Older European cars on the K-line
Many European cars from the 2000s talk OBD2 over the K-line, an older and slower connection than CAN. They work with Read My Car, but connecting takes longer: often up to 30 seconds, and up to about two minutes if the adapter can’t find the protocol by itself.
Updated
Which cars
As a rule, EOBD is required on petrol cars from 2001 and diesels from 2004 in the EU. Many of the earlier EOBD cars, such as older Peugeots, Citroëns, cars of the VW group, Renaults and Fiats, use the K-line rather than CAN. Newer cars mostly use CAN.
Read My Car shows the protocol your car uses under Vehicle.
The protocols
- ISO 9141-2
- K-line at 10.4 kbaud. Needs a slow wake-up of 2 to 3 seconds before the car answers.
- ISO 14230-4 (KWP2000)
- The same wire, with a slow wake-up or a faster one.
- ISO 15765-4 (CAN)
- The fast network on most newer cars. No wake-up needed.
Why connecting is slow
When the adapter doesn’t know the protocol, it tries them one after another, and each K-line try needs its own wake-up. That adds up. The adapter’s own search gets up to 30 seconds; if it fails, Read My Car tries each protocol in turn, which can take up to about two minutes in all. The connect screen says when it takes longer than usual. Keep the ignition on while it searches.
Once connected, the K-line is slower too: live data updates less often than on a CAN car.
Clones that struggle
Some clone adapters fail to find the protocol by themselves on K-line cars, although they work once told which one to use. When the automatic search fails, Read My Car tries each protocol in turn, the ones most likely for European cars first.
You can also choose the protocol in Settings, but only if automatic fails. If the car then doesn’t answer, set it back to Automatic.
What’s different on older engine computers
- One reading per request, so live data with several readings updates slowly.
- No permanent codes: older engine computers usually don’t support them, so none are listed.
- Some don’t confirm a clear. Read My Car always reads the codes again to check.
- The VIN may come in several parts, and some cars don’t report it at all.
Try the demo Peugeot
The 2004 Peugeot 307 HDi in the app is a simulated K-line diesel on KWP2000, slower to connect like the real thing. It has stored codes, a pending code, a freeze frame and an EGR self-test that isn’t complete, and no permanent codes.
If it won’t connect
- Switch the ignition on. The engine can stay off.
- Wait: up to 30 seconds is common, and up to about two minutes if Read My Car has to try each protocol in turn. Keep the ignition on while it searches.
- Push the adapter firmly into the socket.
- Check that the protocol in Settings is Automatic.
- Turn the ignition off and on again, unplug the adapter for 5 seconds, and try again.
Questions
Why does my car take so long to connect?
K-line cars need a wake-up before they answer, and the adapter may try several protocols first. Up to 30 seconds is common; if the adapter’s own search fails and Read My Car tries each protocol in turn, it can take up to about two minutes.
Is my adapter faulty if the automatic search fails?
Not necessarily. Some clones struggle with the automatic search on K-line cars but work once the protocol is chosen. Read My Car then tries each protocol in turn.
Why doesn’t my older car show permanent codes?
Older engine computers usually don’t support them. Stored and pending codes are read as usual.