Tractor Posted January 3, 2005 Report Share Posted January 3, 2005 I had a check engine light on my OBD-I GMC truck. Code 54. My manual says that is for the fuel pump relay. Is the relay the most likely cause or would it be the fuel pump?? Evan Quote Link to comment Share on other sites More sharing options...
Alex1647545498 Posted January 3, 2005 Report Share Posted January 3, 2005 Usually a service manual would be able to instruct you on how to test the relay. You can also supply direct power to the fule pump to "hear" if it comes on. You should be able to determine the problem with those methods. Quote Link to comment Share on other sites More sharing options...
Dave1647545494 Posted January 4, 2005 Report Share Posted January 4, 2005 switch it with a good relay and see if the light goes out. its probably sending the wrong voltage to the pump Quote Link to comment Share on other sites More sharing options...
Tractor Posted January 5, 2005 Author Report Share Posted January 5, 2005 light is not on. truck stopped on the highway. check engine light came on and then wife started it back up and drove it home. I pulled the code from the computer. hasn't had a problem since. I'm guessing it was the really nasty weather we had monday. Evan Quote Link to comment Share on other sites More sharing options...
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