2000 D2 V8. Crank, but no start P1842 and P1843 codes
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Drifting
Joined: Sep 2025
Posts: 34
Likes: 9
From: El Paso, TX
I swapped to the other BCU and it starts runs and drives. Now to deal with the 3 amigos and the stuck on brake light and the exhaust bolts that I snapped while changing the CKP sensor. Thank you to everyone who offered suggestions and help!
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Drifting
Joined: Sep 2025
Posts: 34
Likes: 9
From: El Paso, TX
@Kurgan swap the crank position sensor first if you haven't already, but what finally worked for me was swapping the ECU and possibly the BCU as well. I got the original and new BCUs mixed up when swapping everything out, one worked and the other didn't. I'm fairly certain the new one worked because I no longer can use my key fob. Either way if you have to swap the ECU and BCU get a matching set to be safe
Overlanding
Joined: Jul 2024
Posts: 24
Likes: 3
From: Aberdeenshire, UK
@Kurgan swap the crank position sensor first if you haven't already, but what finally worked for me was swapping the ECU and possibly the BCU as well. I got the original and new BCUs mixed up when swapping everything out, one worked and the other didn't. I'm fairly certain the new one worked because I no longer can use my key fob. Either way if you have to swap the ECU and BCU get a matching set to be safe
I have a matching set ECU & BCU from the same donor vehicle. Does that cure the problem?
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Drifting
Joined: Sep 2025
Posts: 34
Likes: 9
From: El Paso, TX
It fixed mine can't say for sure it'll fix your issue, but it's easy to swap and test out since you've already got them
Rock Crawling
Joined: Nov 2023
Posts: 289
Likes: 104
From: Colorado and New Hampshire
To me the round dome solder looks like a repair. From what I have seen, the tent-like solders (pole in the middle with solder drooping outward) are what can be a problem. On the tents, the solder is thin enough that high current heats the solder, eventually melting it away in a dark black circle around the pole. A magnifying glass is useful to find the faulty solder joints, since they can be hard to see with eyeballs alone. The repairs I have done re-melt the solder and add more, that can create a shiny dome shape. More solder makes less resistance that gets less heat when current flows.
What @JohnZo says about it being hard to identify a bad solder joint by eye is true. If one has any reason to suspect a bad solder joint on a board, it is a decent idea to retouch all of the joints. What John says about adding solder and ending up with a dome is something I'll respectfully call a bad idea though. Excess solder runs through the hole to the other side and you end up with excess on both sides. Depending on what the device is that's attached there, you could be causing an invisible short on the topside of the board, plus, it's just too much solder. Goldilocks joints - not too much solder, not too little solder, just the right amount of solder.
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