Decoding OBDII Comms

[ivanrosales]

For the current, it seems that the amps are 128 reading units apart...
33695 = -6
33567 = -5
33439 = -4
33311 = -3
33183 = -2
33055 = -1
32927 = 0
32799 = 1
32671 = 2
32543 = 3
32415 = 4
32287 = 5
32159 = 6
32031 = 7
31903 = 8
31775 = 9
31647 = 10
31519 = 11
31391 = 12
31263 = 13
31135 = 14
31007 = 15
30879 = 16

Pretty close...

[retepsnikrep]

Thanks for the ideas so far.

Here is some more data for a few functions.

'MPI_MDL Temp C
'$9C $97 = 21C
'$88 $77 = 29C
'$83 $80 = 31C
'$6B $76 = 40C
'$67 $73 = 42C

'DC-DC Converter Temp C
'$97 $22 = 22C
'$7F $41 = 33C
'$77 $41 = 36C
'$76 $6F = 37C
'$72 $6F = 39C

'BAT_MDL Volts
'$91 $10 = 152V
'$95 $00 = 155V
'$98 $0C = 158V
'$9A $05 = 160V
'$9C $00 = 162V
'$9D $00 = 163V
'$9E $00 = 164V

'MPI_MDL Volts
'$97 $7F = 157V
'$98 $B2 = 158V
'$9B $99 = 162V
'$9C $80 = 163V

'MPI_MDL Amps
'$7F $9E = 2A
'$7C $9C = 8A
'$78 $9B = 16A
'$83 $9F = -6A
'$83 $9A = -6 to -8A

TORQUE NM
'$2D $5A = 0 NM
'$3A $5A = 8.4NM
'$41 $5A = 28 to 30 NM
'$2A $5A = -8.4 NM
'$29 $5A = -11.2 NM

Any further help?

[Demon]

The guys above probably already know this stuff. But for those that follow this thread with interest and want to catch up, here's an interesting read:

http://www.obd2crazy.com/techstd.html

(unfortunately the links they posted do not seem to work)

Robert

[retepsnikrep]

Thanks for the ideas so far.

Here is some more refined data for a few functions.

'MPI_MDL Temp C
'$9C = 21C
'$88 = 29C
'$83 = 31C
'$6B = 40C
'$67 = 42C

'DC-DC Converter Temp C
'$97 = 22C
'$7F = 33C
'$77 = 36C
'$76 = 37C
'$72 = 39C

Any ideas on these two?

[retepsnikrep]

Some new data to fox you from an Air Fuel ratio sensor.

The data from the car (left number) converts to the AF (Right number).

255=7.31
224=8.36
192=9.71
160=11.65
128=14.56
96=19.41
64=29.12
32=58.24
16=116.48
8=232.96
4=465.92
2=931.85
1=1863.70

It looks like a typical wideband 02 sensor response with a very steep rise at the end.

I need to establish a formula (if possible) from this data so I can convert the data into the AF.

Now I could capture every value from 0-255 and get exact numbers for each value but that will take a lot of time, and then I would have to do a lookup table for the normal operating range. I could just gather 128 data points from 64 to 192, that encompases the AF range 29.12 - 9.71 which i'm sure covers my cars operating area.

How can I do it without using a look up table? Formula?