OBD2 Port Question - Blue Wire?

[Lowe712131]

Having trouble hooking my SL55 up to a remote tuning program - the software just doesn't seem to want to communicate with the car for some reason. Everything seems correct in the software & hardware setup, but it just won't see it. Had similar issues with some of the features through STAR too, can't seem to connect with all the modules. My suspicion is there may be water damage on one of the CANbus connectors - one of which connects to the diagnostic port, but I can't be sure until I get time & weather to get the seats out and have a good look around. In the meantime though, I popped the panel off the right side of the dash (so you can see the back of the OBD2 port) and there is a stray blue wire there. I can't see any connections missing a wire and the end of it is taped up, but I was wondering if anyone had seen this before and knows what it is? The wire doesn't seem to be part of any loom but it seems strange it's sat there not connected to anything. Any ideas?
Cheers
Simon

 

[DennisTheMenace]

Is the wire soldered into an existing wire or occupying a pin?

You can check your CAN with a multimeter, set it to dc volts, find a good earth and check the voltage of CAN H and CAN L. CAN High voltage should be more than CAN Low.

Also set the multimeter to ohms and bridge CAN high and CAN low, resistance should be around 60 ohms.

 

[television]

There is a fuse for the OBD port.

You can access the CAN in the connector behind the driver seat.

CAN L runs at 11volt when dormant and 4.65volt when active
CAN H runs at 0.25 volt when dormant and 0.25volt when active

No terminating resistor

 

[Lowe712131]

Stray blue wire

Thanks for the replies, I have a break-out box to test the voltages - am I correct in saying it is pin 5 for signal ground, pin 6 for CAN H and 14 for the CAN L? One slight question with this though, are these pins (on OBD port) for CAN C? DO you have to measure the voltages on the CAN connector to measure CAN B (which is the one I need, I take it, for body electrics?) Sorry if this makes no sense, trying to get my head into this, it's new to me.
Cheers
Simon

oh, and the blue wire doesn't seem to belong anywhere, no pin or solder, just tape on the end of it - possible some aftermarket thing that has been removed, maybe. I'll try and trace it when I get time/weather or my garage back!

 

[television]

The master of the CAN is the EIS switch. CAN B starts here going through X30/15, 16 and 17, it then goes to the diag socket ,the wires are, brown and brown/red

 

[Lowe712131]

Thanks Guys. I'll make sure to post results when I've had chance to meter it. Managed to get the remote tune sorted in the end, Jerry from Eurocharged in the States logged into my PC remotely whilst connected to the car, sorted the communication issue and re-flashed the ECU over the net! Most impressive. Good service from CKS Motorsport in Watford, was experiencing a Speedtronic fault after remap, couldn't get the car down to them so I loaned a remote tuning cable off them and Eurocharged sorted it. Good experience