I never fooled with the 20 amp fuse that is under the hood of my '91 740 with Rex-Regina engine management. I always assumed it provided power to the ECY (computer)like the one under the hood of my '89 240 with Bosch LH 2.4 engine management.

Today, just for fun, I pulled the fuse on my 740 while it was running. I was very surprised when Regina just kept chugging along. If this fuse doesn't power the ECU, then what does it do?
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Andy in St. Paul. '89 244 153K mi, '91 745 Regina 202K, '88 244 184K

ABS maybe? Did the 91's have ABS? My 94 940 Regina does not any extra fuse ( that I know of) in the engine compartment, but does have an extra ABS fuse somewhere under the dash console, according to the glovebox manual.
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Gary Gilliam Sumerduck VA, '94 940 na Regina 160k '86 240 190k

740s were available with ABS at least from 1990, but my '91 doesn't have it and never did. This fuse is in a reddish wire that comes off the positive terminal of the battery (just like the one on the Bosch cars). It is over in the vacinity of where the ABS unit would mount if I had one, but the wire continues back into the engine compartment from there, so it doesn't look like an unused ABS item. I didn't trace the wire back to try to see where it goes, but I will when I have time to kill.

BTW, I am the third owner and the first two were not people to do any mods of any kind.

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Andy in St. Paul. '89 244 153K mi, '91 745 Regina 202K, '88 244 184K