Error Codes, P0171 and P0374

I used the OBD II / EOBD CODE READER and found the following code (four error codes)
P0171 System too lean Bank 1 (Generic o)
P0374 Timing Reference Hig n Resolution Signal A No Pulses (Generic o)
P0171 System too lean Bank 1 (Gen Pd o)
P0374 Timing Reference Hig n Resolution Signal A No Pulses (Gen Pd o)
Freeze Frame:
DTCFRZF P0171
Fuel sys 1 CL
Fuel sys 2 --
Load_PCT (%) 75.29
ECT( ‘C) 78.00
SHRTFT1 (%) 0.00
LONGFT1 (%) 25.00
SHRTFT2 (%) 0.00
LONGFT2 (%) 25.00
MAP (kPa) 47.00
RPM(rpm) 705.50
VSS(km/h) 0.00
SPARKADV 4.5
IAT(‘C) 00.00
MAF(g/s) 6.28
TP(%) 18.43
I do not feel anything while driving (I do not have much knowledge about vehicles), It accelerates well and goes easily to forty miles per hour when given the acceleration (I have not tried beyond forty miles per hour in order to avoid any damage. I bought it recently and want to repair it before use) the odometer reads about 200,000 miles. I showed to a local mechanic he said the gear is either in second or third (limp mode) after a short test drive, which made me little worried. What can be the possible reasons of this errors and what should I do to make it a smooth running vehicle?