Gremlins in the Subaru

Have you ever felt that the electrical and electronics gremlins are after your car? Have you ever wondered if there were a conspiracy at play? I did today.

For 18 months our dearest Subaru Outback did not have a working remote control. It did not bother much during the Summer but it was a painful experience during the Winter. We persisted. I took it to the dealer and even they said it is not worth the money we’d spend on it. So off I went, and mind you this was the most complex task I’ve tackled, trying to figure out what was going on.

The first obvious step was to change the cell. A single CR1620 off of Amazon. Didn’t work. Next I tried with a second remote and also changed the cell. Nothing. So that told me that, since the probability of two remotes and a single cell being bad is minuscule, it had to be in the car.

Enter the Gremlins

I then started off hunting the problem.

 First major set of checks:

I checked the usual and easy to check things like reprogramming the two remotes, and door jamb switches. No problems there either. That meant, tearing into the guts of the beast. This was a major head ache because it meant I needed to decipher the electrical circuits, port numbers, and colours. Things like this

I’d take a badly documented source code any given day over these diagrams that tend to span over multiple pages. I had to bite it, so I did. Poring over the diagrams, I was helped by my trust Multimeter. Served me well.

 Second major set of checks

The signal receiver unit; Subaru calls it Keyless Control Unit (KCU). Now I had no way of checking if the unit itself was healthy so I did the next best thing. Check the connections going in for continuity, for GND, and for voltage. That circuit was fine though I could not test the KCU itself. BTW this unit was tucked away under the passenger dash and the only way to reach it is to disassemble the whole bloody centre console. No way am I doing that. So instead I checked the terminals by disconnecting from the side and that saved me a ton of time both in tearing it apart and in putting it back together. I used a long nose plier with some electric tape on it to pull the connection. Something like this:


A closer look:

 Third major set of checks

The Body Control Module (BCM). This took me down the rabbit hole because I was presented with this

I didn’t see any splicing in the wiring diagrams. So is this nonsense? Anyway. I traced it all the way around to this

What could it possibly be? There’s nothing in the wiring diagrams and it is being held together by zip ties. For sure this is an aftermarket part. So I did the best and used Google Vision API. That didn’t help. Couldn’t read the text and the bloody thing had me hanging upside down and put strain on my lower back. I tried using putty model to get a negative and that helped a little with the text though it was still not very clear. So then I posted on Reddit. /u/mospo was the man who saved the day. It was an aftermarket alarm system. I wanted to rule that out too so I disconnected it. I then walked through the rest of the wiring diagram. Nothing.

So there I sat, dejected that all the diagnostics in the world did not fix the problem. There were two pieces I could not confirm yet – the BCM and the KCU. I had no way to confirm these but to go back to the dealer and get a Subaru testing unit and diagnostics tool. So there the car sat, half the guts opened up, nuts and bolts all over the place. Since my wifey needed the car, I ended up putting it all together, the problem not being solved.

We moved to Denver

In the meanwhile we moved to Denver and this diagnostic took the backseat. This was quite honestly the most difficult thing for me to solve. I had to walk through the circuits figure things out in the diagrams and all I had to show was everything was in spec. I even posted to Reddit, again.

 Micro Center visit

Now the main difference between Sioux Falls and Denver is that I can walk into an electronics store like Micro Center and pick up electronics. I can walk into Harbor Freight and pick up some tools. So there I was picking up a Raspberry Pi Zero and a Corsair mouse pad from Micro Center when I walked past an aisle with CR1620 cells on sale for $0.99. Not bad. Might as well pick two. Anyway, I came home and tossed the cells in the corner. They sat for a couple of days. I then decided, might as well give it a try. So I plopped one of the cells into my Fob… a drumroll and … nothing. It was a good try, me still clicking the unlock button on the fob. $0.99 x 2 is not too bad, me still clicking the unlock button on the fob. These gremlins have been bothering me, me still clicking the unlock button on the fob. I wonder where the nearest Subaru dealer would be, me clicking the panic button; literally and figuratively.

A thar she blows her alarm! I knew how Dr Frankenstein felt when the monster awakened because I heard the sweet sweet sound of a panic button setting off the car alarm. It was quite the therapy session. The rest of the buttons worked too. It just so happens that the unlock button doesn’t make a big of a sound so I wasn’t hearing it earlier.

So… what happened here?

It feels weird that the solution this this problem was a stupid button cell and while I am delighted that the remote works, I am left wondering what happened here. There are two potential answers I can think of:

  1. The CR1620 cell I bought on Amazon was dead on arrival. This is the most plausible explanation as I checked the old cell with a voltmeter and it recorded something like 2.6V when it should be closer to 3V.
  2. I worked on other mechanical fixes that involved the Indian Mjolinir aka a big hammer. I doubt this is the case because the electricals are generally well put together
  3. Jesus?


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