Protocol
K-Line and L-Line (ISO 9141-2 / ISO 14230)
The K-Line is a single-wire serial line on pin 7 of the OBD socket, used to diagnose cars before CAN; ISO 9141-2 and ISO 14230 (KWP2000) define how it's used. The L-Line, on pin 15, only helps wake the ECU up when communication starts.
Reviewed by Daniel Morales, founder of Reprorace SL, on
Key facts at a glance
| Protocol | Standard | J1962 pins | Speed or link | ECO-LITE | ECO-LITE TOOL | ECOPRO Gen4 |
|---|---|---|---|---|---|---|
| K-Line | ISO 9141-2 · ISO 14230 (KWP2000) | 7 | 5-baud or fast initialization | Yes | Reproduces the vehicle's | Yes |
| L-Line | ISO 9141-2 | 15 | Only to start communication | In validation | Not yet | Not stated |
Data from the device catalog and the standards cited. The devices are in pre-production: figures may be adjusted after the first units have been validated.
When you need it
- Cars with diagnostic protocols from 2005 onwards that still use K-Line on some ECU
- ECUs that need a 5-baud initialization before they respond
- Body or comfort systems still on K-Line even though the engine runs over CAN
Which Diaglana device covers it, and its limits
- ECO-LITE
- K-Line on pin 7, with 5-baud and fast initialization; it monitors the line so it never locks up the car's bus. The L-Line on pin 15 is in validation.
- ECO-LITE TOOL
- Reproduces the remote car's K-Line for your tool. Not the L-Line yet.
- ECOPRO Gen4
- K-Line and J1850. In development.
Frequently asked questions
What's the difference between ISO 9141-2 and ISO 14230?
Both use the K-Line. ISO 9141-2 is the older emissions protocol; ISO 14230, also known as KWP2000, adds fast initialization and the diagnostic services many ECUs used before UDS.
What is the L-Line for?
Only for starting communication on some cars: the ECU listens for the address on K and L at the same time, then replies on K alone.
What is 5-baud initialization?
A slow way of waking the ECU: the tester sends its address bit by bit at 5 baud and the ECU replies with its key bytes. Communication then continues at normal speed.
Want to try it in your workshop?
Check the device page for the full specifications, or buy in the shop at the final price.