Warning and Shut-down Scenario: Notes

The SCR system is relevant to the vehicle complying with the exhaust emission regulations - it is a prerequisite for EPA approval.

If the system fails, the approval will be invalidated and the vehicle must no longer be operated. A very plausible case leading to the system failure is that the urea-water solution runs out.

Vehicle operation is no longer permitted without the urea-water solution, therefore, the engine will no longer start. To ensure the driver is not caught out, a warning and shut-down scenario is provided that begins at a sufficiently long time before the vehicle actually shuts down so that the driver can either conveniently top up the urea-water solution himself or have it topped up.