KWP 2000 (ISO 15765-4) bus protocol question

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Recently I tried to install my product on Peuzeot(406 or something
similar). There was
KWP 2000 bus. I tried to get the speed value from the bus by sending
the following string
0xc2 0x33 0xf1 0x01 0x0d 0xf4.
On responce I received two answers from 2 different ECUs:
1) 0x83 0xf1 0x10 0x7f 0x01 0x12 0x16
1) 0x83 0xf1 0xa4 0x41 0x0d 0x00 0x66

The first ECU sent me NACK
(This response code indicates that the requested action will not be
taken because the server (ECU) does not support the arguments of the
request message or the format of the argument bytes do not match the
prescribed format for the specified service.)

My question is: if there was something wrong with the arguments of the
request message, the second ECU also should not understand the
request, bit it did !
And the second question is: why the first ECU did send the negative
answer. If you look at the j1979 PDF you will find there that "If an
ECU does not support any of the PIDs requested it is not allowed to
send a negative response message".

Best regards,
Eli.

Re: KWP 2000 (ISO 15765-4) bus protocol question
this command might be respond  NACK because you ahave to pass first a
security access!

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