Dongle trouble #4: solution. Sort of

Short glossary: We have no ties with KONNWEI. Actually KONNWEI902s are knock offs of real ELM327 based hardware, but they have been the only consistently stable ones we have found. And we haven’t spotted “knockoffs of KONNWEI knockoffs”. Yet.

It seems the manufacturer has cost-optimized the hardware, which is not bad at all. However, as said in the previous post, there is a problem with one component. Recent deliveries have not worked and actually I heard of a few drivers getting weird error messages in the dash. Not fun.

Long story short: we would gladly recommend something that works, but we have no decent alternative. The solution at this moment unfortunately is tinkering. It’s not hard to do and you don’t need fancy knowledge or tools. Just a fitting hex tool and a sharp exacto style knife. I did this on a non working dongle and can confirm it works.

  • remove the 4 screws
  • gently pry open the case. Be careful that the connector and the front stay in the half that has the main PCB mounted on
  • check this post to determine if you have the old or the new design. Unfortunately there is no way to check this from the outside *)
  • if the design is “old”, stop here. If your dongle does not work there is another problem
  • if the design is new, locate the chip with 8 pins roughly in the middle of the PCB
  • just above and between the 2nd and 3rd pin of that chip, there is a tiny black component (resistor), see picture below
  • carefully cut away the middle part of the resistor. Ensure you do not damage the track going up on the right side. Damaging the track on the left, going to the second pin is not a big deal. Of course if you have soldering skill, you can also de-solder the resistor.
  • close the case and put the bolts back in. Note that one side has hex formed holes, these are for the nuts.


I drove with a modified dongle today without any problems. The only issue I had were more than usual ATMA timeouts and I had the impression it was all a bit slower than what I am used to. The former I need to investigate a bit further, it can probably be fixed with a modification in CanZE, the latter might be subjective, or maybe the processor is a bit slower in the optimized design.

We fully expect KONNWEI to fix the problem in the long run, and it seems there are already new designs shipped with the new resistor. part of current stock seems to be troublesome though.

*) If you have a multimeter there is actually an external way to check the dongle. Measure the resistance between pin 6 and 14. If it’s 20 ohms, you have a bad dongle. If it’s 120 ohms, it’s fine. BTW pin counting is from right (1) to left (8), top row, meaning in the wider part of the connector first, then the bottom row, again right (9) to left (16) in the smaller part.

EDIT: The leafspy guys reported on this last April. Oops! Oh well! More pictures there too BTW.

Posted in Hardware
One comment on “Dongle trouble #4: solution. Sort of
  1. MartijnEV says:

    Haha that’s much easier than first opening the case 🙂
    “Thou who does not own a multimeter shalt not try to do this at home” 😀

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