DTC P0121 - Throttle Position (TP) Sensor Circuit Range

Install scan tool. Start engine and check if DTC P0121 is present. If DTC is present, go to next step. If DTC is not present, problem is intermittent.
Check continuity of circuit between TP sensor and MAF sensor. See appropriate wiring diagram in WIRING DIAGRAMS section. Repair circuit as necessary. If circuit is okay, go to next step.
Turn ignition off. Disconnect TP sensor harness connector. Connect an analog type ohmmeter between TP sensor terminals No. 1 and 3. Move throttle from idle to wide-open position. Ohmmeter needle should sweep smoothly, in proportion to throttle opening. If movement is not smooth, replace TP sensor. If movement is smooth, go to next step.
Check MAF sensor. For further diagnosis, see related DTC or SYSTEM/COMPONENT TESTS article. Replace MAF sensor as necessary. If MAF sensor is okay, go to next step.
Clear DTC. See CLEARING DTC(S) . Retest system. If DTC resets, replace ECM.