Try erasing the code first, if the light comes back ON you may have to replace the ECM to repair the problem.
There is a factory service bulletin for the 2003 Nissan Altima:
2003 Nissan Altima Factory Service Bulletin OBDII Code P0605
Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
The cost to diagnose the P0605 2003 Nissan Altima Sedan code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.
The Engine Control Module (ECM) continuously monitors its own internal memory status, internal circuits, and output signals transmitted to the throttle actuator. This self-check insures that the ECM is functioning properly. If any malfunction is detected, the ECM sets the P0605 code and illuminates the MIL.
Need more information on how to fix the P0605 2003 Nissan Altima Sedan code? Get Access to Factory Service Manuals
Get the P0605 2003 Nissan Altima Sedan code diagnosed by a professional: Find a repair shop in your area