signal lights

you probley have a bulb burned out on the blinker bulb check all with blinker on if no bulb is out the flasher is going bad,but i guess a bad bulb,

burnt out signal bulb...walk around ya truck and check....voltage is incorrect and is telling you flasher a bulb is burnt out.....l.e.d.  bulbs will do this ...you will need a voltage regulator to splice into your l.e.d. lights.....good luck