2016 F-150 XLT: A couple of months ago, I discovered that some sort of critter chewed through the plastic vacuum line going to my brake power booster. The result was almost no brakes. I was able to quickly fix that, but in the process discovered that the same critter must have chewed through a line that's associated with the gas gauge. It now shows empty, no matter what. I performed the gauge test and confirmed that the gauge itself is fine, so it's just a matter of finding root cause.

Yesterday I discovered that the controls for heat, volume, defroster, etc. are no longer functioning. Also inoperative is the driver and passenger side windows. The rear windows still work. The remote fob no longer locks/unlocks the doors either. And finally, the airbag light is always on. Where to start is the question - although I will start at the fuse block to see if anything has blown.

This is a bummer since it's the coldest part of the year and not exactly conducive to debugging electrical issues. If anyone has any suggestions, I'll definitely take them. In the meantime, I'll do some research and see if I can find common circuitry that might lead me in the right direction.

I can only imagine what a dealer would charge to diagnose and fix these issues - hopefully I can do it all myself.

 

Start by looking at the connectors on top of the driver side wheel house. It sounds like the MS-CAN bus has been broken. This area is a favorite spot for rodent damage. The MS-CAN bus passes throught C327 twice (two MS-CAN+ wires and two MS-CAN- wires).



The fuel level gauge circuit passes through C316.

 

Thanks. As soon as it warms up a bit, that will be the first area I'll check out.

 

The other day I went to a friend's shop and we did a scan of the codes. There were MANY, such as:
Fuel Level Sensor (probably a chewed-through wire)
AC clutch signal
Lost communication with HVAC control module
Lost communication with front controls interface module A
Lost communication with door control module A
Lost communication with lighting control module rear B

There are more, but you get the idea. I need to l locate module A - is that behind the dash on the driver's side? Perhaps the critter that chewed through the vacuum line for my brake booster got inside and inflicted more serious damage. With so much messed up here, I think I should start with module A.

Suggestions or advice?

 

Everything you are having communication problems with uses the MS-CAN bus for communication. Knowing you had rodent issues around the brake booster I would concentrate on investigating rodent damage to the wiring running in and out of connector C327. The MS-CAN bus has four wires passing through this connector which is located just below and in front of the brake booster.

 

With warmer weather, I was finally able to dig in to see what might have been causing the airbag light, no front power windows or mirrors, no HVAC control, etc. Upon much closer inspection, I could see some damage to the outer covering for the wires coming from C327. Once I carefully removed the wrapping, I found one wire completely chewed through and another one hanging by a thread. I was able to solder and heat shrink them, then re-wrap with some special wiring harness tape that I use for motorcycles. Fired up the truck and everything (except the gas gauge, will cover in a new thread) is working again!

52merc - thanks for your help and suggestions. I'm 98% back to normal with this truck. You are the man!

 

Last intake air filter change, I found a nice stash of acorns in the bottom of the box. Still not sure how half of one ended up in the pan, found while "panning for gold" after an oil change?

 

Here it is, months later and the gas gauge is still not working and the check engine light is on. I finally dug in this morning and closely inspected connector C316. I had to unwrap it and bingo, I found the blue/pink wire severed. The green wire also had three chew marks through the insulation. I repaired both wires by soldering in short lengths of new wire. Reconnected everything, turned the key, and still the gas gauge doesn't work and the check engine light is on! Is a hard reset necessary to bring this back to life, or am I missing something else? Everything else in the truck works fine now, so I was sure that the severed wire was the culprit. Any suggestions? Thanks.