I have a p1291 code on my 2001, did the searches. Came up with three posts on the code, but no answer on what fixed the issue. No temperature rise seen from intake air heater is the discription for the code. I was going to replace the relay in the heater circurt tomorrow. But I would rather get feedback on fixes from those that have addressed this code in the past. Anyone every have this code come up in their trucks, if so, what did you do to fix the codes? Plus, is it safe to run the truck with this code?

Thanks in advance/ BRO

 

Do a couple of tests and see if the grid heaters are working. Test for voltage at the grid heaters when someone turns the key on. If the grid heaters are working, i would look into an IAT.

 

Thank you tractorguyacb for your reply. I will do a little more research and try out what you advise me to do. BRO