Odp: 5 baud ECM?

[Marek]

Hi
> Sounds like the Bosch protocol to me, and what a pain it is.

This's ISO - 9141-1  protocol but elaborated by Bosch.This protocol is used
generally on Bosch ECU.

> You wake the
> unit up with a 5 baud initial handshake word,

For EFI initializing is done by sending  adress 0x10 .After that the ECU
should response with six bytes .Where first must be 0x55 ,the next two bytes
are called keyword1,keyword2(these bytes describe the ECu family),the byte
4th C1 and 5th C2 (these bytes describe differences in the family) and last
one is CHK (check sum) .The tester must send to ECU keyword2 negated (!K2).

> then talk to it at 9600 baud.

After initializing the ECU and tester  prepare  to communicate with baud
rate 4800.The communication is block-by-block with the different lenght
.Every block in the header has got cell where is stored the block lenght
.There're three types of ISO-9141 communication : ISO5 (one line
bidirectional -K line),ISO8 (one line bidirectional -K line,one
unidirectional to ECU- L line - serves only for initializing ),ISO4 (two
lines unidirectional -K line to tester,L line to ECU) .This protocol is
possibily straight implemented to use with  PC via straight interface
without using special chips .But this communication protocol is fairly
complicated  !!!!

Cheers
Marek

> Used on most European GM (Opel/Vauxhall) cars, and not only for ECM's -
> Airbag, ABS, AutoTrans, Alarms, the list is endless.
>
> I haven't found anyone who knows how it works, or a cheap DIY style PC
scan
> tool. Only thing that works is a real Tech1. I'm glad my car is one of the
> few with a P4 in it.
>
> Cheers,
> Malcolm Robb, LC 0112G
>
> -----Original Message-----
> From: Peter Gargano [SMTP:peter at techedge.com.au]
> Sent: Monday, July 16, 2001 1:21 PM
> To: gmecm at diy-efi.org
> Subject: 5 baud ECM?
>
> Anyone know anything about the five baud GM ALDL protocol?
> I've heard that some Opels use it for initial handshake. Is
> this with a GM, or a Bosch ECM?
>
> TIA, Peter.
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