Thread: OBD initialization problem in OBD cars

According to what I know about ISO-9141 initialization (Volkswagen. K-line communication description), the process must be the following:

1. Tester send a 33h (that is functional addressing) at 5 baud

2. The Vehicle ECU answer with 3 bytes 55h 08h 08h or 55h 94h 94h where 08h or 94h are the key_bytes. This answer is at 10.4 kbps

3. The tester send 1 byte with the key-byte complemented, that is F7h or 6Bh

4. The vehicle closes this initialization phase with a CCh (that is the first 33h complemented).



I am trying to do this initilization phase in an opel Zafira. The first 2 steps are according to the standard.
In this case, the vehicle ECU answer is 55h 08h 08h. Then the tester send the Key-byte complemented F7h, but the problem is that I cannot
detect the last CCh byte that the vehicle should send to close the initialization process.
Why is it happening? Someone can explain it.


I have other problem to initialize an opel Corsa with KWP-fast init protocol. According to the standard that I know, the process must be the following
1. Low pulse + High pulse of 25 mseg each send by the tester.
2. The tester sends: C1h (Byte format), 33h (target address), F1h (source address), 81h (start comm. request service ID) & 66h (checksum).
3. The vehicle ECU must answer with: 83h (byte format), F1h (target address), 10h (source adress), C1h (Start Comm. Response Service ID), xxh (Key_byte#2), 8Fh (key_byte#1) and xxh (checksum).
So, the vehicles answer must be 7 bytes long.
In the Opel Corsa case, it seems that the answer is only 6 bytes long with the following sequence (83h, 7Ch, 14h, E9h, CCh & FFh).
Again, something wrong is happening. Which is the reason?

The initialization phase in Opel cars is different to the standard? Am I reading the answers bad? Do I need to know more about the standards?

Perhaps someone can help me.