BMW Scanner 1.4 gotcha

N

nr.

Member
 The Fens
I did a quick search for this, but couldn't find any hits, so apologies if I'm re-posting known information. I recently picked up a BMW Scanner 1.4 from eBay [1], and the good news is that it definitely works. Installing the drivers on Win10 is trivial, and it reads codes and chassis information as expected.

However - be aware that the supplied cable isn't standard - certainly ground has no continuity end to end - I stopped checking here, but I suspect that the +5V supply is also open. I found out when I hooked up the scanner on the bench using another USB-A cable that I just had next to me at the time. This was a standard cable, and immediately, the laptop reported an excess power draw on the USB port. What's happening is that the unit is designed to draw power from the car (which it does) but there's nothing in the circuit to stop it trying to draw power from USB if it's available. This also means that when the unit is plugged into the car and laptop with a standard cable, it electrically connects your laptop to the car - which will almost certainly not end well.

This is a shame as the supplied cable is short and a bit wobbly - I'm going to dive into the circuit to disconnect the 5V rails from the USB socket so I can use any USB-A cable. If I remember I'll take photos and post it up here.

[1] https://www.ebay.co.uk/itm/154021453500
 
Hmmm, actually - there's something else going on... definitely the cable . But digging around inside the unit, I can't find anything connecting the power sides. That's all a bit odd. More investigation needed.
 
I’m no electrical expert but surely you need the cable to connect the car to the laptop in both directions so that you can both read codes and do coding?
 
enuff_zed said:
I’m no electrical expert but surely you need the cable to connect the car to the laptop in both directions so that you can both read codes and do coding?
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Absolutely. USB has cores in the cable for both power and data. Sometimes you don't need the data connections, say, for charging a phone. And you can buy charging cables, which only have the power lines connected. (You'll invariably pick one of these up when you want to transfer data from your phone to your PC and spend 20 minutes wondering why it's not working!)

In this case, however, I was thinking it's the other way around. The scanner is designed to take power from the car, and so only needs the data lines connecting to the computer. But there's something else going on - which I want to get to the bottom of! The only difference I can find between the cables is the outer sheath - which is not connected on the provided scanner cable, but is on my 'standard' cable. But as far as I can work out, this really shouldn't be doing anything other than providing shielding from interference.

(Oh, and worth mentioning, I'm no electronics expert either! Happy to dive in with a multimeter and oscilloscope, but really just a slightly over-enthusiastic amateur. I'm now approaching that point of a little knowledge being dangerous, so I'd probably best stop before I get to that point).
 
nr. said:
Absolutely. USB has cores in the cable for both power and data. Sometimes you don't need the data connections, say, for charging a phone. And you can buy charging cables, which only have the power lines connected. (You'll invariably pick one of these up when you want to transfer data from your phone to your PC and spend 20 minutes wondering why it's not working!)

In this case, however, I was thinking it's the other way around. The scanner is designed to take power from the car, and so only needs the data lines connecting to the computer. But there's something else going on - which I want to get to the bottom of! The only difference I can find between the cables is the outer sheath - which is not connected on the provided scanner cable, but is on my 'standard' cable. But as far as I can work out, this really shouldn't be doing anything other than providing shielding from interference.

(Oh, and worth mentioning, I'm no electronics expert either! Happy to dive in with a multimeter and oscilloscope, but really just a slightly over-enthusiastic amateur. I'm now approaching that point of a little knowledge being dangerous, so I'd probably best stop before I get to that point).
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Thank you.
I have a spare Scanner 1.4 cable and plug here so if you wanted to double check you could try that?
 
enuff_zed said:
Thank you.
I have a spare Scanner 1.4 cable and plug here so if you wanted to double check you could try that?
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That's an idea, thanks - I'm planning on popping up in the next couple of weeks to discuss airbags :) So I'll put my scanner and cables and multimeter in the car, and we can compare and contrast. I've bodged an easy solution for now - the wobbly bit of the cable was the A and that connects to the laptop - so I've just taped a USB extension to the scanner lead, so I now have a decent connector to plug into the laptop.
 
nr. said:
That's an idea, thanks - I'm planning on popping up in the next couple of weeks to discuss airbags :) So I'll put my scanner and cables and multimeter in the car, and we can compare and contrast. I've bodged an easy solution for now - the wobbly bit of the cable was the A and that connects to the laptop - so I've just taped a USB extension to the scanner lead, so I now have a decent connector to plug into the laptop.
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OK, look forward to meeting you.
 
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