K-Line

K-Line on SIMK43 runs at 10400 baud and uses the KWP2000 protocol for diagnostic communication.

Connection points

ECU

- If you have 1.6 or 2.0 without immobilizer installed:

Good news! Your K-Line pins (OBD2/MCC) are connected directly to the K-line pin on the ECU (2.0 - 77)

- If you have 1.6 or 2.0 with immobilizer installed:

Your K-Line pins (OBD2/MCC) are connected to BCM's "Diagnosis" pin (BCM-IM, pin 19). THERE IS NOTHING CONNECTED TO K-LINE PIN AT THE ECU!! (2.0 77). Instead, all K-line stuff is connected to the ECU's W-Line (2.0 - 47)

- If you have 2.7 with or without immobilizer installed:

Your K-Line pins (OBD2/MCC) are connected to BCM's "Diagnosis" pin (BCM-IM, pin 19). Your K/Immo-Line pin at the ECU (C133-1, pin 3) is connected to BCM's "Immo W-line" (BCM-IM, pin 20). 2.7 ECUs don't have a separate K and W line - it's all integrated in one pin, you don't have nothing to worry about.

KWP2000

To start communication, you need to use Fast Init - so bring the K-line down for exactly 25ms, then up for 25ms followed by StartCommunication request. Python example of that using a FTDI cable can be found in GKBus code.

ID of the ECU is 0x11, and as a diagnostic device you should be using ID 0xF1. So an example command and response would look like this:

Diagnostic device: 82 11 F1 27 01 AC (security access request)

ECU response: 83 F1 11 67 02 34 22

Baudrate

By default, SIMK43 uses 10400 baud. On some ECUs (so far testing revealed that <2005 ECUs might not support that), baudrate can be manipulated by additional undocumented parameter of the StartDiagnosticSession service:

0x01: 10400

0x02: 20000

0x03: 40000

0x04: 60000

0x05: 120000

Challenge-response calculation

SIMK43/41 uses a 2 byte seed and 2 byte key for security access. Until a write-up about the algorithm is prepared, you can take a look at it's Python implementation in GKFlasher: https://github.com/Dante383/GKFlasher/blob/15a715b18f2119d697a5ceed00f6383f690c4a23/ecu.py#L42

Input-Output local identifiers

0x10 - check engine light

0x1A - cooling fan relay high

0x1B - cooling fan relay low

0x23 - idle speed actuator

0x24 - cvvt valve

0x50 - adaptive values

Routines by local identifier

0x00 - erase program section

0x01 - erase calibration section

0x02 - verify and mark blocks as ready to execute. Needs to be called after flashing