Thank you for reaching out to the Wefugee Community!
In general, if you have a residence permit in Germany and a Syrian passport, you are allowed to travel within the European Union (in any case, a travel document is required). Can you explain a bit more in detail, which documents you currently hold? If you have a Syrian passport, why would you need the Ausweisersatz? Do you hold the refugee recognition or the subsidiary protection? If you are recognised as a refugee (first residence permit for three years), you are also able to apply for a refugee passport (the blue one), which would also be a valid travel document. Maybe the discussion in an earlier thread can provide more relevant information: https://www.wefugees.de/804760/ausweis-one-year.
Please get back to us with any further questions or if clarification is needed.
All the best,