DTC is made up of 5 digits.
Example: P0101
1st digit
B-Body
C-Chassis,
P-Powertrain
U-Network
2nd digit
0 Generic
1 Manufacturer specific
3rd digit
1 Air & Fuel Metering
2 Air & Fuel Metering (Injector Circuit)
3 Ignition System or Misfire
4 Auxiliary Emissions Controls
5 Vehicle Speed Controls And Idle Control System
6 Computer Output Circuit
7 Transmission
8 Transmission
4th & 5th digit Identifies what section of the system is malfunctioning
So, P-1955
"P" is powertrain
"1" is Manufacturer specific
"9" is a mystery.
I know that does not help you but it breaks down some of it..
Michael