91 ECM'B' fuse blows and ECM P/N help (long)

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Posted by Donoburb ( on 23:28:23 01/08/08

I have a 91 r2500 w/454/4l80E/4.10 which is my TV for a 34' AS trailer. Mileage is less than 120K and the truck is in excellent shape.

My problem is the ECM'B' 10Amp fuse will blow intermittently. This circuit is hot at all times and there are times I cannot replace a blown fuse (without the new one blowing, too!) even with the vehicle off. I have, with the help of another person, tried to shake, wiggle and move the wiring to attempt to locate the point where the wiring is shorting. No luck.

I have the factory wiring manual for the truck and the entire circuit is #440. Wire is direct from fuse to ECM with two switched circuits: oil pressure and fuel pump (designed to turnoff the ECM if either switch opens). The two circuits are not in the picture when the ignition is off. With the engine off the only things 'hot' are the wires to the switches and the ECM itself; as far as I can tell from the wiring diagram.

I would like some additional insight. Could the ECM be causing the failures due to heat? This does seem like a heat related failure as right now the fuse is in place and the truck runs. However, I know that it will blow after a run, but I cannot predict when. Much like a capacitor in an electrical appliance that fails when heated then resets when cooled. Can't risk towing like that.

Does anyone know the correct P/N for the ECM in this truck? Again it's a '91 R2500 2wd, 454, 4L80E, and 4.10 rear. I would entertain the idea of a used, correct part number ECM as a troubleshooting replacement.

It's been awhile since I've been on the board, but I know you folks can help. I need my reliable truck back!!

Take care,


N.B. To e-mail, replace the word 'at' with the proper symbol @!!

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