If you are new to DIY car repair or trying to figure out what that yellow MIL lamp represent, this post is for you. This post is a short intro on ODB2 and cheap car diagnostic tools like ELM 327 and VCDS. Majority of error cods can be fixes easily and do not require complex service. On the average ELM costs about $20-30 and VCDS (VAG COM) from $20-350. I will only cover cables that connect to PC and not handheld units, from my experience PC versions are more particle and can be used with different software giving you flexibility.
As of 1996 all car have have to OBD-II compliant vehicle. There are five communication protocols: J1850 PWM, J1850 VPW, ISO9141-2, ISO14230-4 (also known as Keyword Protocol 2000), and more recently, ISO15765-4/SAE J2480 (a “flavor” of CAN). US car manufacturers were not allowed to use CAN until model year 2003, but as of model year 2008 and going forward, all vehicles will use the CAN protocol. ODB-II port looks like this
PWM The connector must have pins 2, 4, 5, 10, and 16
VPW The connector must have pins 2, 4, 5, and 16, but not 10.
ISO The connector must have pins 4, 5, 7, and 16. Pin 15 may or may not be present.
CAN The connector must have pins 4, 5, 6, 14, and 16
ODB in you car is located: Database of ODB connectors
Now, you might ask you self, which ODB cable should I get?? From my experience all of these protocol can be utilized by these two cables. If you own US/Japan made car then get ELM 327 cable, if you have VW / Audi then get VCDS cable.
What is ELM 327:
ELM 327 cable supports all of above protocols and can be considered as universal cable if such thing exist. These cables cost only $20-30 and are cheap way to get started with ODB code decoding… At this moment 1.4 version is most current. These cable have USB and Bluetooth version as well (get blue-tooth for Ipone interface). For Windows 7 ELM drivers visit my other post.
Good source for ELM 327 cables is ebay, they are cheap and easy to find…
The free version is scan tool, the software that I like are Scan Master ELM (75 euros) and ODB spy. If you ask me, Scan Master is the best ELM 327 software, giving you wide range of tools and charts.
note: for some newer VW and AUDI cars ELM 327+Scan Master will work as well (I think its 2006 and newer). ELM 327 is to fast for most older VW and Audi cars and needs to be slowed down under Option/Communication/baud rate (start with 9600 bps)
+ Scantool 1.21 (free)
+ Easy OBDII 2.4.0 (free)
+ OBD2Crazy wOBD 1.40 (free)
+ List of other relevant software
ELM 327 Links
Fiat and ELM 327 software
ELM 327 tech specs
Make your own with LCD
Make your own Can get parts from website for $35.
ELM 327 Can Bus IC
Torque for Android
yhasi.com For Mac OS X ELM 327 software as well.
VCDS and VAG-COM
VCDS is great tool for VW and Audi cars, you can diagnose car code and performance testing. The best part is that you “adapt” parameters on your car like: daylight running light, auto lock, height of your car, and etc.
The original cables can be found at link. For $350 you get original software VCDS and cable. On Ebay and some other website you can find Chinese version of these cables simply called VCDS clone, at this moment version 11 is current. The Chinese version of this cable cost only $20-30. I use this cables with great results, just keep in mind that you can not upgrade these cables or use any other version than they are marked for.
note: Do not get VAG-COM KKL 409 (blue), this is old cable that works only on older and slower on-board computers. Some people have converted the 409 to great Fiat and Alfa Romeo diagnostic tools (some soldering required).
If you just starting with this, get ELM 327 since its cheap and can be used for many different brand of cars.
Build your own ODB reader DIY / PIC
The hardware consist of the 2 main ICs (integrated chips) – dsPIC33FJ128MC802 (3.3V) and MCP2551. Alternative device could be PIC18F4585 (5V) or dsPIC30F4011 (5V) etc. Link