Discovery 2 td5 can't communicate

Just to make it clear to you, unfortunately this is not decribed in any D2 or LR document but the principle is the same like in the attachment just take the BCU as the IKE/Kombi and the wire colours being pink(K) in this case so the connection between BCU and that header being interrupted the K line doesnt work as D-bus hence no comms with diagnostics, neglect the red star it was for other "customer" who had a BCU failure in your case it's what's below that star

Yes I get you nothing from bcu to pin 18
Q

If you are 100% that you work on the correct BCU connector check between BCU and all the other pink wires just to make sure and if no continuity better run a new wire cos chasing where its interrupted can be a nightmare

also if you route a new wire cut the old one cos if it's chafed somewhere it can get a short to earth in the future. Good luck and come back with a result

Hi thanks for all your help I will double check all pink wires header tomorrow and run a new wire and report back thanks once again

Hi sierrafery I have have double checked all pink wires and still won't communicate I have also put a new bcu on and still not getting any were
So far I have changed
Both fuse boxes
Ecm ( tried with new and old i took new of a running td5 )
Bcu again off a running vehicle
Replaced the wire and now have continuity but still not working

HI. So you have continuity between the OBD port and BCU and the tester doesnt comunicate with the BCU ?
1. Did you check resistance against earth on that path?
2. Are you sure that the scanner's pin 7 is reaching the K line in the diagnostic socket?
3. After you replaced the BCU did you let ignition on 2 for 5 minutes ?

Hi no I never had on 2 for 5 mins until I plugged the diagnostics in I have the key that is coded to bcu

Ok, it's good that you have the key but regardless of that after the BCU or IDM are replaced the ignition must be left on 2 for 5 minutes as the two units to regain digital data comms also i hope you disconnected the battery before the swap.

can you unlock with the fob with the replacement BCU ?

better tell me how this thing started and what diagnostic tool you have... i need all the information to be able to help cos any small detail can be relevant so answer to all my questions

Hi yes battery was disconnected I have hawkeye total diagnostic
And I drove home one evening and couldn't start in the morning no fuel pump running with ignition on

When trying to connect to bcu milage goes to 0 all other lights off and back on then just says serial error

milages flashes all the time with new bcu

A friend of mine come round with a unlocked ecu and it started straight up so fairly sure original problem was ecu

Now, answer to all the unanswered questions please otherwise i can't help. Again:
1. Do you have continuity between the OBD socket pin 7 and BCU ?
2. Can you unlock with the fob with the replacement BCU or with the old one?
If the fob worked with the old BCU put that back, let ignition on 2 for 5 minutes then unlock with fob and connect hawkeye then

Yes I have continuity between bcu amd obd no unlock doesn't work with new bcu and fob but I know it was working on vehicle I removed from and it fob never worked with old bcu I had to use door lock

Mattc90 said:

Yes I have continuity between bcu amd obd no unlock doesn't work with new bcu and fob but I know it was working on vehicle I removed from and it fob never worked with old bcu I had to use door lock

Click to expand...

So you can forget about the replacement BCU then cos it remains immobilised, put back the old one as i said and try then or did you already try with the old BCU after the circuit was repaired ?

Mattc90 said:

A friend of mine come round with a unlocked ecu and it started straight up so fairly sure original problem was ecu

Click to expand...

maybe but that doesnt change the fact that there was an interruption between the BCU and OBD so there might be other issues too

Hi I tried before replacement was installed the red immobiliser light turns off with both installed not sure if this makes a difference or not

the engine cranks with both BCU ?

I replaced k wire and tried to connect before bcu was replaced
I then installed new bcu didnt known about the ignition on for five minutes but the battery was disconnected when was replaced i have just been out and left the ignition on for 5 minutes and tried again i also made sure all obd wires were fully pushed in

yes engine cranks with both bcus installed

So, as there was an interruption in that harness between C0286 and BCU you must make sure there isnt some other path interrupted too, with BCU connected and ignition on make somehow using a needle to measure voltages from behind in the plugs as follows: negative probe in C0660 - 11 positive to C0660 - 1 and 3 ,

also confirm that before you rewired the K line you got the same messaage with hawkeye when connected to BCU ? the gist is that if the BCU has all the inputs and continuity to OBD there's no reason for a communication failure.