2008 Ford F-150 Owner Seeks Help with Electrical Gremlins

F-150 won’t start with a dead battery, but when the charging box is connected, the problems get worse.

The electrical system of the modern Ford F-150 pickup is incredibly elaborate, allowing everything to work in conjunction, but when something fails, it can be a nightmare to diagnose the exact problem. Forum member “tybo7” recently ran into some electrical gremlins that he couldn’t fix, so he turned to the forum for help.

Not surprisingly, other members of the forum had plenty of ideas to solve the problem, including tips to help diagnose the issues and possible causes of the condition in question.

The Introduction

When the OP first posted the thread detailing the problems with his 2008 F-150, he provided the following explanation of what was happening.

“2008 F150 Lariat 4×4 5.4 serious electrical problem. Overnight, my battery discharged and when a charger is connected – without the switch on – the tach vibrates and needle moves to 5k rpm and the fuel pump clicks. When I started pulling fuses and relays to troubleshoot, it got weirder. By pulling fuse F40 (for DRL, light switch, and body security switch) and then pulling R02 Accessory Delay relay, the fuel pump stops clicking but then the Elec Throttle Control starts chattering. I’ve never seen anything quite like this. Any help is appreciated.”

F-150 Community Responds

The first person to reply was “glc”, who offered the simplest solution to a charging problem.

Disconnect the battery, charge it, then reconnect it.

That input was reinforced by “joe1951”, who elaborated on the charging issue.

If your battery isn’t bad then this should cure the problem. The problem you describe is due to the fact that MANY of the electrical systems in the truck are still connected to the battery and still “running” even with the truck turned off and that low voltage from the discharged battery is causing them to behave erratically. Disconnect them battery, charge it and then reconnect it when it’s fully or nearly fully charged and everything should be fine. As long as the battery isn’t weak.

While “Labnerd” believed that the computer system of the F-150 could be at fault.

My money will be on the PCM being toast.

When the OP installed a new battery, he feared that Labnerd may have been right.

You may be correct. I installed a new battery and the electrical system appears to be non-functional.

To which Labnerd offered some more humorous insight on his idea.

Well before you declare me intelligent and ruin my perfectly bad reputation, I’d also be looking at the Vehicle Security Module. It controls the remote keyless entry, power locks, the electronic automatic temperature control, and the battery network. It works like a GEM only you don’t have a GEM on your truck. But if the VSM isn’t right, nothing in the electrical of the truck will be right. I’d take a look at that before spending any bucks for a PCM. Now for the bad news. The VSM is located behind the backrest of the rear seat. Best of luck getting that apart. When I removed mine I seriously considered dynamite.

The Problem is Solved

Fortunately, just three days after the OP started his thread, he posted that he had figured out the problem. Upon finding the video below from the FordTechMakuloco YouTube channel, the OP found that all of his issues were caused by a bad fuel pump driver module. Once that was replaced, the F-150 was back up-and-running, so for anyone experiencing a similar issue, we have included the video below.

If you have a similar problem and the fuel pump driver isn’t the issue, click here to head into the forum to get insight from the members of the community.

Patrick Rall

"Before I was old enough to walk, my dad was taking me to various types of racing events, from local drag racing to the Daytona 500," says Patrick Rall, a lifetime automotive expert, diehard Dodge fan, and respected auto journalist for over 10 years. "He owned a repair shop and had a variety of performance cars when I was young, but by the time I was 16, he was ready to build me my first drag car – a 1983 Dodge Mirada that ran low 12s. I spent 10 years traveling around the country, racing with my dad by my side. While we live in different areas of the country, my dad still drag races at 80 years old in the car that he built when I was 16 while I race other vehicles, including my 2017 Dodge Challenger SRT Hellcat and my 1972 Dodge Demon 340.

"Although I went to college for accounting, my time in my dad’s shop growing up allowed me the knowledge to spend time working as a mechanic before getting my accounting degree, at which point I worked in the office of a dealership group. While I was working in the accounting world, I continued racing and taking pictures of cars at the track. Over time, I began showing off those pictures online and that led to my writing.

"Ten years ago, I left the accounting world to become a full-time automotive writer and I am living proof that if you love what you do, you will never “work” a day in your life," adds Rall, who has clocked in time as an auto mechanic, longtime drag racer and now automotive journalist who contributes to nearly a dozen popular auto websites dedicated to fellow enthusiasts.

"I love covering the automotive industry and everything involved with the job. I was fortunate to turn my love of the automotive world into a hobby that led to an exciting career, with my past of working as a mechanic and as an accountant in the automotive world provides me with a unique perspective of the industry.

"My experience drag racing for more than 20 years coupled with a newfound interest in road racing over the past decade allows me to push performance cars to their limit, while my role as a horse stable manager gives me vast experience towing and hauling with all of the newest trucks on the market today.

"Being based on Detroit," says Rall, "I never miss the North American International Auto Show, the Woodward Dream Cruise and Roadkill Nights, along with spending plenty of time raising hell on Detroit's Woodward Avenue with the best muscle car crowd in the world.

Facebook   Twitter