I'm a research engineer working on OBD2 scanner, I'm using ELM327 v1.5 interface to communicate with cars. I used Dacia Logan 2013 (French car) to test OBD2 modes, the MIL indicator was ON.

When I test mode 3, I get this response (image below) 3 bytes after 43

GUI created with Qt c++

But when I checked the datasheet of ELM327 (https://www.elmelectronics.com/wp-content/uploads/2016/07/ELM327DS.pdf page:34) it must be 6 bytes after 43 to read it in pairs every 2 bytes represente a DTC.

How to interpret my OBD2 response?


It's a problem of protocoles, the car uses the CAN (ISO 15765) protocol.

Some of OBDII protocols (J1850, ISO9141, and ISO14230) do not show the number of trouble codes in Mode 03 response, so the interpretation of the response are the same as in page 34 of the ELM327 datasheet.

But the protocol CAN (ISO 15765) does show the number of DTCs.

So the interpretation of 43 01 01 2C is :

43: response of mode 3

01: one troube code stored

01 2C : the trouble code P012C (dtcsearch) / P012C (obd-codes)

I get this Information from the elmelectronics technical support team


I have worked with embedded systems and OBD2 for 2 large OEMs. The ELM327 is the cheapest tool you can buy and it shows.

I'm not even recommending a vehicle-specific or expensive tool, just try spending more than $10 on one. Look into OBDlink or Foxwell devices. The ELM327 we had was primarily used to prop up a soldering table.

  • This question was posted the other day on electrical I think , I gave basically the same advice, along with the detail that manufacturer’s make and use their own codes over and above the standard ones. – Solar Mike Jan 22 '18 at 12:27
  • I completely agree, ELM327 is old, slow and over rated. Anyone with basic electronics knowledge and reasonable software skills can build their own interface which is faster, easier to work with fully customisable with a simple MCU and a CAN bus transceiver. But like you said just on Ebay and buy a device for more than a few £/$/€ – Terry Gould Jan 22 '18 at 12:34

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