OBD2 Connection Issues

[Ekim]

Hi Team

I am having issues with OBD2 scanner connecting to my G4X V4 WRX Plugin ECU.

My scan tool has 3 LEDs: Red-Power, Green-network, and Blue-Bluetooth.

It is wired up to CAN2 and the OBD has be set to "ISO 15765 on CAN 2" in CAN setup.

But with this setting turned on nothing happens (only the red & blue LEDs and the slow green polling flash) UNLESS I click the "CAN Devices" tab and click "Find Devices" button.  As soon as I do this the OBD2 scanner comes to life (Fast flashing green led) and Scanner works perfectly as expected.

Obviously having to connect my PC and click the "find Devices" button every time I want to use the OBD2 is self defeating, is there any setting that I have missed? If not, can I make CAN2 transmit something to wake everything up?

Subaru WRX V3-4 -5.22.pclx

[Adamw]

I just tested on the bench and it works correctly for me.  Can you attach your map so I can take a look. 

I dont really see why the find devices command should have any effect, all that happens when you hit this button is the ecu sends out a whole lot of CAN keypad "wake up" messages while looking for a response from one.  

Have you got mode set to user defined and bit rate set to 250 or 500K?    

[Ekim]

Hi Adamw,

The bit rate is set to 500k, once again it works OK once the two devices start talking.

I've attached the map to the the original post

[Adamw]

I have just loaded your map into a plug-in ecu and tested with a generic Chinese ELM327 USB dongle and a PLX kiwi Bluetooth dongle, they are the only OBD2 devices I have in my office.  I tested with realdash and an old obd2 software called scantool.net, both devices and both softwares connect as soon as the ecu powers up.

So I can only assume there is something a bit odd with your dongle, maybe it defaults to a standby mode or something until it sees bus traffic?  

What you could try is just turning on one of the transmit streams so there is always traffic on the bus to see if that wakes it up.  

Try something like this:

 

[Ekim]

Thanks your help, I will give it a go.

The OB2 reader is the only thing on CAN2, would I need to add a termination resister to the loom?

thanks

 

[Adamw]

It should have one but I doubt that is your issue if you get data ok once it does start.  I didnt have a terminating resistor or even twisted wires in my test, 500K is usually pretty forgiving too.

[Ekim]

Hi again

I tried some other adapters and tried some other software but with no luck but I did make some progress.

While trying to connect with different software and different adapters I discovered I could connect but only within a second or two of the ecu powering up, if I didn’t connect during this time the adapter would never connect.

so typically I would attempt to connect with this sequence 

1. Plug in adapter 
2. power up ecu
3. connect to adapter using car scanner app
4. attempt to connect to the ecu.

this always failed unless I also connected to the ecu with my computer and and scanned the CAN bus as described above. 
 

so my new sequence was like this

1. Plug in adapter 
2. connect to adapter using car scanner app
3. attempt to connect to the ecu
4. power up ecu

this sequence worked is as long as I attempted to access data within a couple of seconds of the ecu powering up otherwise it would not work.    Although this is a workaround it is not very convenient. If I then disconnect the ecu in the app and reconnect the connection will fail.

it seems to me that the CAN bus looks for data traffic during ecu startup and if it doesn’t find any it simply stops listening to the CAN bus. My Can Scanner app allow me to send command is there an initiation command I can send the ecu to wake it up?  Is there a CAN bus timeout that can be set longer than a couple of seconds?

[Adamw]

Can you attach a copy of your map and attach a short PC log of the OBD2 connection failing.  

[Ekim]

Hi Adam

Here are the files you requested.

As you can see from the logs the ECU just stops responding unless I reset the ECU.

Cheers

Subaru WRX V3-4 -5.22.pclx Restart ECU after connection hack.txt Failed to connect log.txt Connected but failed to operate.txt

[Adamw]

Can you attach a PC Log (from PC Link).  Your map shows 128 transmit errors on CAN 2 and bus passive error when it was last saved, it will disable the bus once it gets to 248 transmit errors.  Resetting the ecu or clicking apply in the CAN set up screen will reset the CAN controller which resets the transmit error counter so that's why it starts working again.

The question is, why is the device not acknowledging the transmits?  Do you have a terminating resistor wired?  

[Ekim]

Hi Adam

I have just added a termination resistor and it made no difference.

Is there a particular parameter(s) you want me to log? or specific log file?

 

I have uploaded a CAN log, Starts off error free, then I attempt to connected with OBD2 adapter ~18secs and then reset the CAN at ~47secs

PC Datalog - CAN reset after OBD2 connection.llgx

[Ekim]

Hi Adam 

have you had a chance to look at this?

cheers

[Ekim]

Solved, I’ll post on the off chance this helps someone else. 
the Link ECU seems to have a problem with the software requesting VIN information, this option should probably be switched off on your software, mine was but it seemed to request it anyway. I could replicate the issue by querying the ecu’s VIN information manually. 

So the VIN issue would create an error on the bus and the OBD2 software was setup to re-initialise if it encountered an error.  So the OBD2 software was trying to re-initialise while the link ECU was happily transmitting data and not responding as expected and creating a cascade of errors until the Link shuts down the bus.  So the solution was simple just set the OBD2 software to ignore errors ( default was to reconnect + initialisation).

job done.