check engine light

[rww930]

94 6.5 dually...I've been getting the ses for several months when I get to 65mph. Not 60, 65. If I slow down, it goes off. The shop said it was a no fault code (I think) and not to worry about it. There are no symptoms.

My gas mileage blows at 11 per but it's always been that way.

Thanks for the help.

[grancito]

did they say it was a code 12?, read it yourself, open a paper clip and connect the two top right contacts of the plug to the left of the steering wheel, under the dash. Turn ignition switch on, DO NOT START ENGINE. Count the blinks of the SES light. If it blinks once then twice and repeats, then there is nothing. Let it make three repeats and see if there is a change. Mine if it has a code will only blink the code. When you have seen a code, press brake and accelerator together for 15 seconds, then switch off, then remove the paper clip, the codes will be deleted.