Hi everyone. I have some trouble understanding the pinout of my OBDII plug. It appears that it has both grounds, K-Line, 12V and CAN Bus low (according to standard obdII plug). Therefore it does not have even one complementary pair of signals. Yet, when I plug my Bluetooth OBDII scanner it communicates with ECU correctly. I have never noticed that before my ABS light came on. I was checking if in my 7th gen Civic there is a so-called Service Check System pin to force ABS light to communicate error codes in pulses. A bit puzzled by the pinout of my OBDII plug. Could someone explain the meaning of each pin? Thanks!

 

Honda of this generation pre dates CAN. Scan tool does all of it's communication on single wire K line.

I think it is pins 4 and 7 get connected for the blink codes. Or was it 4 to 9.

 

@Ryanthegreat1 Thank you for your reply. Yes, I heard about shorting pins 4 and 9 to get diagnostic codes using the dashboard cluster. When I looked at the port in my car I got puzzled as pin 9 is missing. There are only 5 pins in my car these are pins: 4, 5, 7, 14 and 16 if I read them correctly. If these were OBDII pins they would be as follow:
4 CGND Chassis ground
5 SGND Signal ground
7 K-LINE (ISO 9141-2 and ISO/DIS 14230-4)
14 CAN Low J-2284 (WEN)
16 +12v Battery power (unswitched)
However, as you stated my car pre-dates CAN I suspect that pins 7 and 14 have different roles. I am hesitant to short anything before finding out what they are for. With both grounds and +12V, I can easily check using DMM. I could try to hook up the oscilloscope to pins 7 and 14 to see what I get. This however would require some time to get my hands on the scope and set it up. Could I check it without an oscilloscope somehow?

 

Just read this… which describes exactly the problem I am experiencing with my ELM327.

https://typeaccord.co.uk/board/threa...7th-gen.23506/

" On the 7th gen, HDS (or an ELM327) uses K-line. There is a K-line connection to the MICU (which acts as a proprietary gateway to CAN which HDS can read but some ELM327 cannot read). There is also a K-line connection to pin 23 on connector E of the engine ECU (not easy to find in the ESM) which is for direct reading of the engine ECU as provided for in the OBD2 standard (hence cheap generic readers can read the 7th gen engine ECU but nothing else)."
In other words, on the 7th gen pre-facelift (and probably the facelift) only the K-Line connection to the ECU is fully OBD2 compliant, the other K-Line connection to the MICU (which is the gateway to the other ECUs on the CAN) is proprietary.
Thus if you buy something that does not explicitly say that it can read the ABS etc on a 7th gen Honda Accord, then you may be disappointed.

 

Ah, yes. Generic OBD readers will not read beyond the engine stuff on a Honda. You need a Honda specific scanner to talk to ABS and SRS and all the other things.

Still not technically CAN bus. It doesn't use the CAN protocol.

 

I checked the pins with DMM and the voltages are as follows: Pin 4 0V, Pin 5 0V, Pin 7 12V, Pin 14 5V, and Pin 16 12V.