[Ovmsdev] OVMS ODBII Cable

Mark Webb-Johnson mark at webb-johnson.net
Tue Nov 13 08:43:03 HKT 2012


The Tesla Roadster has two connectors - (1) a proprietary connector for 3 CAN buses that we call DIAG, and (2) an OBDII port.

OVMS uses the DIAG connector to get access to a single CAN bus that contains the messages we need.

I recall that by law, all cars sold in USA must have an OBDII connector and it is found close to the steering wheel (something like within 2 feet?).

Regards, Mark.

On 13 Nov, 2012, at 6:08 AM, HONDA S-2000 wrote:

> Just to clarify, would this work for the Tesla Roadster? Looking at the photo, the connector looks different. Does that mean the Tesla does not have an OBD2 connector? Is it the older OBD? Is it something that only Tesla uses for diagnostics? Sorry for all of the questions, but I've never connected anything to OBD ports on any of my cars, even though I'm aware of lots of products that are available. The OVMS is my first.
> Brian
> On Nov 12, 2012, at 03:09, Mark Webb-Johnson wrote:
> I've found a couple of manufacturers willing to do this for a reasonable price (at a quantity of perhaps 50 to 100 units).
> Is the specification below ok? Any problems?
> Regards, Mark.
> On 11 Nov, 2012, at 1:36 PM, Mark Webb-Johnson <mark at webb-johnson.net> wrote:
>> OK, so I think the pinouts we require are as per Michael B's diagram:
>> J1962-M		DB9-F		Signal
>> 4		3		Chassis/Power GND
>> 6		7		CAN-H
>> 14		2		CAN-L
>> 16		9		+12V Vehicle Power
>> A right angle J1962-M plug and about 1metre cable should be ok.
>> This one cable should support both Twizy and Volt/Ampera, and also any ODBII car with an ODBII compliant CAN bus.
>> Does that sound ok?
>> On 11 Nov, 2012, at 7:50 AM, Michael Balzer <dexter at expeedo.de> wrote:
>>> For the record: I now have connected GND to both 4+5 on the OBD2 plug, works as well.
>>> Am 10.11.2012 19:57, schrieb mikeljo at me.com:
>>>> i use this pinout:
>>>> Primary Data Link Connector- (DLC) X84 *Under drivers side of IP
>>>> Pin 1 is Low Speed GMLAN (SWCAN ~33.3kbps) - Body Electrical Services Only Pin 2-3 Unused
>>>> Pin 4 chassis ground (for scan tool)
>>>> Pin 5 data reference ground
>>>> Pins 6(+) & 14 (-) High Speed GMLAN- Primary Powertrain Bus (DWCAN ~500 kbps) Pins 7-11 Unused
>>>> Pins 12(+) & 13(-) High Speed GMLAN- Chassis Expansion Bus (DWCAN ~500 kbps) Pin 15 Unused
>>>> Pin 16 B+ (for scan tool power)
>>>> OBDII            Sub-D Signal
>>>> 16 9 +12V
>>>> 4 6+3 GND-Chassis
>>>> 6 7 CAN_H
>>>> 14 2 CAN_L
>>>> I connect 6 and 3 at the Sub-D side together.
>>>> So it looks like we can use the same Cable (for the Primary Can Bus in the Volt). >> Fasttech?
>>>> Am 10.11.2012 um 06:47 schrieb Mark Webb-Johnson <mark at webb-johnson.net>:
>>>>> Yes, chassis GND vs signal GND, but can is differential, so no GND needed for the signal. We only need GND for 12V power. For vehicles, I think chassis GND is ok.
>>>>> I think Volt bus we are using is on the same pins:
>>>>> http://www.evtools.info/ChevyVoltOBD2CAN.html
>>>>> Maybe 1 cable can do both?
>>>>> On 10 Nov, 2012, at 12:18 PM, Michael Balzer <dexter at expeedo.de> wrote:
>>>>>> yes, that's chassis ground -- shouldn't it be? I interpreted the OVMS GND as the ground for the supply voltage (12V), as the CAN bus has its dedicated "low" line.
>>>>>> I just looked up some OBD2 sites: 4+5 normally are the same. One page says an OBD2 cable should have identical potential on 4 and 5 to ensure proper function. Another OBD2 cable I bought connects them, so maybe for a general product GND should connect both, but I don't think there's a difference on the car side... normally.
>>>>>> But I've also seen some info on non standard OBD2 plugs, also for some GM and Opel cars, having other signals where the CAN bus should be, so I'm also interested in your pinout, Michael J.
>>>>>> Am 10.11.2012 04:23, schrieb Mark Webb-Johnson:
>>>>>>> One question: you have GND on pin #4 (odb). I have that shown as chassis ground, not signal ground. Is that correct?
>>>>>>> Michael J: is that the same connector and pins as you are using for the Volt?
>>>>>>> Regards, Mark
>>>>>>> On 10 Nov, 2012, at 2:16 AM, Michael Balzer <dexter at expeedo.de> wrote:
>>>>>>>> 1) I just created an OVMS to OBD2 cable image and checked it in:
>>>>>>>> https://github.com/dexterbg/Open-Vehicle-Monitoring-System/commit/a7c3a3e8f12d7759b896bb75c8e570ebc10ec11a
>>>>>>>> As OBD2 is standard incl. CAN pinout, this should be valid for any OBD2 port, so could be added to the FastTech OVMS product line. It's not a standard cable, or at least none I know of.
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