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the Sunday before memorial day i was towing a small 2 place jetski trailer and got this code, and iv gotten when ever im towing on the highway ever since.
code 556- fuel pump relay primary circuit fault.
any ideas??? it throws it on both the front and the rear tank.
iv also noticed that the truck will stumble a vary little bit while accelerating aoud town, i dont know if this is related or if its just a result of low grade summer fuel and hot weather.
Im guessing the relay is going but then why wouldn't it throw it when unloaded. and if a relay is gone then the pumps wouldn't work at all.
Sounds like you are loosing power to the pump curcuit intermittently.. could be a bad ground or flakey relay. I had the main power wire corrode completely off of the pump relay on my truck, might be something to look for.
ill check all the grounds, everything else is working fine.
but since you mentioned grounds i just thought about this, i had a bad ground connection on the battery for a while, i fixed the ground the other day, then when i towed a vary small amount(empty single place jet ski trailer) today it never light up the CEL.
could this have been the culprit?
But im gonna check all the connections and everything just to make sure.
where is the relay at, the underwood fuse box? i hadnt had a chance too look into it vary much yet. the trucks frame and wiring is in outstanding shape and i hadnt ever had a corroded wire before, but theres always a first.
thanks for the idea.
any other ideas?
do yall think the ground was the problem?