Couldnt really find a section for this..

[festy]

Bear with me here, I've never seen one of these trip computers...

I don't think the first 8 bytes relate to the odometer in any way, so assume they're personality and/or function configuration settings.
What do these trip computers actually do? You mentioned cruise control - does it remember your last set speed?
Are there any other parameters that can be set with the trip computer, like overspeed alarm etc?

[88GreenVN]

Bear with me here, I've never seen one of these trip computers...

I don't think the first 8 bytes relate to the odometer in any way, so assume they're personality and/or function configuration settings.
What do these trip computers actually do? You mentioned cruise control - does it remember your last set speed?
Are there any other parameters that can be set with the trip computer, like overspeed alarm etc?

I think your correct on the first 8 bytes not relating to the ODO as I could set the odo and stilll get a fail.

There is 4 settings that can be changed by the user to "calibrate" the trip computer to each individual car.

Distance - factory default 625
Fuel Flow - Factory default 625
Fuel remaing in the tank
Over speed alert


In Diag mode you can get the following:
A digital speedo when the car is started and driven in Diag mode.
Volts from the battery
Volts from the fuel sender unit
Button test screen (for the control button function)
Fuel flow in Lts per hour

I think I'll go change some of the default settings and see if that changes the first 8 bytes - I'll use 1 of the obove odo .bin files.

[88GreenVN]

Update on testing the first 8 bytes.

Distance, fuel flow and tank size are the first 3 bytes. I just changed the 625 to 626. So now to work backwards to see what the calcs are for this group of numbers.

So back to shed to play some more and see what other changes I can make.

[88GreenVN]

Changing the setting for the fuel tank from 60 to 80 Lts.


01 01 D9 26 = Default 60lt
01 01 39 C6 = 80lt tank selected.

Changing the distance to 626 (+1) (Fuel Flow 625 default)
81 01 59 26

Changing Fuel Flow to 626 (leaving distance at 625 default)
01 81 59 26

So the thrid byte of data stays 59 if either 1 of the 2 default 625 is changed by 1. But is affected by the fuel tank size selection also....

The overspeed setting is lost when the trip computer is disconnected. So far nothing has changed the second half of the first 8 bytes.

[The1]

fuel tank size is the switch on the back though isn't it? So your saying that writes to the chip when changing the switch?

[festy]

The 60/80l bytes might be a checksum pair, but the last examples you posted don't add up...
The bytes might make more sense after endian conversion?

[88GreenVN]

fuel tank size is the switch on the back though isn't it? So your saying that writes to the chip when changing the switch?

Yes if you change the switch on the trip it changes the D9 26 to 39 C6.

I've just gone and changed the 2 default 625's to 626 and the D9 stayed 59 - I'll go repeat this now to see if I got that right.

I put the trip into Ign on mode and then press set button for 3 secs. This brings up the settings stored in the trip computer. The 80 setting has a default 90.0 and the 60 setting went to -10. Changing the amount remaining in the tank calibration by .1 (89.9 stored in the trip computer) should give a new number .... back to shed.

[88GreenVN]

The 60/80l bytes might be a checksum pair, but the last examples you posted don't add up...
The bytes might make more sense after endian conversion?

That was a typo on the 08 - shoud have been 01 (default 625)

[88GreenVN]

With the tank size set to 80 I changed the calibration by 1 - 3 times

+1 = 01 01 59 A6
+2 = 01 01 99 66
+3 = 01 01 19 E6

[festy]

Can you spot the 5-6-7 progression there?
It is checksummed too.