2004 Accord EX L 2.4L. Automatic. 283,000 mi. Unmodified. Original owner.

So, connected my scanner to diagnose an ABS light and got a “can’t communicate” message. Tried another scanner and a friend’s scanner. No luck. Took to Honda (who were awesome BTW) and they tried 3 scanners and checked all the fuses. Still no luck.

I performed a diagnostic procedure I found on line to check wiring and it suggested a bad ECU. Got another ECU and installed it. Everything seems to function except actually starting the car (expected since keys not reprogrammed) but still no communication with scanner.

Any suggestions?

I’d be happy to rerun the wiring diagnostics if someone has the procedure for this year and model. Maybe the one I did was not correct.

Also, does anyone have wiring/ pin outs for DLC and ECU on this car?

Car runs great and I wouldn’t really care but recently moved to a location that requires an inspection that includes checking the codes.

Thanks in advance for any help. I’m kinda at a loss here.

 

Is the port still clipped in its original location or freely moving. If so I would check the wiring at the port and if a wire is bad just push the female pin out and redo it.

 

Along the same lines, check for obvious damage to the pins in the connector and wiring.



You may want to use a volt meter to check the DLC connector wiring. Do not jump any wires and only use the voltage setting and continuity setting.

Not all of the pins are used in the 16 pin connector.

I know there will be one pin with 12V and another one that should have ground.

The other pins are for data reading/transfer.

For my TSX here are the wire colors for the pins at the DLC.

16 wht/grn Hot 12V
14 gry Immobilizer
12 red/wht ECU E30
09 brn ECU E29
07 blu ECU E23
05 blk Ground
04 blk Ground

If the wire colors match up you can check for voltage from 16 to a ground. For 04 and 05 test for continuity to a good ground point. I try to find some a bolt or some bare metal to touch my volt meter to ground.

 

Thanks for the pin info. I will recheck the pins at theDLC as well as rechecking the voltages and grounds.

Does anyone know what the signal pins translate to on the ECU plugs? I’d like to check the continuity of those also.

Thanks.

 

Oops. I see you included that info! It’s early and I’m recovering from the vaccine!

Thanks!

 

That pin info is for my acura tsx, so your accord pins may be different.

You may want to get the factory service manual for your car. You can get a pdf from automanualsource.com for ~$22 and is worth every penny for diy work.

 

I wanted to provide an update.

I got another ECU and tried it and still could not communicate.

I did verify that the pin outs provided for the TSX match the Accord. I actually did a wire by wire continuity and ground check to confirm the integrity of the wiring.

Searching around the internet, I found a video by Scotty Kilmer where he recommended disconnecting various sensors one at a time until you found the one that was failed and thus preventing the scan tool from talking to the computer. Since I had an ABS light, I disconnected the plug from the ABS controller and was able to communicate to the ECU. Of course the problem now is that I cannot use the scanner to find out what is wrong with the ABS. I suspect a failed wheel speed sensor from when I replaced axles but I guess I won't know until I replace those.

It seems a little silly that a failed sensor will prevent you from talking to the ECU since the whole point of the OBD is to point you to the fault. Oh well.

Good news though is that I SHOULD now be able to get the car inspected so I can renew the registration.

Thanks to Scotty for posting that video and thanks for the help provided here.



I hope this helps someone in the future.

 

What a life saver you've been my friend. Your last post probably saved me hundreds of dollars. Had taken my Accord 2005 to several shops due to no communication between ECU and scanner.

All kinds of theories and tests. Was about to take ECU to electronic shop for fixing or get a new one. Had searched extensively online for solutions and was about to give up.

And then I found your post - my ABS light had been activated for a couple of weeks also. Disconnected the ABS module and amazing!! The scanner worked. Thanks again for taking the time to include the solution you found in that last post. God Bless and take care..

 

Maybe I'm thick, can you tell me where to disconnect the ABS module or how? 2003 accord ex coupe.

thanks

 

Can you descibe how to disconnect the ABS module...pass side of vehicle?

thanks
jay