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I’ve had a recurring P0299 code for about the last 35,000 miles. I’ve had the truck in the Ford garage three times already for it and they can’t find any problems. Currently the engine light is on and P0299 is showing on my scanner.
Truck: 2012 F350. 112,000 miles with extended warranty to 135,000. Engine and exhaust are stock with no modifications.
What I’ve done: checked the CAC for any leaks or breaks. Can’t find any. When I took it apart to check for cracks I was surprised at the oil and gunk built up inside. I’ll attach a photo so you guys can tell me if it is normal.
I have another appointment scheduled with Ford, just trying to look for solutions since they have been unable to find anything.
Sounds like you have a loss of boost pressure. Maybe bad o-ring on the cold air tube or a crack you can't see or even the inter cooler is leaking.
From the MY2015 OBDII.
Underboost Monitoring
The underboost monitor works in a similar fashion to the overboost monitor by comparing the desired vs. actual
measured boost pressure while in a specific range of closed loop boost pressure operation. If the boost pressure
governor deviation is greater than the calibrated threshold for 7 seconds, a fault is detected and the P-code is set.
The closed loop monitoring window is defined as any inner torque above 50 nm, and any engine speed above
1500 rpm. The threshold limit is wider for the underbooost monitor due to transient boost system response,
compensation for boost pressure lag, and short term (1-2 second) momentary torque truncation when air path
torque is kept high, but fueling is limited for component protection.
This diagnostic will detect a gross air path leak such as the turbo discharge or CAC discharge tube being blown off,
major pre-turbo exhaust leaks, or a turbo slowly responding or stuck in the open VGT position.
Cold side, CAC tubing, well known for failing. I decided to upgrade mine. Actually bought it when on holidays and on the way home up our notorious Coquihalla Hwy blew the stock plastic tube. Had to jump into the back of the truck and unpack he new CAC kit and install part of it with a lot of tuck tape to get me home. Little unnerving fixing your truck on the side of a very busy highway with a trailer connected!
I reexamined the cold side cac tube and found the o-ring showed clear signs of blow by on the bottom portion. The ring also was malformed at this spot whichh didn’t let it mate properly to the metal surface.
I bent the plastic o-ring back down and reinstalled it so it was on tight. The code has not reappeared and the truck is building a full 20 lbs of boost now.
A new cac tube will be placed on the truck for a permanent fix.
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