Difference between Physical and Functional Message

I'm updating the VPW page up top.. and I have Physical and Functional messages differentiated. Don't ask me why, I don't know.. which is why I ask the forum. What is the difference?

Also, in this code which I think is wrong cause the source and destinations are funky:
Request current value of PID ($00..$20):
Send: $68,$6A,$F1,$01,$PID
Recv: $48,$6B,$10,$41,$PID,[up to 5 data bytes]

What does the $41 represent in the recieved packet? Is that still a PCM Mode?

I think I need to update that to:
Send: $68,$10,$F1,$01,$PID
Recv: $48,$F1,$10,$41,$PID,[up to 5 data bytes]

From a google search:

For the OBDII mandated diagnostics, requsts are actually made to the functional address 6A, with whatever processor is responsible for this function answering the request. Theoretically many different processors can respond to a single functional request, each contributing their insight as to the information requested.

So I guess the above code is correct.. $6A denotes it as a broadcast functional message coming from $F1 (Scantool)... and $6B is probably funcional message response coming from $10 (PCM)

$6A is Legislated Diagnostics (bit 0 (W bit) = 0 Command)
$6B is Report Legislated Dianostics (bit 0 (W bit) = 1 Status)

The $01 in the send message is "Request Powertrain Diagnostic Data"
The $41 in the receive message is "Report Powertrain Diagnostic Data"

Beerman, so are the $6A and $6B destination addresses. On the VPW page I have the range:
$60-$6F Driver information/Diplays

$6A and $6B does fall under that category correct?

Also, $41 is a regular PCM mode which I can add to the mods list as well correct?

Thanks for the info.

- Keith

$60-$6F Driver information/Diplays are physical nodes.
$6A is a functional address.
I believe the only GM supported functional address is $6A.
Functional address $6A is used for J-1979 messages modes $01 thru $09 and $6B is for responses $41 thru $49

Mode $01 Request Powertrain Diagnostic Data
Response $41 Report Powertrain Diagnostic Data

Mode $02 Request Powertrain Freeze Frame Data
Response $42 Report Powertrain Freeze Frame Data

Mode $03 Request Emission Related Diagnositc Powertrain Trouble Codes
Response $43 Report Emission Related Diagnositc Powertrain Trouble Codes

Mode $04 Clear/Reset Emission-Related Diagnostic Information
Response $44 Emission-Related Diagnostic Information Cleared

Mode $05 Request Oxygen Sensor Monitoring Test Resluts
Response $45 Report Oxygen Sensor Monitoring Test Resluts

Mode $06 Request On-Board Monitoring Test Results for Non-Continuously Monitored Systems
Response $46 Report On-Board Monitoring Test Results for Non-Continuously Monitored Systems

Mode $07 Request On-Board Monitoring Test Results for Continuously Monitored Systems
Response $47 Report On-Board Monitoring Test Results for Continuously Monitored Systems

Mode $08 Request Control of On-Board System, Test, or Component
Response $48 Report Control of On-Board System, Test, or Component

Mode $09 Request Vehicle Information
Response $49 Report Vehicle Information

MODE $09 (J-1979) is not supported by GM use Physically addressed (J-2190) Mode $3C
$3C, $01 (VIN part 1)
$3C, $02 (VIN part 2)
$3C, $03 (VIN part 3)

You will need a copy of J-1979 to find out whats supported and whats not. Search the message board maybe LS1Tools mentioned that it was in one of the EFILive .txt files? I thought it was here http://www.diy-efi.org/gmecm/ecm_info/obd2/ but its not. I'll keep looking for it.

After looking at the GM VPW page I can see where you are getting confused.

Module IDs could be renamed something like Physical Node Addresses

PCM Modes could be split into to sections
J-1979 and J-2190
J-1979 supports modes $01 thru $0F
J-2190 supports modes $10 thru $3F and $80 thru $BF

The request modes will have bit 6 = 0
The response modes will have bit 6 = 1
The response will always be $40 greater than the request mode

Thanks for the info Beerman.. It's still a little confusing to me, but once I get some free time today I'll look into it further.

Thanks again.

- Keith

Beerman, I updated the VPW page, what do you think of the changes?

All PCM Mode Responses could be defined, for example
J2190
MODE $22 Request Diagnostic Data by PID
Response MODE $62 Report Diagnostic Data by PID

You may want to seperate J1979 (functional) from J2190(physical)

and by the way if anyone wondered J1979 Modes $0A thru $0F are reserved

Check out this on J1850http://www.intel.com/design/intarch/papers/j1850_wp.pdf

Thanks again Beerman..

What do you make of:
Mode $7F - General Negative Response

It doesn't fall under either category..

I also seperated them like you suggested, cleans it up nicely.. I can do each response as well.

$7F would be the response from $3F Test Device Present and all other error messages using J2190
$7F is usually followed by another byte to detemine what the actual error code is.

Thanks. I fixed the page.