Why can't I erase DTCs on ABS / SRS / EMS system on Volvo?
Some of the systems fitted to Volvo require particular sequence of operations to erase DTCs. For example some EMS (Engine Management System) require the ignition to be cycled OFF then ON again before they will erase, like wise the DTCs may not set unless the engine has been running for some time.
Some Antilock Braking Systems (ABS) systems will not set a DTC unless the vehicle has been driven above 5Km/h and then checked without the ignition being turned off. Also, some other ABS systems will not turn the warning light off until the car has been driven above 40 Km/h and assuming that no new DTCs have been set.
It should also not be forgotten that if a fault code status is displayed as "Permanent" the fault needs to be rectified before it can be erased. You will know when the fault has been rectified or "gone away" as the status will change to "Intermittent". This is applies to all systems, especially Supplementary Restraint Systems (SRS).
Finally, it has been noted that some variants of the control modules require a specific erase sequence to be performed by the tester which is not happening. These variants are currently being investigated and further improvements will be made within the very near future.