In the black box under hood there is a 20 amp fuse labeled ECM B. I was told it is tied to the fuel pump and computer. Earlier this summer it kept blowing the fuse, I would replace it and be on my way. Afew days later it would blow again, so I ask one of your experts what it could be. I was told it was a short in the fuel pump itself. I put it off for awhile knowing it was a big job. Got tired of blowing fuses so Finally I changed the pump. All went well and I have driven the truck 4 or 500 miles since. The other day it blew again, only this time, it will not take a fuse, it blows right away. Any idea's?
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The fuel pump relay is in the engine compartment fuse/relay box . The relay on the control side is given B+ from the PCM - engine computer . The load side (fuel pump ) gets B+ voltage from the ECM B fuse 20 amp - location ,under hood fuse box. GM Fuel Pump Relay Testing
In the under hood fuse box ! Fuse # 12 it's a 20 amp fuse . There is also fuel pump relay . Located in the same under hood fuse / relay box . #57 relay . The relay is computer controlled ! If the fuse is good you may want to watch this video on testing GM fuel pump electrical circuit . GM Fuel Pump Relay Testing
What engine ? Could have a relay or could have a fuel pump flow control module ? Two different set up's ! What is the RPO # (LY6) This one has a relay , and it would be in the under hood fuse / relay box . Would be maked on the inside of the fuse box lid . The one with the fuel pump flow control module will have two fuse's in the under hood fuse box 21 & 56 #21 FSCM 20amp fuse & 56 ECM- IGN. 15amp. . I know the one with the fuel pump flow control moduel has problems because of where they put it , under the vehicle near the fuel tank . Water an road salt an corrosion ,caused damage .
Raise the hood of your car and look near the battery for a black, plastic box. Unsnap the lid and raise the cover. On the inside of the lid there should be a schematic of the fuse orientation, and inside this box there should be an array of circuit breakers, fuses and relays arranged according to the schematic. One of the small, black relays is likely to control the fuel pump. Near the relay there is also typically a red, 10-amp fuse labeled "FUEL," "F/P" or "FUEL PUMP." If not, check under the dashboard.
If its under the Dashboard
Use a flashlight to look under the dashboard. In most cases, there should be a lower cover to access the fuse panel. Remove the cover with a small screwdriver and pull the lid off of the fuse panel. On the inside of the lid there should be a label that identifies the fuse arrangement, similar to the label on the power center under the hood. Look for the same lettering that designates the fuel pump fuse. If the fuse is not there, look in the specialty fuse panels.
i would check wire harness for bare wire but first i would look under that massive fuse box under hood, i kept blowing air cond relay and i traced it back to corroded connection on that fuse. not saying this is it and i hope it is that simple for you. other than that research exactly what the ecm-1 CONTROLS and search,test,grounds those systems. If i can come across any other symptoms i will forward them to you.
Did you check your fuel pump relay and related fuses to make sure no fuses were blown? Passenger side under-hood electrical center shows # 3 fuse 20 amp fuse controlling fuel pump and ECM. Also #12 is also Fuel pump relay in Passenger side under-hood electrical center. These would be the first things to check.