I've been fighting the P1291 code over the past few weeks, which is "No Temperature Rise Seen From Intake Air Heater". I went through the protocol check list to determine what could be the problem but everything seemingly checked out. I could have overlooked something but nonetheless.....

Without going into a long drawn out post about what I've already done, I'd like to know who has already dealt with this code and what you did to solve it. Or should I say, what part did you find was faulty? Thanks guys.

 

I would check that all connections are clean and tight. Check the push on connections at the solenoid also, crimp them so they fit tighter when pushed on to studs on solenoid. Check ground wire at the heater grid make sure it is tight and connections are clean if equipped.

Here is diagnostic test procedure maybe of some help.

 

No personal experience, but it sounds simple enough. Dirty or faulty IAT? Check voltage at heater grid connections...

Guess it's time for a long drawn out post.

 

To do a quick test on the grid heaters, I would always put an amp clamp around the two cables right at the preheater, then turn on the key with the engine cold. The two elements draw about 90 amps each, so I would expect a reading of around 180-200 amps if both elements are working properly. It was fairly common to see only half of that value and I would know right away that only one of the grids was energized. It always turned out to be one of the two relays having burnt up contacts not letting the current through.

 

Found it.....
The ground cable from the grid element to the manifold had a bad connection and was causing an intermittent ground issue.

Here's what I found. Because I dont think I could have found this little cable anywhere local and the corrosion was on the exposed end, I shortened it and re-crimped it and sealed it.

 

Nice find!