Ecu fault code 3??

[mrpoody]

Hi. Can anyone tell me what fault code 3 actually means. I have read the code but not really sure what that means in real terms
I have a standard 4l which has been mostly very reliable. Whilst driving to goodwood this weekend it started to run very rough, like on less than 8. Turn off and back on ignition whilst driving cured it for a few miles.
Before the rough running period, it would cut out for a split second and flash up code 3 on my ecu reader then run rough .
It did this about 5 times over 140 miles .
The next day was the same until I pulled off the plug from the ecu and refitted.
Have now travelled about 300 miles since without a single "worryette" .
Over winter I changed the coil, amp, plugs, leads, temp sensor .
Any ideas greatly appreciated.

[davep]

AFAIK The 14CUX ECU has 19 bytes of internal RAM that is battery-backed, normally this means the values held there are not cleared with ignition off or upon ECU code reset. The 'always On' supply for this RAM backup means the unit draws current from the car's battery with ignition off. To verify that the values held in the battery-backed area of RAM are correct a checksum is calculated and used during start up and shut down. If the checksum is not as expected the ECU assumes the battery-backed RAM data has been corrupted or is unreliable, and fault code 03 is set. At the next code reset and with fault code 03 set, the internal RAM is reinitialized, and if the checksum routine is then successful, fault code 03 is reset.

As to the cause, if there's no fault code 02 also being set, it looks like the ECU's internal RAM or its associated circuits are suspect.

HTH