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Blew ECM fuse.

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Hey guys. Long story short. I have a 99 Sierra 6.0L. Battery completely died and in the process of charging the battery and trying to start it,  my ecm b fuse blew. I replaced it but now my speedo is pegged all the way to top speed and my gear selected icons won't indicate what gear I'm in.  I tried searching forums and the web but couldn't find anything on GM trucks for this issue. 


What am I going to have to do? Is it possible to reset the ecm? Am I missing another fuse? I only find ECM "B" and couldn't locate "A". I'm a bit lost with electrical.

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what you might want to try is disconnecting the positive terminal for about 20 minutes, being sure 1) to test your battery, 2) that the terminal and all connections regarding the charging system are clean and free of corrosion before installing a good battery, that is putting out 14volts. 


Also you said you blew an ecm fuse........ is that because the battery was hooked backwards pos - neg etc? Or was it because the battery was being charged in the truck and the charger was hooked backwards   or that wasnt the issue at all?


Sometimes when the fuel pump goes out it can blow this fuse, but likely your truck wont start after, unless the fuel pump is replaced.

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So the fuel pump did die, the truck sat for awhile until I had time to replace it, but by then it was dead. So after I charged the battery and tried starting it,  it wasn't firing off.  Saw that I blew my ecm fuse and just replaced it, as soon as I replaced it that's when my speedo pegged over and my shift stopped working correctly. 

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Update to the situation. After pulling ECM 1, ECM B, ETC, turning on the lights and disconnecting the battery for 20mins did the trick for the speedo. But now my truck still won't indicate neutral and won't let me engage 4x4 low. 


Is there something that I'm missing?

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