Why Does a Hatch Need Its Own Computer?!

Computers have been infiltrating cars for years. From engine management, to diagnostics, to antilock brakes, traction, and stability control, cars have become far more digital than analog over the years. In many ways this is good, but it can also go too far. Did you know that the Ford Flex has a separate computer just to operate the rear hatch? Neither did I, until I smashed one in a trailer accident and had a hell of a time making the replacement hatch work.

It all started when I was towing my local Society for Creative Anachronism group’s equipment trailer to a local event. Although my wife and I are the custodians of this trailer, this was actually the first time I’d ever towed it off our property since it was delivered to us last year. I was unaware that the trailer hadn’t locked onto the trailer ball properly until I heard the sound of scraping metal after the trailer detached from the car. I stopped more quickly than the trailer did, which smashed in the back window and dented the hatch of my wife’s Ford Flex. To say she was unhappy would be a gross understatement, and I don’t blame her one bit.

Smashed window and dented hatch

After a kind, educational, and free evaluation by our local Safelite AutoGlass – who also cleaned up all the broken glass they could reach and put plastic over the busted window at no charge – it was clear that we were going to have to replace the entire rear hatch. The damage that extended beyond the obvious broken window, making it difficult or impossible to replace just the window itself since the surrounding metal was bent, too. It wasn’t the news I wanted, but I appreciated their honesty about the difficulty and issues with the repair.

I got extremely lucky. A search on Car-Part.com showed me that LKQ ABC Used Auto Parts in nearby Leominster, MA had a hatch for a Flex. Even better, it was from a 2012 Limited with a power liftgate and no rear camera – an identical configuration to my wife’s car. It was burgundy, not silver, but whatever – it would get her back on the road again, and we could deal with the color later. A phone call confirmed that the part that was listed online actually existed in the real world, and a credit card secured the part in my name. Being unable to open the Flex’s hatch to put the replacement hatch in the Flex, I picked it up on our small flatbed trailer usually used for the lawn mower, motorcycles, and trash, with plenty of padding to prevent damage.

Built Ford ToughIt got home in one piece, and I immediately started fixing what I broke. With the new hatch acquired, it was no longer a problem if the old hatch never shut again, so just for fun I tried opening and shutting the old hatch a few times. Despite the crash damage and being slightly out of alignment, it still worked perfectly. “Built Ford Tough,” indeed.

I removed a couple of interior D-pillar trim panels, dropped the headliner slightly, unplugged all the wiring, and disconnected the rear window washer from a convenient plastic fitting. Then it was a simple matter of disconnecting the arm that opens and shuts the hatch automatically, the two struts that hold the hatch up, and removing the four bolts that hold it onto the hinges, and the old hatch was off. That was easy. I should have the new hatch on and working in no time, right?

Work in progress.

Yeah, that’s what I thought too. Installation is the opposite of removal, especially since the replacement hatch was off a Flex from exactly the same year with exactly the same options. With my wife and a friend helping to hold the replacement hatch in place, I bolted it up, attached the struts and the actuator arm, attached the washer hose, and plugged in the wiring harness. Problem solved.

Actually, no. The hatch wouldn’t latch, even though it moved freely throughout its range, and the automatic open and close function didn’t work. Online research taught me that there is actually a separate computer just to manage the rear hatch operation. Disconnecting, then reconnecting the battery would cause this computer to reset. This seemed to fix many issues people had run into of the hatch not opening or closing properly. So I did it. Now the hatch shut just fine. It just wouldn’t open again.

I wondered if the electronics in the replacement hatch somehow had to be synched with the reset of the car, like different components of a computer network. I took the Flex to the local dealer. A couple of hours and $93 later, they’d pulled three trouble codes – one for the latch mechanism, and one each for the left and right pinch strips. It would cost me even more for them to dive in further. I declined, knowing that I had a dented but fully operational hatch at home that I could mix and match parts from. (Oh, and they also informed me that the bumper-to-bumper no longer covered the hatch, because I’d replaced it myself instead of overpaying them to do it. Gee, thanks.) If these three components were dead on the replacement hatch, I could scavenge known-good parts from the original one.

Hatch removed

So that’s exactly what I did. But even after swapping those three parts for the ones from the original hatch, it still didn’t work. I could manually release the hatch by crawling all the way to the back of the Flex and popping the mechanism from the inside. But that wasn’t good enough for daily use. This needed to work correctly, like it did before I broke it, or I was going to have to build myself a doghouse to sleep in. Permanently.

Before bringing it back to Ford and emptying my wallet, my friend Jonah at FIX offered to see what he could do with it. He had a fancy Snap-On code reader that should be able to do everything that Ford’s did. So we took it to him for a second opinion. His computer pulled the same three codes as the Ford dealer, even after replacing those parts. We played with the physical alignment with the hatch and made it better, even though it already opened and closed manually just fine. We tried everything we could think of that made any kind of sense at all, but it didn’t solve the problem.

As a last ditch effort, I decided to replace the entire wiring harness with the one from the original hatch. It’s conceivable that a critical wire, like a ground, had been pinched and broken in the replacement hatch’s wiring harness, so once again I would swap in a part that I knew worked on the original hatch. I was quite thankful for the plastic panel removal tools I picked up a while back. One of them was perfect for popping off the numerous plastic pieces holding the harness to the frame of the hatch. That made short work of removing the harness. I wrapped each connector with painter’s tape and wrote where it plugged in so I wouldn’t forget.

Ford Flex liftgate wiring harness

Then it came time to attack the car. I removed the D-pillar trim again, dropped the headliner, went to unplug the harness… and felt with my hand a small socket, hidden out of sight, that had nothing plugged into it. I found a part of the hatch harness that wasn’t plugged into anything, and it fit. It was time to drop everything and see if that fixed it.

I shut the hatch, then disconnected the battery to initiate another computer reset. I reconnected the battery, then pressed the hatch button on the key fob twice. Lo and behold, HAL opened the pod bay door. Two more presses closed it. I made sure all of the other buttons – on the dash, in the back of the car, and on the hatch itself – also worked. Then I called in my wife to show her this fully armed and operational battle station.

Fully armed and operational battle station

As with the original smash-up, I take full responsibility for failing to plug in the harness properly. I was rushing, had never done this before, and missed the second connector, completely out of sight and out of mind above the headliner. But it’s not like the Ford dealer did anything except plug in their computer and tell me “it’s broken.” Jonah couldn’t fix it either, but at least he tried everything else he could think of to fix it in good faith, and it’s not like I had the spare wiring harness at his shop with us. He was genuinely glad to hear I’d fixed it myself and didn’t need to bring it back to him.

My biggest issue, though, is the needless computerization of features and basic functions that have no need to be handled by a computer. A simple key lock and cable release worked for many years to open and shut doors and hatches. Why do these need computers? It’s just that much more than can fail. Another perfect example is the Jetta, where one of the rear door latch modules was draining the battery overnight. The simple solution there was to unplug that door’s wiring harness and forget about it. I lose that door’s power lock and window, but the back doors will be coming off for the Ute conversion anyway, so who cares?

I understand that some electronics, like servos and pinch strips, are needed for doors and hatches to open and shut themselves. I have no problem with that. But it should still be possible to open and shut the hatch even if the electronics fail. This isn’t the case here. It’s impossible to open and shut the Flex’s rear hatch when the battery is dead or disconnected. Being able to get into your own car should never be a concern, yet here we are.

It also caused us two weeks of grief and stress, not to mention a fair amount of money on shop visits that ultimately didn’t solve the problem. We already know that it’s becoming more and more difficult to work on your own car, thanks to today’s sophisticated engine management systems and so on. Rather than fiddling with carburetor jets and manual timing advance, we buy a COBB Accessport and it does the work for us. You don’t have to pop the hood, get your hands dirty, or even have a clue what’s really going on in your engine to reap the benefits of a tune. But cars are now suffering from a problem that has plagued computer software for years – feature creep.

“Feature creep… is the ongoing expansion or addition of new features in a product, such as in computer software. These extra features go beyond the basic function of the product and can result in software bloat and over-complication rather than simple design.” – Wikipedia

As a writer of software documentation by day, I’ve seen this happen in many products I’ve documented. Programmers are geeks (to be fair, so am I), and sometimes they like adding new features just because they can. They don’t always stop to think whether the feature adds any useful functionality to the product. But it always adds more complexity, which means more that can go wrong.

Honda Civic wagon
Photo credit: Allison Feldhusen

Why do you need an entire computer to control a rear hatch?! Just give me a key operated lock on the outside – something the Flex doesn’t have – and a cable operated lever on the inside, like every other hatchback and wagon I’ve ever owned. That’s all you need, and problems like this will never happen. But no, Ford had to get all technical and complicated and dedicate an entire computer to the hatch – a computer that wasn’t functioning properly with the replacement hatch.

Now get off my lawn, you whippersnappers.

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