The Throttle Position Sensors (TPS) are used to inform the control unit about the position of the throttle, whether it is fully closed or fully open. These sensors are located in a single housing at the end of the throttle assembly. If either switch fails, the control unit will rely on air meter signals to calculate idle and full load control, and a fault code will be stored in memory. To test the TPS, a BMW service tester, OBD I blink code, or a suitable Data Scan Tool (DST) can be used to check for faults or read component values. If this equipment is not available, a continuity tester or ohmmeter can be used. For 1989-95 models with M20 or S14 engines, there should be continuity between specific terminals when the throttle is closed or fully open. The switch can be adjusted by loosening the screws on the housing. For M42 or M50 engines, the potentiometer should receive 5 volts with the ignition switch ON, and specific resistance values should be measured between terminals. The resistance should change smoothly as the throttle is moved. For 1996-98 models, the TPS is mounted on the side of the throttle housing and cannot be adjusted. The voltage signal and resistance values should be checked using a digital voltmeter and ohmmeter. If the sensor has failed, it must be replaced. To remove and install the TPS, the ignition switch should be turned off, the connector should be unplugged, and the switch should be removed using screws. On M20 and S14 engines, the switch must be adjusted for continuity between specific terminals when the throttle is closed or fully open. The switch can be adjusted by loosening the screws on the housing.