2010 F150 (4.6L) Brake Booster Vacuum Code

[the_twig_187]

2010 F150 (4.6L) ABS code (C109D = brake booster low vacuum detected)

Diag thus far:

hooked up vacuum gauge and “T” off of brake booster hose, drive vehicle at 80 kph and observe vacuum gauge reading 3 in/hg when at steady cruse on a flat smooth road. (Vacuum reading start idol is around 20 in/hg

hooked up smoke machine to intake manifold to check for leaks and no external leaks were found.

no other vacuum related code were stored in the PCM and vehicle does not seem to run abnormally at all other then the red brake warning light coming on and “check brake system” message on IC when the vehicle is driven at a steady cruse on flat smooth roads.

any advice on how to proceed further would be greatly appreciated. Thank you very much

chris 

[8WA Sman]

Chris,

How about a Vin or 2v or 3v or 4x4? This would all help to assist.

Any brake pedal concerns?

What about a faulty check valve?