Error when running P11D process for Car

Summary: Error when running P11D process

Content (required): We are testing P11D reporting for 2021/22. The calculation cards are populated with the mandatory details but we are receiving an error :

Flow Instance Name,Error Level,Action ID,Employee Name,Person Number,Payroll Relationship Number,Issue Raised

RS P11D v22,Payroll Relationship Action,236615536,PXXXX,XXXX,XXXX-1,"The benefit Cars and Car Fuel with unique reference Y100XXX has Cars cash equivalent entered where fuel is provided. You must provide a cash equivalent for fuel."

Any ideas on what this error is referring to?

Version (include the version you are using, if applicable):