Hello,
Hope I have the correct thread, new to the site. I have a 2004 XF that once it reaches operating temp and is idling the car dies. Started out to being intermittant then proceeded to get worse with no hard fault registered (i.e., service Engine light would come and go). Now the car doesn't want to start until there is a significant lowering in the engine temp. Have received a constant Service light with P0412 code. Have been reading a number of posts with this issue and all point at the Relay Control board, I have pulled the Relay Board and have done a visual inspection and all solder joints look good and all the relays look good i.e., no pitting or corrosion. Started the car today and let run heard the Air pump running for a few minutes then shut off, car continued to run, then when the engine was just about at operating temp I heard the air pump kick on for just a second or two and shut off, about a minute later the engine died and would not start. Anyone have any feed back on this. Just dont want to spend money on the Relay board to find out it isn't that.

 

Yo Bill.

Redo the three joints pointed out in the RCM thread.
It's free and might get you back on the road.

 

Hey there tighd1 on,
Thanks for the info, I have pulled the RCM thread that were talking about and found some photos showing the RCM and 3 solder joints in the upper left corner of the board. When I inspected the board i saw no solder joint that looked even close to those, so I went out and bought myself a magnafying glass, my eyes are getting old and tired..ha. I do have a couple test that I want to run on the switchover soloenoid that are listed in the service manual for P0412 basically step 3 and 4, since I dont have a scan tool thought I would try that test. But definitly gonna look the board over better. Thanks so much will let you know what I find out.
Oh by the way since owning the vehicle this is the first problem, no fuses have ever been replace, which brings me tomy question in the RCM there is a fuse block, everything I see is a 15 amp plus the 40 amp. on my RCM there is a 20 amp fuse in location 3 labeled Engine Control 1.
Thanks again

 

This photo shows the fuse layout, it is the same is this spare one and the one in the car. Maybe no help to you but ...

 

Your Photo looks Identical to my RCM and the one labeled #3 in your photo is the one in question. Pulled the fuse out and there are contacts inside the mounting area.
Have looked at the solder joints under magnafying glass but cant tell taking it to work and going to the lab and put under a microscope that we have for checking these things out. I will say they do look a little ruff, and the resistor joints dont look to great, but cant tell if they are loosing contact or not.

 

Hey Bill....resolder the 3 joints....I won't say if this has happened once it has happened a thousand times...but it has happened at least 20 times....

 

Hey Everyone,
I want to thank everyone for all the help. I took the RCM to work and re-soldered the joints and few others at the same tiime. Put the RCM in the car and the problem has gone away. You guys are the best!!!!!!!!!

Thanks so much, and the little woman thankls you since it is her car, nd she has had to drive the truck while I rode the motorcycle to work. Cant thank you all enough.

 

Thanks are not required ......... send money instead.

 

I spoke to soon, took the car out last nite and it has starterd doing it again. Had to have it towed back home.