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MG MGF Technical - Technical question regarding dead car harness swap

Have changed loom/harness in a 2001 F and have kept all electrials ECUs /alarms i.e. - only thing not kept is key & ign /door locks! FOBs and the black unit around the ign locks is also changed! But it wouldn't start afterwards, looks like a immobiliser issue since its totally dead while alarm & central lock seems to work properly! Is there any other issues we have overlook, might we need to change driver doorlock as well? Car were running prior to the change as were the donor and we are shure we haven't mixed any of the units.
RN Roar

2001 MGF. Hmm - I presume that this will have a Lucas 5AS immobiliser, and in which case, your life is going to be much easier than the later immobilier fitted to latter TFs!

One thing though that is not entirely clear from your post - have you put the donor 5AS in the car, and retained the car's original MEMS? Or have you put in the donor car's 5AS and MEMS engine management? If the former, then this is the problem: MEMS is coded to the 5AS, and if another is fitted, it will be receiving the wrong 'message' from the 5AS. MEMS can be re-coded on Testbook however. Or, likely easier, will be to keep the 5AS and MEMS in a pair - either the donor or the recipient's original ECU pairing.
Rob Bell

Yes, correctly it has the Lucas 5AS immobiliser and to clarify, we have taken the harness with all electricals and moved over to another shell(also the engine & gearbox / rear subframe package). So all original units like MEMS & 5AS and key fobs have followed, even FOB anntenna on ignition switch! BUT we have not changed steering collumn, ignition switch & door locks! Before we started to mount interior we wanted to check out if the ign. would turn the engine but it doesn't! Is there any issue we have overlooked, the alternator is not connected yet otherwise everything should have been connected! So there should be no missmatch between 5AS & MEMS, there is probably a easy thing we have overlook and just thought there might be someting with the doorlocks?
RN Roar

Just a short Q on the matter, when immobiliser don't accept (none starter) will engine turn but not fire,, or just totally dead as not act to key turn at all??
RN Roar

Pretty sure the immobiliser will prevent the starter motor from spinning if it's still armed.
I can't think of a reason you'd need to use the original door lock, they're 'dumb' devices.
I've seen very odd problems with the 5AS unit clear themselves with a full power-down, i.e. overnight. Equally, as the voltage & current are so low on those circuits a thorough clean of all contact with electrical contact spray to remove surface oxidation is well worth doing.
bandit

>> Just a short Q on the matter, when immobiliser don't accept (none starter) will engine turn but not fire,, or just totally dead as not act to key turn at all?? <<

You'll get an audible dual-tone beep alarm, and the engine will not turn over.

If the engine is turning over, check to see whether you're getting fuel, as I wonder whether the inertia switch may need resetting (may have tripped on its removal from the donor vehicle to its installation in the recipient).
Rob Bell

WELL,, at last we found the fault! After 2 more afternoons we changed all parts for the system -5AS
/transmitters and fobs back from the other car, and it acted exactly the same as with the first set mounted. We followed all resetting sequences and ALARM worked correctly on both, but dead. We came to the conclution that there had to be someting wrong in the engine bay. After checking it twice we found the connector on the engine management relay not properly inplace, its the relay hidden behind the bracket for the main ECU. And it started at once!
RN Roar

LOL - it's always something simple, but annoying to identify isn't it?

Glad to hear you've got the car running again, and thanks for letting us know you got it solved! I've done the same thing (transplanted a wiring loom from one car to another) for Project Shed, so if I encounter problems, I'll know where to look!

Cheers
Rob Bell

This thread was discussed between 26/02/2010 and 02/03/2010

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