Suzuki Wagon R Manual page 1177

GENERAL INFORMATION AND ENGINE DIAGNOSIS 6-1-85
DTC P0601 INTERNAL CONTROL MODULE MEMORY CHECK SUM ERROR
DTC DETECTING CONDITION POSSIBLE CAUSE
DTC P0601: Data write error (or check sum error) ECM (PCM)
when written into ECM (PCM)
2 driving cycle detection logic, continuous monitoring.
DTC CONFIRMATION PROCEDURE
1) Turn ignition switch OFF.
2) Clear DTC with ignition switch ON and then turn ignition switch OFF.
3) Start engine and run it at idle if possible.
4) Check pending DTC in "ON BOARD TEST" or "PENDING DTC" mode and DTC in "DTC" mode.
INSPECTION
Substitute a known-good ECM (PCM) and recheck.