INPA K+DCAN UBatt and Ignition black solution

Here is the customer solution to the BMW INPA K+DCAN USB cableĀ UBatt and Ignition black always black issue.

So, got my self a high quality INPA K+DCAN Interface from China.
Interface looks very well designed and has a nice PCB, all components soldered properly on the board.

Installed BMW Standard Tools 2.12 as per instructions of our friend Bimmer with all software he provided in his thread.

While connecting and testing the interface I found the UBatt and Ignition dots were always black. Interface connected to OBD2 or not.

Decided to try to fix this and started to read.
Found that RI from TTL-USB converter is used to indicate UBatt and DSR/DTR is used to indicate Ignition ON.

Traced back the tracks from OBD2 pin 1 and found 2 resistors mounted on the board as voltage dividers. However the values and connections were as:
Pin 1 -> 1K -> 47K -> GND.

These were not the proper values to get ~5V at the junction between both resistors. Changed them to 47K and 22K. That solved the Ignition ON indication problem. See picture “Ignition.jpg” resistors R5 & R6.

Then moved on to the UBatt problem.
Seems the RI pin on the FTD232RL is directly connected to GND on the board. That is why the UBatt dot is always black.

So, I lifted the pin (UBatt_1.jpg) and used a transistor BC547/1K/10K as inverter to pull this pin to GND if the interface gets +12V on pin 16 of the OBD2 connector (UBatt_2.jpg).

Now both indications work as intended.


inpa-k-dcan-repair inpa-k-dcan-UBatt_2

You can easily find out if it is the K+DCAN interface or soft setup the reason for the black dots.

Just start Inpa software without the interface connected to the OBD2 in the car or the USB. Dots should not be black. Must say that I have not found any entry yet in Ediabas.ini which will cause the dots to be black without an interface connected. There are entries to instruct EDIABAS to flag an error or not if the Ubatt/Ignition are not sensed by the soft.

I expect the software requires the info that power and ignition is on, hence the option to have the error detection ON or OFF in Ediabas.ini.

I’m not an expert in BMW, but for Mercedes the software instructs to switch ignition OFF at a certain moment, detects that and starts a timer. After the timer expires the instruction is given to switch Ignition ON, detects that and the program continues. Expect BMW soft has similar functions like that. May be some one more experienced in BMW diagnose can shed some light on this.

Please find my handmade sketch for the circuit attached.
Blue: existing components on board
Red: new components to be added
Green: wires to be soldered

Transistor can be any low power NPN type.

I expect that the circuit also will work without the transistor, but then the RI pin must be inverted in the FT chip configuration with Mprog and the junction of both resistors connected to the RI pin. How ever, I did not test this yet.inpa-k-dcan-UBatt_3

The modification is not required to communicate with the car. I did diagnose an E46 succesfully before these mods.
If yours does not communicate with your car then check:
– if you have 20pin connector at engine bay. If so, you should use that one for diag and not the OBD2.
– If you can get data from engine ECU but not from other controller then you should bridge pin 7&8 in the interface.
– if ediabas.ini is set to std:obd
– if the right port is set in ediabas.ini (expect this is correct)
– if port latency is set to 1 in system hardware

If all is set ok and you are at the right diag connection at your car then download Free Serial Port Monitor to see what is going on between PC-interface-Car. You can actually see the requests and replies.
This free software also shows you the status of the RI and DTS/CTS signals, very handy while testing with the resistors and transistor.