TPS / ECU drama continues…
The two+ hours drive home provided plenty of time to think about (read: obsess over) what had happened, why it happened, and what it meant for the future. It didn’t make sense—and yet it did?
- I thought the problem was Amazon TPS—but the problem came back with an OEM TPS.
- I thought the problem was the cable adjustment—but the problem came back after it was set.
Staring out into the abyss through the windshield, I found myself wondering if the OBD scanner dongle was to blame. I mean, let’s see now…
I re-installed the TPS and re-adjusted the cable. The logger read 60% or 90% no matter what. Just like it had done on four other TPS I had lying around. Mechanically, I was set. Electrically, something was off.
But I had already traced the harness between the TPS and ECU a couple weeks before and verified it was intact and secure.; at least at either end where things were most likely to be moved. I also confirmed the ECU was sending the proper voltage to the TPS. So I should have been set, electrically, too.
The only thing I did between the 4500rpm, 25mph drive to the office parking lot and the drive home was reconnect the scanner dongle to the OBD port under the dash. And here’s what THAT looked like…
- The logger was connected to my phone, but failed to connect to the ECU (for the first time ever).
- I disconnected from the dongle, closed the app, and then physically removed the dongle to reset it.
- The logger connected to the ECU first try, and then showed all systems nominal and ready.
- I drove around the block. Truck drove perfectly.
- I re-checked the logger. Now it was still logging, but ALL signals were frozen midstream. That is, the scales were still tracking time, but the signals were static/constant.
At that point, I was out of Ames and well on my way to Des Moines and the I-80 interchange. I closed the app and left the dongle installed because I wasn’t about to stop until I got home, let alone change something about the electrical system under these circumstances.
Was my ECU going bad? Did late-90s Mitsubishis have the same, leaky capacitor in the ECU issue as the early-90s Mitsubishis did? Was the no-name, $30 bluetooth dongle from Amazon—that had been connected and power-cycled almost daily for at least two years—acting up and somehow backfeeding noise through the OBD port?
Upon getting home, I pulled the dongle. The truck drove flawlessly for about a week. When the problem came back, it did so in the middle of an otherwise normal drive.
It was a rainy day. Fezzik had been outside in all of it. I took a dog to the groomer. As I was leaving the parking lot, I thought I felt the transmission slipping a bit, but I was getting on the highway so I crossed my fingers. 2 miles down the road, I exited the highway and it was clear things were about to get shitty again.
Over the course of maybe 5 miles, Fezzik went from driving perfectly fine to right back to being undriveable over 10mph. I roared the last two blocks home at 5000rpm at 20mph and he’s been in the garage ever since.
The kick panel was still off from when I traced the harness so I decided to pull the ECU and check for leaky caps. There were none. In fact, the ECU looked great, except for a stripe of rusty-brown surface corrosion across the back of the board. This corrosion cleaned up nicely, with minimal scrubbing with a new toothbrush and 99% isopropyl rubbing alcohol.
Removing the mud-crusted WeatherTech floormat in the process of getting in there, I discovered the carpet was wet (again). I pulled it back and found the insulation behind the rubber pad on the footwell was soaking wet. (Not seen, it was soaking wet all the way over to the center tunnel below the heater core, too, but did not smell at all like coolant. This was just water.) Was the windshield seal leaking? Had leaves or acorns or something gotten into my sunroof drains since I cleaned them in the fall? Where is the water coming from, and is it the cause of the fresh corrosion, and is that the cause of my struggles?
It’s looking like hanging the ECU over a sopping wet sponge for six months of winter might be taking a toll on the ECU. I’m hoping I can confirm the leaks, patch them, and get on with my life.
In the meantime, I’ve had the following items waiting on install, some of which going back to the fall of 2021:
- sound insulation for the walls and ceiling
- fiber optic, twinkle light headliner kit
- powered subwoofer (under seat)
- JL Audio 6x9 speakers
- seat heaters & switches for front row
- white/red LED reading lights for second row
- gently used door gaskets from an AZ junkyard
So, as much as I hate the thought of taking my truck apart to this extent without being abso-friggin-lutely sure it’s the right thing to do, it’s something I’ve been wanting to do for almost two years and this is probably the best time of year to do it (before it gets hot and humid in the garage).
I figure, IF the issue is caused by a damp environment—and I KNOW I’ve got water ingress issues—it certainly can’t hurt to address the water-inside-the-cabin issue. Fortunately, I have a lot of neat shit to install that should make this project relatively fun. (It’s been years since I’ve installed any actual mods myself.) If I do all this and the truck STILL acts up, then I think I can probably start ECU shopping. Hell. I might keep an eye out for a spare CA-spec ECU just in case.