DTC P1121: Throttle Position Sensor Signal Lower Than Expected
WARNING: This page is about a different car, the 2003 Acura RSX. However, it is still accessible from the selected car via links, so may be relevant.
Turn ignition switch on. Using scan tool, check throttle position. If throttle position is 12.9 percent, 0.6 volt (K20A2 engine) or 12.6 percent, 0.6 volt (K20A3 engine) or more when throttle is wide open, problem is intermittent. System is functioning properly at this time. If throttle position is not as specified, replace throttle body (TP sensor not available separately).