Honda SEFMJ protocol

Hardware inside and outside of the ECU
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AndreyB
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Honda SEFMJ protocol

Post by AndreyB »

Trying to make a PnP for 2004 Honda Civic Si with K engine. Last frontier is A/C control and dash coolant temperature gauge.

I am stuck and confused about pin E24 called SEFMJ, it runs between ECU and multiplex control unit.

* At the moment I am still not sure if that's a uni-directional serial or bi-directional something
* if it's a bi-directional then what is it? we have k-line tja1021 circuit which seems to work on Mazda but did not pass through SEFMJ traffic.

wiring diagram https://github.com/rusefi/rusefi_documentation/raw/master/OEM-Docs/Honda/2003-acura-rsx-type-R.pdf

A/C diagram attached
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mck1117
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Re: Honda SEFMJ

Post by mck1117 »

have you scoped that pin on a working unmodified car?
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Re: Honda SEFMJ

Post by AndreyB »

So many hints on the internet but nothing definitive

hondata mention that pin could be repurposed as serial output http://www.hondata.com/help/kmanager/index.html?serialoutput.htm

AIM says pin is ECU *output* but how would A/C request work if it's only output?! https://www.aemelectronics.com/sites/default/files/aem_product_instructions/30-6030%20Series%202%20Plug%20%26%20Play%20EMS.pdf

http://www.race-technology.com/forum/viewtopic.php?t=2079 says it's a custom RS-232?!

mentions k-line
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Re: Honda SEFMJ

Post by AndreyB »

mck1117 wrote:
Sat Mar 04, 2023 12:47 am
have you scoped that pin on a working unmodified car?
logic analyzer snippet in first post is from working car, with resistor divider. A couple of photos of same, on unmodified car.
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Re: Honda SEFMJ protocol

Post by mck1117 »

well it's certainly 9600 baud 8n1 serial, probably bidirectional on that one line. So it's effectively LIN/kline.
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Re: Honda SEFMJ protocol

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Re: Honda SEFMJ protocol

Post by AndreyB »

mck1117 wrote:
Sat Mar 04, 2023 1:06 am
well it's certainly 9600 baud 8n1 serial, probably bidirectional on that one line. So it's effectively LIN/kline.
Effectively LIN/kline or proper TJA1021 LIN?

Somehow I was not able to sniff with TJA1021 - nothing on RX pin of TJA1021. Yes baud rate was wrong on software side but I would expect something on the scope?
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Re: Honda SEFMJ protocol

Post by AndreyB »

Ohh Link calls it kline
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Re: Honda SEFMJ protocol

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AndreyB wrote:
Sat Mar 04, 2023 1:20 am
Effectively LIN/kline or proper TJA1021 LIN?
They say that LIN is k-line with break and 0x55 sync byte. So here we have k-line not Lin.
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Re: Honda SEFMJ protocol

Post by AndreyB »

Hello CRC8_EBU with 0xFF OutXor

http://www.sunshine2k.de/coding/javascript/crc/crc_js.html
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Re: Honda SEFMJ protocol

Post by puff »

LIN definitely looks different.
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Re: Honda SEFMJ protocol

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Re: Honda SEFMJ protocol

Post by puff »

K-line and Lin, although based on usart, are still different protocols. The image from the scope could be a break frame sent by Lin master (right now playing with it) - it should be followed by sync byte (0x55), and Id byte, followed by data and crc.
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Re: Honda SEFMJ protocol

Post by puff »

L-line is a third one, which is different from Lin
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Re: Honda SEFMJ protocol

Post by AndreyB »

Progress - now with a bench setup!

Now time to improve software a bit :)
2023-03-09_17_28_04_573: EngineState: kline: 0x40
2023-03-09_17_28_04_573: EngineState: kline: 0x7E
2023-03-09_17_28_04_573: EngineState: kline: 0x40
2023-03-09_17_28_04_573: EngineState: kline: 0x7E
2023-03-09_17_28_04_573: EngineState: kline: 0x40
2023-03-09_17_28_04_573: EngineState: kline: 0x7E
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Re: Honda SEFMJ protocol

Post by AndreyB »

thank you @dron_gus for the great idea

Code: Select all

2023-03-10_23_01_06_349: EngineState: kline: got 0x40
2023-03-10_23_01_06_349: EngineState: kline: got 0x00
2023-03-10_23_01_06_349: EngineState: kline: got 0x00
2023-03-10_23_01_06_349: EngineState: kline: got 0x00
2023-03-10_23_01_06_349: EngineState: kline: got 0x7E
2023-03-10_23_01_06_349: EngineState: happy CRC 0x7E
2023-03-10_23_01_06_349: EngineState: kline: got count 0x05
2023-03-10_23_01_06_349: EngineState: kline: got 0x40
2023-03-10_23_01_06_349: EngineState: kline: got 0x00
2023-03-10_23_01_06_349: EngineState: kline: got 0x00
2023-03-10_23_01_06_349: EngineState: kline: got 0x00
2023-03-10_23_01_06_349: EngineState: kline: got 0x7E
2023-03-10_23_01_06_349: EngineState: happy CRC 0x7E
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Re: Honda SEFMJ protocol

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Re: Honda SEFMJ protocol

Post by AndreyB »

Looks like too little data variation to deduct much.

Q packet only happens in the "going to sleep" scenario.

sometimes leading means BCM?: Header 0: packet of length 4. Total 6 payload variations
[0x0 0x1 0x0 0x0 , 0x0 0x40 0x6 0x0 , 0x0 0x40 0x8 0x0 , 0x0 0x40 0x86 0x0 , 0x0 0x40 0xe 0x0 , 0x0 0x50 0x0 0x0 ]

sometimes leading means BCM?: Header 1: packet of length 3. Total 1 payload variations
[0x1 0x0 0x0 ]

unknown: Header 2: packet of length 6. Total 2 payload variations
[0x2 0x0 0x0 0x50 0x0 0x0 , 0x2 0x0 0x10 0x50 0x0 0x0 ]

BCM with A/C: Header 64: packet of length 4. Total 5 payload variations
[0x40 0x0 0x8 0x0 , 0x40 0x40 0x6 0x0 , 0x40 0x40 0x8 0x0 , 0x40 0x40 0x86 0x0 , 0x40 0x40 0xe 0x0 ]

sometimes leading means BCM?: Header 65: packet of length 3. Total 1 payload variations
[0x41 0x0 0x0 ]

rare?: Header 66: packet of length 6. Total 2 payload variations
[0x42 0x0 0x0 0x50 0x0 0x0 , 0x42 0x0 0x10 0x50 0x0 0x0 ]

BCM QUIT: Header 81: packet of length 3. Total 1 payload variations
[0x51 0x0 0x0 ]

rare?: Header 130: packet of length 6. Total 1 payload variations
[0x82 0x0 0x10 0x50 0x0 0x0 ]


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Re: Honda SEFMJ protocol

Post by AndreyB »

I've replayed 0x02 packet and fuse box has noticed!

New logs added into existing zip files https://github.com/rusefi/rusefi_documentation/commit/067ccc76722a82ac7230a8126b086602644c3ae7
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Re: Honda SEFMJ protocol

Post by AndreyB »

AndreyB wrote:
Sun Mar 12, 2023 8:43 am
Looks like too little data variation to deduct much.
Same 0x0 0x10 0x50 0x0 0x0 payload in packets 0x2 0x42 and 0x82 those seem related

0x1 0x0 0x0 from BCM usually gets 0x2 ECU response and 0x41 from BCM usually gets 0x42 response

Same 0x40 0x86 0x0 payload comes in 0x0 and 0x40 packet

Quit 0x51 has same lower "1" nibble.

So it seems to be about nibbles not bytes.

0 lower nibble of first byte BCM status, no response from ECU
1 lower nibble is BCM requesting ECU
2 lower nibble is ECU response
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