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

OBD2_pinout

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).

obd2_01

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.

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22 Comments on "Inside a fake ELM 327"

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fordwrench
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fordwrench

Is there anyway to fix for 1850 protocol.

pierre
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pierre

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 good.al the sw that I tried just put my airbag computer in error ha ha

Robin
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Robin

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

Admin
Admin

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.

Lee Wilkerson
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Lee Wilkerson

Robin, I am very interested in having a copy of that list. 1(734)757-0579

Martin Hinner
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Martin Hinner

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.

Walker
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Walker
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… Read more »
XCX
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XCX

just some seller spamming his manual

GeoNOregon
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GeoNOregon

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.)

Martin
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Martin

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.

Martin
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Martin

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.

Martin
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Martin

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

Shawn
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Shawn
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?
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