cwpaynter
Posts: 4
Joined: Tue May 28, 2019 9:06 pm
Delivery Date: 29 May 2019

Re: LEAF CANbus decoding. (Open discussion)

Tue May 28, 2019 10:15 pm

On my 2019 Leaf, I'm monitoring the DLC connector near the steering wheel, pins 6 & 14, trying to see the primary CAN bus data. Using an oscilloscope, I'm not seeing any data at all on either line, they're both sitting at the recessive voltage of about 2.5.
Everything I've read suggests there should be bits flying out of that connector, but for me they're just flat. If I plug in my LeLINK ODB adapter, LeafSpy is able to read all the usual stuff.
I'm thinking I'm doing something really wrong here - anybody seen this before? Wondering if I've badly misunderstood the nature of that bus.

lorenfb
Posts: 2222
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 8:00 am

cwpaynter wrote:On my 2019 Leaf, I'm monitoring the DLC connector near the steering wheel, pins 6 & 14, trying to see the primary CAN bus data. Using an oscilloscope, I'm not seeing any data at all on either line, they're both sitting at the recessive voltage of about 2.5.
Everything I've read suggests there should be bits flying out of that connector, but for me they're just flat. If I plug in my LeLINK ODB adapter, LeafSpy is able to read all the usual stuff.
I'm thinking I'm doing something really wrong here - anybody seen this before? Wondering if I've badly misunderstood the nature of that bus.


Check here: http://www.mynissanleaf.com/viewtopic.p ... 96#p239692

Remember, the CAN bus produces a differential signal between the two pins. When inactive, both pins are at 2.5 volts.
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F (35C), min discharge (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 25%, temp < 105F

cwpaynter
Posts: 4
Joined: Tue May 28, 2019 9:06 pm
Delivery Date: 29 May 2019

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 8:14 am

Yes, that's the problem, both lines are at the recessive 2.5 volts, indicating no data on the bus. I expect to see CAN hi going up to about 3.5 volts for a dominant bit, and CAN lo going to about 0V, but they're both steady at 2.5V. That LeafSpy still works indicates to me that the CAN bus is functional and I'm just not using it right. In my case I have a short odb cable plugged in with the scope ground on 4 or 5, and the probe on pin 16 or 4. I've also tried a differential measurement with the scope ground on CAN lo and the probe on CAN hi, there's essentially no voltage between them. (The scope's earth ground is floating due to a missing ground pin on the extension cable from the house)

I don't see why no data should be coming out, but I wonder if the DLC connector needs to have a couple pins shorted to indicate that it should become active? Or perhaps I misunderstood the bus, and have to request every message? I understood that the various modules are all transmitting stuff to each other, and that I would be able to see that data whizzing by.

lorenfb
Posts: 2222
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 8:36 am

cwpaynter wrote:Yes, that's the problem, both lines are at the recessive 2.5 volts, indicating no data on the bus. I expect to see CAN hi going up to about 3.5 volts for a dominant bit, and CAN lo going to about 0V, but they're both steady at 2.5V. That LeafSpy still works indicates to me that the CAN bus is functional and I'm just not using it right. In my case I have a short odb cable plugged in with the scope ground on 4 or 5, and the probe on pin 16 or 4. I've also tried a differential measurement with the scope ground on CAN lo and the probe on CAN hi, there's essentially no voltage between them. (The scope's earth ground is floating due to a missing ground pin on the extension cable from the house)

I don't see why no data should be coming out, but I wonder if the DLC connector needs to have a couple pins shorted to indicate that it should become active? Or perhaps I misunderstood the bus, and have to request every message? I understood that the various modules are all transmitting stuff to each other, and that I would be able to see that data whizzing by.


That CAN pair just isn't being accessed. Try looking at the other CANs referenced in the link. Avoid shorting pins. You can back-probe
the connector when LeafSpy is connected to verify a signal.
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F (35C), min discharge (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 25%, temp < 105F

caederus
Posts: 12
Joined: Sun Mar 20, 2016 9:34 am
Delivery Date: 01 Mar 2016

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 9:09 am

cwpaynter wrote:On my 2019 Leaf, I'm monitoring the DLC connector near the steering wheel, pins 6 & 14, trying to see the primary CAN bus data. Using an oscilloscope, I'm not seeing any data at all on either line, they're both sitting at the recessive voltage of about 2.5.
Everything I've read suggests there should be bits flying out of that connector, but for me they're just flat. If I plug in my LeLINK ODB adapter, LeafSpy is able to read all the usual stuff.
I'm thinking I'm doing something really wrong here - anybody seen this before? Wondering if I've badly misunderstood the nature of that bus.

I only had a 2019 LEAF briefly on a test drive, so didn't have much time to poke about, but using the cable I have for my 2016 LEAF and OVMS module, the only packets I logged were active requests and replies on addresses 7XX. I didn't see any routine CAR or EV bus packets on addresses 0XX--6XX, as I would normally expect in the older models. So my guess is that the 2019 OBD port is connected to some gateway device which will only relay 7XX traffic.

lorenfb
Posts: 2222
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 9:21 am

caederus wrote:
cwpaynter wrote:On my 2019 Leaf, I'm monitoring the DLC connector near the steering wheel, pins 6 & 14, trying to see the primary CAN bus data. Using an oscilloscope, I'm not seeing any data at all on either line, they're both sitting at the recessive voltage of about 2.5.
Everything I've read suggests there should be bits flying out of that connector, but for me they're just flat. If I plug in my LeLINK ODB adapter, LeafSpy is able to read all the usual stuff.
I'm thinking I'm doing something really wrong here - anybody seen this before? Wondering if I've badly misunderstood the nature of that bus.

I only had a 2019 LEAF briefly on a test drive, so didn't have much time to poke about, but using the cable I have for my 2016 LEAF and OVMS module, the only packets I logged were active requests and replies on addresses 7XX. I didn't see any routine CAR or EV bus packets on addresses 0XX--6XX, as I would normally expect in the older models. So my guess is that the 2019 OBD port is connected to some gateway device which will only relay 7XX traffic.


Yes, like most later vehicles, e.g. M/B, BMW, Porsche, the Plus most likely has a central gateway to access other ECUs not directly
connected to the OBDII connector, but are on slower speed single-ended low speed bus, e.g. inst cluster.
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F (35C), min discharge (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 25%, temp < 105F

virol
Posts: 21
Joined: Sun Sep 23, 2018 9:38 am
Delivery Date: 17 Sep 2018
Leaf Number: 2018
Location: Belgium

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 10:25 am

caederus wrote:
cwpaynter wrote:On my 2019 Leaf, I'm monitoring the DLC connector near the steering wheel, pins 6 & 14, trying to see the primary CAN bus data. Using an oscilloscope, I'm not seeing any data at all on either line, they're both sitting at the recessive voltage of about 2.5.
Everything I've read suggests there should be bits flying out of that connector, but for me they're just flat. If I plug in my LeLINK ODB adapter, LeafSpy is able to read all the usual stuff.
I'm thinking I'm doing something really wrong here - anybody seen this before? Wondering if I've badly misunderstood the nature of that bus.

I only had a 2019 LEAF briefly on a test drive, so didn't have much time to poke about, but using the cable I have for my 2016 LEAF and OVMS module, the only packets I logged were active requests and replies on addresses 7XX. I didn't see any routine CAR or EV bus packets on addresses 0XX--6XX, as I would normally expect in the older models. So my guess is that the 2019 OBD port is connected to some gateway device which will only relay 7XX traffic.


@caederus

have 2018 leaf tekna 40kw, can you explain exactly how to send an active request on 7xx adresses with a ELM module over the ODB plug.
you may also PM me

cwpaynter
Posts: 4
Joined: Tue May 28, 2019 9:06 pm
Delivery Date: 29 May 2019

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 11:17 am

Thank you for the suggestions folks, I didn't see any traffic on the other CAN buses either, but I now have a few strategies to try tonight:

    try to transmit requests on the bus using a Pycom LoPy4 board with a CAN transceiver
    use the same hardware to drive around and see if that stimulates any traffic
    borrow a buddy's CAN -> USB dongle and sniff using that, and possibly transmit requests.

caederus
Posts: 12
Joined: Sun Mar 20, 2016 9:34 am
Delivery Date: 01 Mar 2016

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 12:14 pm

virol wrote:have 2018 leaf tekna 40kw, can you explain exactly how to send an active request on 7xx addresses with a ELM module over the OBD plug.

LEAF active queries and replies use UDS over ISO-TP. Unfortunately the wikipedia documentation is incomplete, and the addresses and data bytes are not defined by the standard anyway, so are all informed guesswork.

A simple example would be reading the odometer, where both query and reply each fit in single packets:

Code: Select all

Query: 743#022119FFFFFFFFFF
Reply: 763#056119005D6AFFFF

743 is the query address for the instrument cluster
The first data byte 02 is the ISO-TP header:
- 0 in the upper 4 bits means that this is a single ISO-TP packet.
- 2 in the lower 4 bits means there are two UDS data bytes (21 19):
- - 21 is the UDS service ID "Read data by local ID", which takes one parameter
- - 19 is the local ID, which the instrument cluster interprets as odometer.
The remaining FF bytes are padding.

763 is the reply address (for the instrument cluster)
The first byte 05 is the ISO-TP header:
- 0 in the upper 4 bits means that this is a single ISO-TP packet.
- 5 in the lower 4 bits means there are five UDS data bytes (61 19 00 5D 6A)
- - 61 19 is the same as in the query, with 0x40 added to the service ID to indicate it is a reply.
- - 005D6A is the odometer reading.
The remaining FF bytes are padding.

ybpvin
Posts: 9
Joined: Fri Aug 24, 2018 4:55 am
Delivery Date: 24 Aug 2018
Leaf Number: 022135

Re: LEAF CANbus decoding. (Open discussion)

Wed May 29, 2019 9:41 pm

I wonder, thank you. how can I read the byte eeprom dashboard?

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