The check engine light decided to come on yesterday on my truck. The local Autozone guy told me it was giving an error code P1491. Any clue what is causing this? Truck is a 2002 Dodge Ram 1500 2 wheel drive 4.7L auto

 

I did a quick search on google, and found that it is a "Radiator Fan Relay Circuit". Since the Ram's only have one electric fan, I would assume it has something to do with the condensor fan. So you should only need that fan when using your A/C or Defroster. I don't know the fix, I haven't had this issue.

 

Check fuse 39 in the PDC. The condenser fan fuse (#39) in the power distribution center may open leaving the
condenser fan inoperative. This may be caused by a condenser fan with excessive current
draw or by water collecting in a trough in the fan shroud and freezing in cold weather,
which can prevent the fan from turning. See TSB 08-002-03. Their is a redesigned fan and flash for the PCM.

 

Junior5290 Thanks for your input. I did find the fuse to be blown. I replaced the fuse and reset the computer and light is out for now. I didnt try running the defrost yet though. Funny thing is I had the dealer make that fix this past summer. They changed the fan and housing, etc to fix the supposed problem. I wonder why it went again?

 

More then likely they didnt reflash the PCM. The flash changed when the fan would come on based on outside temperature.

 

I just fixed this problem today! My Air conditioner was only blowing cold at higher RPMs so bought a charge can with gauge. WHOA! the low pressure side was too high to add refrigerant! Got to digging around in the fuse box and found the 25 fuse burnt to the fan. A/C is working perfectly and pressure is right on. The guys at Advanced Auto Partstold me the code was a vacuum leak or failure in the Aux emmision controls (evaporator system) so spent an hour checking vac. lines under the truck to no avail. I still need to reset com. to get rid of the engine light.