get it sorted out. the thing i want to know is if i replace the engine harness back to the ecu and keep the vn ecu will that possibly fix my problem and allow me to get codes, i have a friend with a vn padock bomb so i can get the looms for free just want to know if it is worth doing or if i should just take it to the auto elec thanks for any advice really dont know to do with the car.
juzzy.