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Premium Member
1970-1995 Range Rover Classic
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425 Posts
Discussion Starter #1
I have a BECM and M5.21 from the same car here, a 1999 NAS 4.6

Have unlocked the BECM, enabled EKA, disabled alarm, disabled immobiliser.
Same security code in both Bosch M5.21 and BECM.

Still comes up with the same.

put his Engine ECU in another car, starts.
but won't talk to his BECM.
So I put in another logic board and I am still getting the same. :roll::oops:

Any ideas would be great. I have also posted this in the Blackbox forum
 

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Registered
1995-2002 Range Rover P38A
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1,355 Posts
As you have SM035 why not back up the settings for both cars, then swap the BECMs over; a 3 to 4 hour job I would have thought.
If the problem still stays with the car it must be the wiring or connectors.
 

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Premium Member
1970-1995 Range Rover Classic
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425 Posts
Discussion Starter #3
both ECUs are on my desk, have connected it all directly. The other car is not here. I have done some swapping. will try again with another car. I thought the error should clear with the black wire on C0637 connected to the BECM, both on diagnostics?
I might be wrong though and I will happily listen to somebody wiser than me
 

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Registered
1995-2002 Range Rover P38A
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129 Posts
Could it be that everything you are doing to BeCM and ECU is right, but the wiring that connects the two is faulty on this particular truck?
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,159 Posts
Is the passive immobiliser turned on in the BECM settings?

That 'fault' in the Bosch ECU will show up any time the BECM is not sending the code, or it's incorrect. So if ignition isn't on, or passive immobiliser has kicked in - things like that will stop the BECM from sending the code, and have the ECU show a fault.

EDIT just read the immobiliser is off...

Does his logic board allow a different ECU to start? if not, then it could be a fault on the logic board - I've had a couple over the years where the process of soldering onto the board to attach the SM035 kills something on the board which is involved in sending the code to the engine ECU.

Though you mention you've tried another logic board too.... what version was the replacement board? earlier logic boards - although you can program them as 'motronic' don't actually do anything as the firmware version doesn't have the motronic immobiliser strategy written into them - only later ones do... But if you set them to 'Late EDC' it will work, as they use the same immobiliser strategy. But running a Motronic petrol on a BECM set to Late EDC causes at least the temp gauge to read incorrectly as the sensors are obviously different resistance ranges... i'm also not sure if RPM is read wrong - because if memory serves the number of pulses per revolution sent by the engine ECU is different.... BUT it can be a useful trick in tested to use an older BECM to get a Motronic vehicle to start.
 

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Premium Member
1970-1995 Range Rover Classic
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425 Posts
Discussion Starter #7
Ok Marty. Thanks a lot that is an interesting piece of information.

I can't have killed them all or did I?

Yes just tried an early one and it doesn't work either although I did start a GEMS with it the other day.

No... I don't think so cause I unlocked another one last week.

But I definitely will try the diesel trick.



Enviado desde mi SM-A720F mediante Tapatalk
 

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Premium Member
1970-1995 Range Rover Classic
Joined
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425 Posts
Discussion Starter #8
Dear Marty,

I have been through 5 BECM s now.
The last one is one that works definitely.
But still the same error in the engine ECU.

A proven one , running another car for a week with AMR serial number doesn't work either. Not as diesel OR Motronics .

Pulling my hair out.

What could it be .. on the BECM I have the white 252 and the green one for the alarm wire connected, nothing else.

Motronics has all supplies and anti theft and diagnostics connected.

Lee in Oz says that us all I need

But maybe there is something else?

Enviado desde mi SM-A720F mediante Tapatalk
 

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Premium Member
1970-1995 Range Rover Classic
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425 Posts
Discussion Starter #9
SOLVED!!!

For all who come across that because they don't have the car present.

You cannot marry them up on the desk.

I put 3 different combinations in a 4.0 1999 P38 yesterday, all worked. What do you need to do?

Put the M5.21 into Discovery learn mode and done. this does not work on the bench. Don't ask me why. Blackbox says in its help file that this is only for Discoveries, well it helped me out once before on a p38. Maybe that is what unlocked vs locked BECMs want to see.

So if you want to try this, get a donor car.
I will keep working on my test rig till I find out what else is needed.
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,159 Posts
Re: SOLVED!!!

That is random - the discovery learn mode will only work on Disco motronic ECU's - as they learn a code being sent by the Disco BCM - whereas the P38 works in opposite - the code in the ECU is hard-coded and then you program the BECM with what it needs to send...

Maybe being powered up on the bench puts the ECU in a tizz... I would have thought that all you need to get it to talk on the bench would be power/ground/immobiliser wire, and maybe an ignition switched feed... very strange...

I might try it out on my bench with my BECM tester and a Motronic ECU when I get home, if I have time! I've tried and successfully talked to the Bosch Diesel ECU's on the bench with just a few wires connected... I wonder what's different with Motronic ones..
 
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