DTC P0121: Throttle Position (TP) Sensor System Performance

Start engine and allow to reach normal operating temperature. Turn engine off, leaving ignition on. On models with manual transmission, measure voltage between PCM harness connector "B", terminal No. 17 and ground. On models with automatic transmission, measure voltage between PCM harness connector "D", terminal No. 25 and ground. With throttle fully closed, voltage should be .35-.65 volt. With throttle fully open, voltage should be 3.5-4.5 volts. Ensure voltage varies with throttle position. If voltage is not as specified, adjust TP sensor. See ADJUSTMENTS - 1.8L article. If adjustment cannot be obtained, replace TP sensor. Retest system.