Software On ELM Street - OBD2 Software Development

[Tazzi]

Just noticed you E55 (VZ V6) ecu gave you the 7F response... interesting, whereas mine ust spits the answer out immediately without any "wait" message. Hmm.... Might need to implement this "7F" check into the frame check routine, I think Iv added it already to the VIN and serial requests ect.

[Tazzi]

Little bit more research indicates that the message means:
7E8 03 7F 1A 78 00 00 00 00
where:
7E8 = header
03 = length
7F = Negative response
1A = Requested Mode
78 = Positive response forth coming

[VX L67 Getrag]

So what does that mean with positive response fourth coming, do I just need to send the message again until it does respond?

Can I send a similar message to trans controllers?

[Tazzi]

So what does that mean with positive response fourth coming, do I just need to send the message again until it does respond?

Can I send a similar message to trans controllers?

The "positive response fourth coming" means that the proper answer will be sent soon. It happens when the ECU cant respond instantly because it is still accessing the info from its memory. So it means, youll need a modified application that will look for XYZ messages (eg 3 or 4) from the ECU since the response might be 3 lines long instead of only 1! Like the VIN.

Um... Id assume you could do it on the trans controllers? Its a "standardized" request so should work

[Tazzi]

So technically, the ECU did respond back to those messages on those ECUs.. but my software missed the response.. or the ELM may have missed it as well since we didnt tell the ELM how many messages to expect!.

[Tazzi]

Just added in a search for the "7F" responses. So even if the ecu does spit out this response, it should work regardless.
Moving back onto reversing the tech2 LS1 tables today. That *should*, be both the VZ V6 and VY LS1 ecu's completely reversed by the tech2.

[Gareth]

Gee i wish I knew what you are talking about...

me just dumb mechanic

[Tazzi]

Gee i wish I knew what you are talking about...

me just dumb mechanic

Have to have a passion for it to learn these protocols!

[VX L67 Getrag]

Turns out if you send the message a few times it will give us the response we need!

The previous mentioned E77 non SIDI code is 8401 & the previous mentioned E69 SIDI code is 9012!

It took 10 hits of send to get the E69 & only 3hits for the E77

[Tazzi]

Turns out if you send the message a few times it will give us the response we need!

The previous mentioned E77 non SIDI code is 8401 & the previous mentioned E69 SIDI code is 9012!

It took 10 hits of send to get the E69 & only 3hits for the E77

Hahaha, well as long as it worked!
Those ve ecus will be next on the list. I hope that they only require CAN 11bit, and not gmlan for the tech2 to open them up.

But now wesort of have a range for the ECUs.. should be able to detect the ECU type and ensure this marrys up with the vehicle selected