Played good Samaritan last week and offered to jump start a car. Well no good deed goes unpunished I guess. Said ***###$$$$ decided to check if I had the cables hooked up by shorting the other ends. Haven't driven truck since then.

I tried starting my truck this morning and the batteries are dead, hook up cables to another vehicle and still nothing. Let it run for a while and still won't start. I notice this switch/reset button next to the battery so I push it. Boom truck starts? Anybody know what this is?

 

It is a safety switch to electrically disconnect the batteries while you have the hood up working on it.

 

Thank you. Would be nice if they had that in the owners manual or diesel supplement. Now to figure out if the batteries going dead are a coincidence or something is screwed up.

 

Sounds like it may also double as a circuit breaker?

 

That switch failed on my 2011 truck. The only symptom was that the remote start wouldn't work. Apparently it's just a safety thing that won't allow the remote start to work when the hood is open.

I really don't think it's tied into the problem you are experiencing, I just by passed it with a jumper and I never had any issues, nothing like you describe.

There may be a circuit breaker somewhere else though that you may have tripped.

 

The only thing protecting the batteries/vehicle is a 275 amp fuse in the battery junction box under the passenger side battery. There isn't a circuit breaker nor a battery disconnect while the hood is up. If there was, nothing would work while the hood is up. If there is, don't tell my truck. I often work on various items including having the engine running with the hood up. That switch in question is for the alarm. Open a door or pop the hood with the truck locked sets off the alarm. If the truck is in remote start mode (engine running, key out) opening a door, popping the hood or even stepping on the brake (required to shift gears) shuts off the engine and sets off the alarm. If the truck is locked and you use the key to unlock the door (not the remote), opening the door sets off the alarm. Some folks have even installed a switch on their tailgate (expensive if stolen) and tapped into that switch to set off the alarm if someone tampers with the gate. My guess is that when you shorted the jumper cables together momentarily, you created a voltage spike that played havoc with the electronics. With upwards of fifteen computers onboard, creating spikes like that is not in your best interest. I'm glad you were able to get your truck running again.

 

Installed two new Die Hard Platinum batteries and everything seems fine.
Charging 14.4V, so it looks like it was just a coincidence that the batteries crapped out after the short circuit.

 

The only time I've ever jumped off another car with my truck, I left the ignition off, keys out and doors closed. With two big batteries, I didn't feel the need to tie in my electrical system to theirs. It worked like a champ and started their vehicle immediately with no problems on my side afterward. I also have heavy gauge jumper cables to get max current.

 

I usually do the same, I didn't have cables with me, he had cheap small gauge cables. Tried with my truck off no luck, so I started my truck and that is when he took the cables off his car and touched them together.

 

Well I know that when I have my hood up I am not able to start my truck with the key or the fob. And Double-Trouble I would never recommend touching the cables together... bad things tend to happen when you do.

 

Trust me I know better. It was the person I was trying to help out that did it.

 

That switch is basically equivalent to a door switch. It doesn't interrupt any electrical systems... in fact I poke it when I have the hood up for a while just to wake up the BCM, because it will shut off all vehicle lights after a timeout. The PCM is aware of its status to prevent remote start from occurring as a safety measure.

 

I can start mine with the hood up.


If you are going to jump another vehicle now a days I recommend two ways only.


First a portable jumper box.


Second would be using very heavy cables so you don't need to run your truck. If you have to run your truck shut off all the electrical stuff you can. HVAC, Radio and anything else you have plugged in.