Build thread

[speedjunkie]

I got a message back saying the gauge is toast. So now I'm back to trying to decide which of the expensive options makes the most sense. Ugh.

I still have not heard from anyone I've reached out to either about doing digital gauges.

[speedjunkie]

After some more thought, I've decided to just get all new Speedhut gauges. While I'd love a digital setup, the one being developed now is probably still a few years from completion, and I don't know how to build it myself, nor do I have the time.

I was considering just replacing the two gauges, but since this version is no longer made and they have made lighting advancements, they wouldn't look the same. The problem now is their new GPS speedo doesn't have a cruise control output. I had also considered getting dual, triple, or quadruple gauges so I could fit as much info as possible, but the pressure gauges don't read high enough, and possibly some other gauges too. And I never really found a combo I liked. Also, they don't do cruise control on those either, and I like the classic look of just a regular analog gauge instead of looking busy.

However, their programmable speedo has a cruise control output. We're back in the game! The only problem with that is I have to determine which of two wires at the back of the gauge cluster I need to run the speed sensor to. Well, that's one of the problems. When I built the harness for the Haltech, I ran the speed sensor directly to the ECU, so I have to rewire that first. It's supposed to go to the cluster first, then to the ECU and cruise control module, but the Speedhut speedo outputs a 4k square wave signal instead of 4.1k, so I don't want to take any chances on that causing further issues and I'll probably just branch off from the ECU wiring and run to the cluster too.

Now I need to decide which extra gauges I want, and it's looking like it will be water temp and oil temp. Those are the ones that read slow through OBDII anyway. The pressure gauges read fine through OBDII, and the Speedhut oil pressure gauge doesn't read high enough. So Tach, speedo, water temp, oil temp, fuel level, and boost. It'll be about $1330. Ugh.


In other news, I made a bracket to mount the fused power strip in the same place as the old one, and it came out pretty nice. I also measured the depth of the oil pan and I think the Turblown pan won't hang below the subframe, so I'll probably be swapping that too.

[speedjunkie]

Today I tapped a wire into the gray/brown wire coming from the speed sensor on the transmission and sent it to X-14 which eventually ends up at 3C behind the cluster. I'll need it either way, whether I do the Speedhut gauge or a digital display.

Speaking of which, Jason Kaiser seems interested in making some digital displays. He's been looking for round displays anyway, I assume for the same reason. We're still not sure what exactly will be needed to make them work, he's looking into it more. So the gauges are on hold for now.

I also found a display from Ghostdashboard that might work, but I'd need to hack up my gauge cluster face and fiberglass it, and I'm not too keen on that. It would be fairly plug and play it seems, being that it will take CAN from the Haltech and I can wire in any extra things. Another drawback is they're in Brazil, so there would be a language barrier.
https://ghostdashboard.com/

I also starting wondering if there is an OEM dash that could be worked. It would need to be hacked/broken or whatever so I could make changes, but I'd love to have something that has a curve to it so it fits the FD dash better. I was looking at one from an Audi, 2018 or newer.

[speedjunkie]

Well my mind started wandering again haha.

I started talking to OneGauge because they have a hub that will take a CAN input from the ECU, or it will take OBDII, but CAN is way faster. You can also connect other sensors, relays, and things like fuel level, blinkers, etc. So that solves all my issues getting info to a digital dash. I was talking with them about multiple round displays and he started looking into it, and found some things that will work together. So it looks like I might actually have a digital display before too long. Depending on how long it takes him to research and test everything. But it's a huge help so I can't complain, and he's VERY helpful. https://www.theonegauge.com/product/one ... t-builder/

Then I got to thinking, as much as I've always loved the original gauge cluster with the separate gauges, I'm not sure how much info I could really fit on them, as opposed to doing one big display. However, I've never been a big fan of single displays, they just never look like they belong in the rounded gauge hood because most of them are rectangular, or the ones that aren't rectangular just aren't big enough and there is so much wasted space. Along with that, I've never been a fan of having the brand name on the display, and they're not very customizable.

I've seen some of the Audi Virtual Cockpit clusters and with the curvature at the top, they seem like they would match pretty well with the stock gauge hood. I found whole clusters on eBay, but I've also found just the screen itself, and the measurement looks like it might just work. It covers basically the entire area where the original gauge holes are, almost perfectly to the far edges of the fuel level and speedo, and up just past the blinkers, but the top corners are angled so it would clear the curvature of the hood. OneGauge said they'd hacked OEM clusters before and that I could buy one and send it to them to try out.

I was thinking about just getting the screen, but the inner part of the Audi cluster would be good to use to give it some depth and a clean mount to the stock face. OneGauge told me I'd need the whole cluster, but it's pretty thick and I don't think it would fit, but maybe trimmed down, or if I can do just the display and the front piece, I think that would fit.

[speedjunkie]

The project has shifted a bit. Once I got the Audi cluster and took it apart, I set the display where it would go and it fits perfectly. However, due to the seemingly proprietary ribbon cables used, it would be much easier to just get a 12" display. I turned the Audi screen upside down to see if another display the same size would fit. There are a few different options out there that are about the same size, but rectangular in shape instead of the top corners cut off like the Audi display. It does fit, but just barely. But since it fits, and those displays would be much easier to wire into, I decided to use one of those and just use the Audi inner ring of the cluster to frame it.

You can get a display from OneGauge or PiDash with their Raspberry Pi 5, but it's about $700 and I found a display from China that has a frame that isn't so big and allows more of the screen to show, so it will be easier to get the cluster frame exactly where I want it. Also, it's about $150 shipped. The Pi from those places is also about $250 to $275, depending on which one you buy from. You can buy a Pi 5 with the same RAM from Mouser for $60, but you still have to install the software for the Pi and for TunerStudio. Both of those cost money, but still not as much as they're asking.

The biggest issue is boot up speed. OneGauge said the boot time is about 20 seconds, and I'd like to get it much lower than that. If I could get it sub 10 seconds, that would be good, closer to 5 would be even better. But to get it that low, you really have to strip down the software. I've read quite a bit about how to get it faster, but since I've never done any of this before, I'm not really sure how to do what is being described, and what all is possible. I've read things about using Buildroot, running a kernel, whatever all that means lol. I've also been looking at DietPi, which is a stripped down software, but even that still boots at around 15 seconds unless you do a lot of work. It seems like most of it is disabling or delaying the display from finding Wifi during boot up, things like that.

I was considering using the stock speedo to handle cruise control, but that goes through a ribbon cable and would be too much of a pain to set up, and the board is rather large to just be hanging out on the back of the display. So I bought a Dakota Digital converter to run cruise control. And I bought two power converters to change 12V to 5V for the Pi 5 and HDMI to LVDS adapter board. I bought the OneGauge hub and the display from China, I'm hoping they'll both get here in the next week or so. I'm seriously thinking about buying a Pi 5 and trying different software to see if I can get the boot time down.

I'm getting antsy about getting this project done, so I've been doing other little things on the car. Pulling out all the wiring for the Speedhut gauges, installing the fuse block, etc. I added a wire for cruise control to work, and I pulled the fuel level wiring all out and reconnected the stock wiring. I believe it's mostly ready now, aside from adding more wires for all the indicators and things I need to wire into the hub. I plan to mount all the boards and everything to the back of the display.

[speedjunkie]

I bought an 8gb Pi 5 and an active cooler for it and got those today. Part of the reason I got those was to experiment and see if I could get it to boot faster than 15 or 20 seconds, to see if I can get it sub 10 seconds.

I also finished all the wiring for the warning lights. That was a task because I had to figure out which ones would be voltage based vs ground based so Mike can assign them correctly in the hub, and I'm still not completely sure on some of them but I'm about 95% sure. I also got the resistance readings again for the fuel level sender, 93ohms empty and 15ohms full, but I'm asking to have them set at 80ohms empty and maybe 20ohms full. Cruise control and the seatbelt indicator I still haven't figured out, but I think it's just because the car isn't running or at a speed where the cruise control can be set, which I think is above 20mph. Well, that and I just realized it won't work anyway without the Dakota Digital box plugged in. Wow, what a bonehead mistake.

I've also decided to run the two indicators for water injection (the solenoid relay and the pump driver) to the display as well, so I don't have to worry about where to mount those two little lights.

I still haven't heard anything from good-display where I bought the display. I sent them a message though. If I can't get that display, I might just get the display and Pi from OG as well.

[speedjunkie]

The guy from Good Display reached out and said they just wanted to test the display first to ensure it's working properly before shipping it overseas, and it should be getting here Thursday.

I had an incorrect wire tapped for the high beam indicator, using the ground wire instead of power, so I fixed that. And I ran the two water injection indicator wires to where the gauges sit.

I had an issue trying to start the car, I kept blowing the 40a B2 fuse in the engine bay. I thought maybe one of the gauge wires was touching metal, but it only happened when I turned the key to start the car. When I was pulling the gauge wiring out of the engine bay, the 10ga wire I ran from the ignition switch directly to the starter was tangled up and got pulled off the starter and was grounding out on the engine block, so I fixed that too and started the car so I could test the seatbelt wire (still didn't work) and cruise control, again forgetting that it won't work anyway without the Dakota Digital box hooked up.

I was trying to figure out what I was going to do about the gauge hood. I bought a file from Drakes that's basically a blank, and I'm going to scan my Audi cluster and have someone mesh the two together and print it. Then I just have to figure out how to mount the display to it, which might end up being the easiest part of this project. I'm excited to get this wrapped up, but there's still a long way to go.

[speedjunkie]

I'm leaning towards not using the Audi screen. I haven't found any driver boards for the 64 and 13 pin ribbons on it, and I'm not sure what resolution it is, so using just the screen seems like a lot of work, if it's possible at all. I bought a pigtail with connectors from eBay so I could at least power on the gauge cluster. I was concerned about getting fuel level and coolant temp onto the screen, as those go to the two gauges on either side, but Matt Heimerl saw it today and said the largest connector brings CAN from the ECU, so that would make that much easier. Huge win! Brett Currier printed out the wiring diagram from AllData and brought it by. I was thinking the black connector with two wires was the power and ground. He told me that is fiber optic. Huge loss! lol This pigtail was cut out of a harness, so I know the fiber would have to be repaired/reterminated, but I'm not sure what I would send it to anyway lol. So using this display is looking more unlikely.
20250314_163710 by Eric Jausel, on Flickr

The screen from Good Display seems like it would work really well. It's slightly smaller than the Audi screen but still has the corners of course, and fits the gauge hood really well. The bezel is really small on all sides, and the screen is just barely wide enough for the Audi frame. Hopefully the active area is wide enough to cover all the way to the edges.
20250313_165729 by Eric Jausel, on Flickr
20250313_165723 by Eric Jausel, on Flickr
20250313_165816 by Eric Jausel, on Flickr
20250313_170400 by Eric Jausel, on Flickr
20250313_170329 by Eric Jausel, on Flickr

The problem is I didn't know that you have to find a driver board that has the same resolution as the screen, and this one is 1920x720. I didn't find anything for a bit, but I eventually found a couple on AliExpress that would work. I was looking for boards that had micro HDMI and USB-C inputs, along with a 50pin TTL interface for the screen (even though their data sheet says it's LVDS, but I can't find anything LVDS that's 50 pins, only 40 and below), and finding something that has all that and the proper resolution is apparently impossible, so I got what I could. These boards have regular HDMI and a 12V 2A input jack similar to on a laptop (5.5mm x 2.1-2.5mm). The ones that aren't for touch screen have a little switch board included. I bought a board for that, and I bought another board and screen that has touch screen. One of the reasons for touch screen is because there aren't dimming options for these displays when it gets dark, so Mike at OneGauge said what they normally do is have another gauge design that is darker and they use the touch screen to just swipe to the darker layout. The non-touchscreen board has a way to dim the screen, but if there isn't a way to wire it to the lighting wiring so that it dims automatically when I turn on the headlights, I'm not sure how I'd do it because the switchboard will likely be behind the dash, unless I can find a subtle place to put it. And I'm not even sure whether that switch is on the switchboard or the driver board.

I chose the touchscreen option on this link.
https://www.aliexpress.us/item/32568015 ... ry_from%3A

This is the board I bought. You have to click on the option that shows just the board. The board itself seems to be exactly the same as the other one, but the cabling is a bit different since the other is touchscreen.
https://www.aliexpress.us/item/32568063 ... ry_from%3A

I also bought this board because I believe it will work, but we'll see. It's not a huge risk at $22.
https://www.aliexpress.us/item/32568061 ... pt=glo2usa

The other things I've bought for this project recently is a 64GB micro SD card with 200mb write speed, which is the fastest I could find, and an HDMI to micro HDMI cable (to go from the Pi to the driver board). I have to download TunerStudio, which is $70 IIRC.

I had reached out to AI One Designs and Shane Drake about making the gauge hood, neither were interested. The CAD that Shane sent me has no gauge holes cut out, no warning light openings, but also doesn't have the cigarette lighter hole. While the cigarette lighter doesn't fit aesthetically with a digital gauge, I still use it occasionally for power. He's working on one with the cigarette lighter opening for me anyway. I still have to call some local places about meshing and printing this.

Then I have to figure out how to mount the display to the gauge hood, which should be fairly easy, hopefully lol. I need something easy with this project, at least one thing lol. The Good Display screen doesn't have a way to mount it, so I figured I'd make a frame for it and just tack mounts to it for the stock mounts. The touchscreen display does have some mounting tabs on the back, so that might be easier. My plan has been to mount all the boards to the back of the display, but there might not be enough room. Also, I could minimize install and removal difficulty if I keep the OneGauge hub, DD box, power converters, and Pi on the dash and mount just the driver board on the display, that way I would only have to disconnect power and HDMI to remove the cluster. Although I'm not sure if there is enough room for all those things on the dash either. It might be easier to mount them to the display.

[speedjunkie]

I got the AliExpress items about a week and a half to two weeks after ordering. When I first connected them, the screens didn't show anything. OneGauge said they typically need HDMI input to turn on, and that is true for these as well. It's pretty bright at 1000nits. Both screens are. There is an option screen on the card I guess, because the card works on both screens and the same options come up. Luckily you can adjust screen brightness without going into the options, just by pressing the up and down buttons, but I'd prefer having it adjust automatically with the headlight switch or an ambient light sensor. More on that later. I was told I can change the aspect ratio on the Pi, so I can fill the whole screen. I'm also wondering if I'll be able to get this screen to turn on automatically when turning the key or if I'll have to use the switchboard. I really don't want to have to use that board at all.

One of the two same cards I got is already bad, I'm not sure if I did it or it was like that. One of the (what looks to be) power wires came out of the TTL end, and it's so small I'm not sure I can fix it so I'll order a replacement. The third card that was different doesn't look like it will work, but I'm really not sure.

I haven't connected the touchscreen portion of the other screen yet because it's powered by USB and I don't have the Pi going yet. But it's a bit bigger than the screen I'm planning to use, and I think it's the same screen that PiDashes sells.

I bought a 110v to 12v power converter today so I can do all this work at a table instead of in the driver's seat.

Back to the topic of dimming. I found an ambient light sensor that I thought would work, but supposedly it's not possible to dim a screen through HDMI, so it wouldn't matter what kind of dimming option I'd try. I also looked into using a relay triggered by the headlight switch, but I don't see how that would work either. I'd really love to get this to work though. Either option uses a few of the GPIO on the Pi.
https://www.uugear.com/product/uugear-l ... og-output/

I'm now looking at using an NVMe SSD instead of a micro SD card. I'm just looking for a way to get boot up speed as fast as possible, although this has more to do with getting TunerStudio running, and boot up speed is more dependent on running as little as possible on the OS. I'm also looking at SSD because I saw a video from a guy overseas that had two of the exact same SD cards I'm planning to use and both failed within a couple months lol. OneGauge told me that the SSD doesn't boot up much faster than the SD card, and that a battery backup prolongs the life of an SD card, so that might not be an issue for me anyway. Another thing about using this SSD is that the GPIO pins would be unusable, so dimming wouldn't be an option even if one would work.
https://www.mouser.com/ProductDetail/Ra ... Zz0A%3D%3D

I started thinking about using an Arduino or ESP32 instead, but I guess they won't run an HDMI screen and there are no options I could use that are bigger than about 10" and I need the 12.3" to fill the cluster more.

I'm having a very hard time finding a place that can print large files, or just a place that will get back to me in general. I've only talked to one company so far and their printers were too small.

OneGauge said my hub is ready to ship, so I should be getting that soon.

[speedjunkie]

20250413_210547 by Eric Jausel, on Flickr
I've made some more progress, although I'm still stuck on a couple final things. This is how the Raspberry Pi will be mounted, and the two power supplies (for the Pi and the UPS) on the right. The little board has the ambient light sensor. I don't know if that will work yet, but if it does, I think I'm going to mount it under the center speaker grille on the dash, or have someone print another grill with a hole just big enough for the sensor, that way it's inconspicuous. I was thinking about mounting it where I have the rear camera for the dashcam, where the rear window sprayer used to be. I want to print a cover for that camera anyway, and that way it would truly get an accurate amount of light, but I don't believe it is weatherproof lol.

I posted in a Raspberry Pi group about this project and a guy in NY offered to help. He helped me for a couple hours each day for three days, and we got an image written the second day but it wasn't quite right. We went back to add more for a new image but he hasn't been able to help since. We're building a root file and it's supposed to boot straight into Tunerstudio as the desktop. It doesn't do that currently though, and there are a couple other small issues I believe. It does boot into the terminal really fast though, within a few seconds, and that's on the SD card which writes 200mb/s. The SSD writes about 3500mb/s, and the current image is about 2500mb, so I hope my math is correct to get me thinking it will boot pretty much instantly. I think I'll need to add some way for the UPS to shut down after a certain amount of time keeping the Pi on so it can do a soft shutdown. I need to see if a dimmer will work, and if it doesn't boot instantly or near instantly, I'm going to set up a splash screen with the Mazda logo or something. I think there are one or two other things I need to implement in there too but I can't remember right now.

I still haven't found a place to print the gauge hood, but I think I'll work this piecemeal and try to scan the Audi piece myself, then see if someone can mesh the files, and from there I'll send that file to a few different big companies and see who can do it. There has to be someone out there that can. If not, I guess I'll be cutting my stock hood and doing some heavy fiberglassing and filler work. At least then I'd know for sure it would fit perfectly to the dash.

20250413_165616 by Eric Jausel, on Flickr
This is how it will all be mounted behind the cluster. I was going to mount everything to the cluster itself and run all the wires through a connector, but I figured that's more weight on the cluster that doesn't really need to be there, and this way I'll only need to disconnect the power and HDMI cable for the display itself, that's a super easy disconnect. Well, those and the headlight switch and cruise control switch. I was going to mount the OneGauge hub flat on that plastic piece where the Pi is sitting, but it's larger than I expected it to be (that's what she said). I was thinking it was going to be the newer version which is 5" long, but this one is 7". The good thing is it fits pretty well perfectly to the stock plastic, the vertical pieces of the dash are spread apart just enough to mount it there. Also, since the hub is 2" tall but 3" wide, it leaves a little more space/depth for the display by mounting it this way. The Dakota Digital SGI-100BT is mounted lower, mainly because I ran out of room for it, but it fits perfectly there. The only reason I have that is to retain cruise control. I rarely use it, but I definitely want to keep it. I ended up deciding to run those wires under the plastic to keep them out of the way. I've decided to try to use rivnuts in the plastic to make install and disassembly easier. Not sure how well it will work, but I used nuts and bolts on the DD piece and it was kind of a pain in the ass, so if I ever remove that, I'll probably try to install rivnuts there too. I'm awaiting some heat shrink for the CAN wires, then I'll run those through the hole to the upper right of the OneGauge hub to keep it off the Pi, so any excess heat from that shouldn't be a concern. The CAN board is just to the left of that hole. Once OneGauge gets back to me about where each wire needs to go on the hub, I'll finish all that wiring and it will be much cleaner. I'll post another pic once it's all finished. This hub has GPS that I'll use for the speedo and any other thing GPS related, and an accelerometer so I can see if any suspension improvements net a better skidpad result, which should make the additional $50 fee worth it for the possibly one time I ever use it, if even once LOL.

And the day after my last post, I disconnected the switchboard and the screen turns on and off with turning the key on and off, so as long as I can get the screen to dim, I'll leave that board disconnected.

[speedjunkie]

I finally used my scanner and got one decent scan of the Audi cluster. I tried several more times after that to get a better scan and they were all shit. I tried so many different things with no luck. I have no idea what I did the first time to get a fairly good scan, but I couldn't repeat it. I'm going to try a few more times with different techniques, but this might be the only one I can possibly use. I only need the inner part of this, so I think there is enough here to work with. It obviously needs to be cleaned up, and some things cut away and parts of it adjusted. I had heard before that this scanner doesn't pick up dark colors very well, so I taped off the parts I didn't want to scan and sprayed the rest with white plasti-dip. That was a waste of time because it had no problem at all scanning the entire thing, and the black background that I used lol.
20250418_171623 by Eric Jausel, on Flickr

I downloaded the TS Dash image and tried it. The site says it won't work with Pi 5 yet, but someone on 7club said they knew of others with a Pi 5 that got it to work. It didn't work for me though, so I downloaded DietPi and installed that. That was still a huge PITA, for someone that has never dealt with Linux. I finally got it all installed and got a few other software programs I needed that were preloaded on the Pi I guess, but now I'm having an issue even getting TS to start. I'm having a hard time figuring out which commands I need to put into Terminal to get it started. I found a page with instructions, but some of them are a bit different than what I've gotten to work so far, so I assume the rest of the instructions are more of a suggestion as well. EFIAnalytics is working on a TS Dash image for the Pi 5, so I'll probably try it when it's released, unless DietPi with LXDE desktop is fast enough already.
20250419_182022 by Eric Jausel, on Flickr

I need to add some kind of fan control, because the fan isn't even kicking on. I think I'm going to add a small fan to blow air across the whole Pi assembly though, that will come on with 12V ignition. I need to set it to where the Pi starts powering down when I turn the key off, and the UPS should shut down after the Pi is powered down. Supposedly it's smart like that lol. I need to try the screen dimming stuff, but I already know what I need to put into Terminal for that, hopefully it works lol. And I need to get TS to autostart, once I get it to work at all.

[speedjunkie]

I recently discovered a problem while boosting hard, the car just falls on its face. I sent a log to Joe and he said the wideband and crank trigger are dropping out under load.

While checking grounds, I discovered that the sensor grounds and battery grounds had continuity together. I finally tracked it down to the knock sensor. Apparently I've had the sensor ground wire running to the side of the sensor that is grounded to the engine block. So I'll swap those tomorrow.

I've also noticed that my CAS wiring is a bit jumbled, or so it seems. It looks as though it's wired for a VR setup but I have hall effect. I still need to look into that more though.

[speedjunkie]

I traced the cause of the grounding issue to the knock sensor, I just kept checking for continuity as I unplugged connectors until I found it. It grounds to the block (through one of the terminals), which is grounded to the chassis, then the battery. To the knock sensor I have a signal wire and the sensor ground wire, and guess which one is attached to the terminal that's grounded to the block. I thought maybe the sensor was bad initially, but realized it's a feature, not a bug. I contacted Chris Ludwig and he told me to swap them out for a newer version, Bosch 0261231188. I bought a couple of those from Amazon. He said they don't ground to the block and that it won't matter which way they're wired, but I looked up some pics and they look like they ground to the block, so what I'll probably try to do is just use the signal wire and let the sensor ground itself.

I found an old pic of the CAS wiring and it's correct, and I also ohmed out each wire to verify that it's good.

There's a guy in England doing the CAD work on the interior pieces and he was working on it today. I also sent the files to Schmidt Proto in Minneapolis, but I haven't heard back from them again yet to see if they'll actually do the work. They have printers big enough to print it though, so hopefully I can at least have them do that part. There's another guy on 7club that offered to print it, but his printer is a tad too small, unless maybe printing at an angle.

[speedjunkie]

I got the new knock sensors the next day and installed one of them after verifying that it doesn't ground to the block. I started reconnecting all the connectors, installing the UIM and all that. But before I finished, I verified again that the grounding issue was gone. Nope, it was still there lol. I disconnected the knock sensor and all the other connectors again, still there. The next day I discovered that it was the CAN cable to the OBDII device I'm using, but it was actually the device itself creating the ground issue. I reached out to OBDLink and this was their reply.

"The behavior you're observing — continuity between sensor ground and battery ground when the OBDLink EX is connected — can be normal, as the EX connects to the vehicle’s diagnostic bus, which typically shares a common ground reference with both systems. Many vehicles internally tie sensor and chassis grounds together at some point in the electrical system, and the EX itself doesn’t actively isolate these grounds.

That said, considering your past electrical incident involving battery over-voltage and damage to other electronics, there’s a possibility the EX may have been affected. While the EX is designed with internal protection, a severe over-voltage event can exceed those protections and potentially cause unexpected behavior.

To determine if your OBDLink EX is still functioning properly:

Try using it in another vehicle, if available, to verify normal operation.

Check for any irregularities in communication or data retrieval using the OBDLink app or a third-party app.

If you notice any abnormal heat, error codes, or failures to connect, it could indicate internal damage.

If you'd like, we can help evaluate the unit further or assist with warranty/replacement options depending on its purchase date and condition. Let us know how you'd like to proceed."

Considering continuity between the grounds goes away when I disconnect the OBDLink, I doubt the ECU acts as he's saying, but it's also not clear whether it's bad or not since it doesn't actively isolate the grounds, but I also had the electrical issues that destroyed the gauge.

I did swap back to an AGM battery last night, it's a Duracell CYL10009, which is the same size as the ATX-30. It has 400CCA, which is a little more than half the ATX-30, and it's 22lbs instead of 5lbs, but at least it's not lithium. I also removed the alternator diode cable just in case. I'm driving the car up to Aurora tonight to stay with my buddy and then we're going to Josh's shop so Joe and I can work on the car and look into this issue on Saturday.

[speedjunkie]

I took the car up to Joe at Josh's shop yesterday. He said after his first drive that it was happening in every gear, not just 2nd. We tried several different things with no luck. We verified wiring again, and voltage and ground. We swapped his HE sensor from his car to mine, and at first it looked better, but the next run it was back to what it's been doing. We swapped his sensor standoffs onto mine because they're a bit shorter, no luck. We added different thickness washers to the standoffs, no luck. He made some other changes in the calibration but those didn't work either.

We thought it might have been the TPS, but he checked that and the wiring and all that was good too. One of the trips out it threw an error code again for trigger reference error. On the way home I noticed that the wideband read in the 6s when I was pulling away from a light, and looking back at some logs today, it showed in the 9s as it dropped out and the car shut off, so I'm going to replace the wideband sensor and hope it fixes it. We're lost at this point.