Inside a fake ELM 327

I got myself on of those cheap Bluetooth OBDII dongles but it didn’t work in my car (2005 Dodge), it simply couldn’t detect the protocol which is SAE J1850 VPW used on most Chrysler/Dodge I believe before 2008. So I took it apart and as you can see in the picture it has two stacked circuit boards the one of top has a bluetooth chip (BEKEN BK3231Q) and a CAN protocol transceiver from NXP (TJA1040)

Fake ELM327

The flip side of the top board contains a CAN controller (MCP2515) from Microchip.

CAM controller MCP2515

However, and what is surprising is the bottom board which contains only voltage regulators for 5v and 3.3v and most of the OBD-II pins are not even connected!
OBD-II connections

Let’s compare  the connected pins to the pinout of the OBD-II connector in the image below


So the 12v VCC (pin 16 in red) is connected and the two ground pins (pin 4 & 5 in gray). How about the different OBD2 protocols? let’s see:

  • CAN  (ISO15765) used pin 6 & 14 (green color) and they are connected.
  • ISO9141/14230 uses pin 7 & 15 (yellow color) and they are connected.
  • J1850 PWM uses pin 2 & 10 (blue color) and they are NOT connected.
  • J1850 VPW uses only pin 2 (blue color) and it is NOT connected.

So it is clear that this will not support any of the J1850 protocols which are used by most old American car makers (Chrysler/Dodge/Jeep, Ford, GM), luckily I think all new cars (2008+) are using the CAN protocol which is the newest among the others.

Update: Another fake OBD2 reader

I bought another Bluetooth OBD-2 reader that is slightly larger than the one I got before hoping it would have the parts needed to support all protocols and since the seller also claim it does. (Spoiler: I got a full refund).


Guess what? It is exactly the same as the other one, it didn’t work on both of my cars so I opened it up and unsurprisingly it has the same guts (same chips) in slightly different arrangement.

obd2_02 obd2_03 obd2_04

I think having full support is a little too costly even for the Chinese manufacturer, also don’t be fooled by some sellers on Amazon who sell the same exact models for $15+, increasing the price won’t make it work. I also won’t recommend using these basic devices in your car since they don’t have Bluetooth authentication! and any nearby hacker can connect to them and have full access to your car CAN bus and do whatever your car manufacturer has allowed on that bus. You might have heard about the recent car hacks like disabling the breaks and such.

So if you are looking for something that works with all protocols and also safe to use I would go with trusted brands that have been tested by many users, e.g. “OBDLink LX Bluetooth” which looks like the perfect solution, good quality build, support for all ODB2 protocols, sleep mode and has a security button that need to be pressed to allow Bluetooth pairing I have not used it though since it is a little expensive.

28 thoughts on “Inside a fake ELM 327”

    1. unfortunately the answer is no. Since none of the included chips do support that protocol. The only way is to get a chip from a more expensive OBDII wired device and try to integrate it with the bluetooth module, which will mostly require having an interface between them like a microcontroller, but doing that will increase the cost to the point where is it better to simply buy a bluetooth OBDII device that has support already.

  1. by the way,neither the ISO9141/14230 protocol is not working on a Fiat bravo 2007,tried in automatic and manual protocol set.on the same vehicle another obd2 elm327 v1.4 interface is working the sw that I tried just put my airbag computer in error ha ha

  2. I have acquired aand tested a largish sample of low cost OBD2 devices and tested them for J1938 (truck & bus) and CAN with emulators. Only a few devices work.
    If anyone is interested I can provide some test data on different devices

    1. That will be great, since I am still looking for a cheap one that works with my car. I ordered one yesterday, and they claim it works with all protocols, I will update this once i get it and test it.

  3. This is very common in diagnostic tools from China.

    Even “better” ELM327 Bluetooth interfaces (with PIC18xxx insdide, of course not genuine ELM327) have incorrectly wired J1850 PWM and VPW and may result in serious vehicle damage (but somehow it seems to be working, not reliable, but does something ;-) ).

    ISO9141 K-Line is also incorrectly designed, however the bus is more tolerant to any electrical failures.

  4. I am using this on a 2003 Ford Explorer with a Droid Razr and the App called Torque. I was about ready to retrun this item, but then after some internet searching via Torques Help button […] I was able to figure out how to get it to communicate with the Torque app. I would give it a five star if the manufacturer/retailer had included better guidance on getting it to work. I suppose with all the different phones/tablets/apps it’s hard to provide a single, unified set of instructions .1) Plug the ELM 327 device in the OBDII port under the car’s dashboard (it’s directly inline with the steering column on my Explorer).2) Start the car (you probably don’t actually need to do this step to make it work.)3) Go to your smartphone Wireless & Networks settings and turn Bluetooth ON.4) Go to the the phone’s Bluetooth Settings and Scan for Devices and look for CBT to be found, which is the ELM 327.5) Pair with the this device (The code is 1234).6) Then start the Torque app.7) Go to the Settings in Torque and select OBD2 Adapter Settings.8) Pick Connection Type = Bluetooth.9) Go to Choose Bluetooth Device and pick CBT. 10) Suggest also select Auto Bluetooth On/Off and Only if BT was already off. 11) Then go back to the Torque main screen and things should be working!12) Good luck!

    1. That is impossible, the 2003 Ford Explorer doesn’t use CAN protocol which was introduced in 2004 Ford Explorer and later.
      So it is either you have a newer model, or use are using a different reader. The one I showed doesn’t even have the electronics that can understand the old protocols. So Torque or whatever you use will not fix that problem.

      1. OR…. the OP’s Explorer is a late production year ’03, and has ’04 functionality. American manufacturer’s are notorious for doing such things. Some foreign manufacturers are known, or have been in the past, (I’ve been out of the auto repair field for a number of years), for the same issues.

        My wife’s 06 Jetta TDI is a good example. There hasn’t been a part I’ve bought for it yet where the VIN number wasn’t needed to get the correct part. (The VIN provides the production date.)

  5. Have tried two ‘mini’ bluetooth ELM327’s from eBay on my UK 1999 Ford Cougar. Just like this web page suggests, pins 2&10 are NOT connected. The PWM and VPM protocol is not supported even though the listing says it is. Both returned for refund.

  6. Thankyou very much, I have a Ford Couger (PWM) and tried two different units (Same box as yours). First was a transparent blue box then a white like your photos. The white one was even labeled ‘Pro-Scan ™’ and I assumed it to be authentic. Testing the pins 2&10 with a multimeter to gnd or + was open circuit so I didn’t need to open them to verify your findings.
    Have Ordered a Vgate brand which was no more expensive but the listing promises to address the J1850 problem.

    1. Bluetooth Vgate received. Does exactly what it says and costed only a little more. Ford owners take note!

  7. I bought a clear blue one that is identical on the inside to yours, also not compatible with any J1850 protocol. Having a strong preference for “mini” sized OBDII dongles, I bought another one, also mini sized, but different style. This one has a pushbutton on top and says, “Interface Supports all OBDII protocols”. It is different inside, only a single board. Unfortunately, same story, the J1850 pins are unconnected. It looks like to get J1850 requires buying a full size interface such as the BAFX. Does there exist a mini sized dongle which works with J1850?

    1. It is not about the size, if you see my updated post I have tested a lightly bigger model and it has the same components, and if you check the other device I linked to in the bottom of my post you will see that it is still small and has full support which means it needs more advance parts that makes it more expensive.

      1. Sorry, I hadn’t seen your updated post since I found this page via Google search. I know it’s theoretically possible to make a mini-sized unit that has full support for J1850, but as of yet, I haven’t seen one confirmed as having full support yet. I will check out your updated post.

  8. I borrowed a co-worker’s BAFX OBD2 interface and can confirm that it does indeed support J1850 protocols as their Amazon ad suggests: “ONLY the BAFX Products® OBD Reader REALLY works on ALL vehicles located in the USA 1996 & Newer! Many cheaper versions have trouble with the J1850 & CAN protocols even though they SAY they work. Many people buy cheap first but always end up buying ours, because ours works!”
    At under $20 shipped from eBay, it may be a worthwhile option for those who don’t mind the larger size as the price is significantly less than the OBDLink LX. It’s approximately the size of 3 of the Chinese “mini” interfaces stacked end-to-end.

    1. Good find, but for the record, BAFX is cheap because it doesn’t use the original ELM327 chip ( which has full support for all standard protocols. Instead they are using a generic microcontroller (PIC18F2480) programmed to emulate the ELM chip, but as I have read in some forums the emulation is not complete and it has some bugs. But for basic needs it should be OK.

  9. I bought a blue elm327 on ebay 2 years ago. Version says 1.5 and works great. Bought a couple since off ebay they say ver 2.1. Neither work. When i look inside the transparent blue covers i notice my older one has more IC chips inside. Anyway my old one works on all cars. These new ones dont. Wish i could get more older ones. Ive heard that even the ebay listings that say ver 1.5 now are just the new crappy ones hacked to show 1.5..

  10. Which OBDII dongles use the authentic ELM327 v.2.2 chip? The only one that I have been able to find is made in Romania and sold by for 49.00 € ($57.82 US) plus shipping. I can’t guarantee that they are selling what they claim, but they do show a photograph of their circuit board containing an authentic Elm Electronics chip.

  11. Are you sure about the statement that most Chrysler/Dodge vehicles before 2008 used J1850 VPW? I ask because most Chryslers (at least in the 1999-2003 time frame) used Chrysler’s “CCD” protocol, which ran at 7.815 Kb/s and was not compatible with the J1850VPW or PWM. CCD is for the most part obsolete now, but if you Google older images of the wiring of your OBDII connector, pins 3 and 11 used to be assigned to Chrysler CCD. Nowadays they’re labeled “Vendor Option”. I know this because I have been looking for CCD info/software/hardware out there and have had a hell of a time trying to find anything.

    1. That is why i said most ;). The J1850 protocol was introduced in 1998 to replace CCD, so not all cars where replaced immeditely. So maybe your car was still using CCD.

  12. How is one supposed to buy a genuine ELM327 diagnostic kit? The market is swamped with garbage. It’s like trying to find the diamond in a bucket full of zirconias!

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