Tune Detection Flash counters CVN VIN CIN CALID Readyness monitors checks

[steve99]

This information may not be 100% correct but is to the best of my knowledge for BRZ/86/FRS. Its always possible that updates are made to ECU software or hardware allowing additional functions or checks.



OBD –On board diagnostic port also called DLC port. Located near steering wheel under dash.

VIN - Vehicle Identification Number. This is effectively the chassis number and is unique to each vehicle. This will not change when an ECU is reprogrammed.

CIN (CALID) - Calibration Identification Number. This is an identification number stored in each ECU that shows which calibration file is programmed into the ECU example would be ZA1JA01G

CVN - Calibration Verification Number. This is a number which is the result of a calculation carried out based on the calibration data in the ECU. This number will change when the ECU is programmed with anything other than the factory data. This is effectively the result of a checksum algorithm. The ECU calculates this number based on the contents of the flashable areas in the ECU.

The legislation around 2005 also states that these numbers must all be capable of being read by proprietary OBD readers and the numbers may be check during routine emission tests against data which has to be supplied by law from the manufacturers.

The purpose of this legislation is to enable the tester to establish if the ECU has been modified in any way or has been changed from the factory tune/calibration.

The primary purpose of the CVN is so authorities can easily check if the vehicle ECU has the standard factory calibration i.e. tune installed for emissions purposes.

However this also means that the manufacturer also has a very simple method to check if your ECU contents are not standard. Even changing a single setting will cause the CVN to change and then it will no longer match the manufactures list of CVN vs CIN data sheet

Example below

[18:27:03.414] CALID : ZA1JA01D
[18:27:03.429] CVN : ED0690B9
[18:27:03.429] VIN : JF1ZNAA12D2725678

The CVN is basically a "check sum" of the data stored on the ECU. This
is used to determine if the data on the ECU has been corrupted or
changed. If someone is to change the data, like when you tune/flash the ECU with any tune system, the reported CVN will be different than normal/factory number
Any OBD-II Scanner can return the CVN from an ECU as well as CID and VIN
The Subaru Select Monitor tool or the Toyota Techstream software can also read this
data.
Basically, does the Check Sum value match what it should be for that version of ECU software ie the CIN. If not then the ECU contents have been altered ie tuned
When the any form of tune/flash of data occurs other than the standard factory tune is , it changes the CVN so it no longer matches the valid CVN value for the CID from the factory.
This is required because you are altering data in the ECU.
If the CVN is not correct for the new data, the ECU will fail its internal check and not run because it thinks it data is bad.


So, any form of tuning/flashing you are forced to alter the CVN if you want the ECU to run with the new data. That means your not changing the CVN for the sake of changing it, it has to change for the ECU to operate.
If you flash back a completely stock rom/tune i.e. the factory tune with the correct CIN (calid) then the CVN will be returned to factory for that vehicle.


However any tune from any tune system will be detectable if left in ECU.



It is likely possible to modify the ECU firmware to "fake" or disable the CVN/checksum function, but I doubt any tune system manufacturer wants to go down that path as you are deliberatly defrauding emissions laws in most countries. just ask VW how that went :-)


Same for Readyness checks its likely possible but AFAIK no tune systems attempt to fake/disable either readiness or CVN checks.

Readyness Monitors
Additionally, the vehicle stores information known as "readiness indicators" to indicate if the vehicle is ready for an inspection. If too many readiness indicators are "incomplete," the vehicle will fail the inspection because it means that the vehicle has not been operated enough since the on-board memory was last cleared to allow all of the OBD system checks to complete. This can occur if a fault has recently been repaired, or if you have recently had a dead, disconnected, or replaced battery. It does not necessarily mean that anything is wrong with your car - it simply means that the vehicle hasn't had a chance to run all of its self-diagnostics to confirm that everything is okay. The vehicle will need to be driven more before the vehicle can be tested to pass. Vehicle owners who fail Smog Check due to incomplete readiness indicators should drive their vehicle as they normally do for about a week or so to set these readiness indicators to "complete." If the incomplete readiness indicators were most likely not a result of a recently disconnected/replaced vehicle battery, or if the vehicle is not driven regularly, the vehicle owner may wish to seek repair technician help in setting readiness. The technician can access technical information from the vehicle manufacturer and should be able to advise the owner of specific driving patterns needed to set the indicators, or may be able to operate the vehicle (most likely on a dynamometer in the shop) to set the monitors. The technician will have access to a scan tool to determine which monitors have not completed.

You cannot defeat readiness monitor checks by simply disabling the CEL code function in the ECU.

For example simply disabling the P0420 CEL code in the ECU tune just causes the ECU to not register the P0420 code in error log and not to take action it normally would on detection of P0420 ie light the CEL check engine light and to disable Cruise control function.

Readiness checks/monitors require the ecu to evaluate data from varios sensors and process this data for a period of time and get the correct result, this is a totally separate function in ECU then the CEL code disable.

So in this case if you disable P0420 in tune, you will still fail one or more readiness checks related to emissions and catalytic converter function as the ecu will not be receiving the correct data from the 02 sensors required to complete the readiness checks. So the readiness check will never get to "pass"




Flash Counters
Certainly possible but does not appear to be implemented on these cars.


The Subaru or Toyota factory tools to not appear to have a facility to read/display a flash counter.


The factory tools do read out several timers and counters for number of DTC, number of starts since reset. last trip data like temps and various data. but all this data is lost of ECU is reset or powered off or reflashed.






Quote from emissions standards




(4.7) Software Calibration Verification Number

(4.7.1) All 2005 and subsequent model year vehicles shall use an algorithm to calculate a calibration verification number (CVN) that verifies the on-board computer software integrity in diagnostic or emission critical electronically reprogrammable powertrain control units. The CVN shall be made available through the standardized data link connector in accordance with the SAE J1979 specifications. The CVN shall be capable of being used to determine if the emission-related software and/or calibration data are valid and applicable for that vehicle and CAL ID.

(4.7.2) Manufacturers shall request Executive Officer approval of the algorithm used to calculate the CVN. Executive Officer approval of the algorithm shall be based on the complexity of the algorithm and the difficulty in achieving the same CVN with modified calibration values.

(4.7.3) The CVN shall be calculated at least once per driving cycle and stored until the CVN is subsequently updated. Except for immediately after a reprogramming event or a non-volatile memory clear or for the first 30 seconds of engine operation after a volatile memory clear or battery disconnect, the stored value shall be made available through the data link connector to a generic scan tool in accordance with SAE J1979 specifications. The stored CVN value may not be erased when fault memory is erased by a generic scan tool in accordance with SAE J1979 specifications or during normal vehicle shut down (i.e., key off, engine off).

(4.7.4) For purposes of Inspection and Maintenance (I/M) testing, manufacturers shall make the CVN and CAL ID combination information available for all 2005 and subsequent model year vehicles in a standardized electronic format that allows for off-board verification that the CVN is valid and appropriate for a specific vehicle and CAL ID.