Secret SERVICE code based on date reset?

[LittleDuceCoupe]

Back in December with my DS3 nearly 2 years old I started getting the "spanner" reminder that the second service would be due soon. All booked in for a couple of weeks later as I needed a car while mine was having the service. Before that, and with loads of miles left counting down by the "spanner", a bright SERVICE warning came up on the dashboard. So I had the service done and the service mileage countdown had been reset by the garage. A month later on 5th Jan the bright SERVICE light came up on the dashboard again but this time along with the engine management light. Called my breakdown club who retrieved and cleared the fault code P13A9. The fault code did not come back so they said go for a long run to see if it came back. I relayed this information to my Citroen service garage who said to just keep an eye on it as they would have difficulty in replicating the fault condition.
So anyway, exactly a month later (today), up comes the SERVICE warning and engine light again!
So my question is, after the service is there something else that the garage have to reset apart from the mileage countdown. Is there something in the "brain" of the car that relates service intervals based on date?
And what is code P13A9?
Please help.

Dave. :confused:

[Shiro]

P13XX means you have problems with the ignition. I would go to the garage and let them see what's going on with the engine.

[cyclone]

What he said + Don't reset it this time so the stored code will be there for the garage to see. Also the SERVICE light comes on for some actual problems other than your periodic service. So really nothing to do with the service you had done, Just coincidence.

[DaveB]

According to the Owner's Handbook "SERVICE" lights to indicate a fault for which there is no specific warning lamp & should be accompanied by a message on the screen indicating the fault.

[LittleDuceCoupe]

Well it has just happened again! Bleep, SERVICE light and message on the display saying "Engine Fault - Repair Needed" and the engine management light on. As this was over the weekend I have continued to use the car as it is all running OK. Just a bit distracting to have the EML on the dash. After a couple of journeys the SERVICE light did not appear anymore but I was still getting the warning message and EML light on. So Monday morning tried to call BOLLINGMORES but no reply. So as their service manager had previously said just bring it along with the light on I set off. I still got the beep and the warning message on the display but now the EML light was no longer on? Drove to BOLLINGMORES to find that their gates were all chained up. Asked around and was informed that they had suddenly gone into liquidation. Drove home with no warning beep, message or EML on?
How can this have cleared itself? Will any fault code still be stored?
Does anyone know a Citroen main dealer around North Surrey?