The Throttle Position Sensor (TPS) is mounted on the throttle body and detects the opening angle of the throttle plate. The TPS has a variable resistor (potentiometer) whose characteristic is the resistance changing according to the throttle angle. During acceleration, the TPS resistance between the reference 5V and the signal terminal decreases and output voltage increases; during deceleration, the TPS resistance increases and TPS output voltage decreases. The PCM supplies a reference 5V to the TPS and the output voltage increases directly with the opening of the throttle valve. The PCM determines operating conditions such as idle (closed throttle), part load, acceleration/deceleration, and wide-open throttle from the TPS. Also The PCM uses the Mass Air Flow Sensor (MAFS) signal along with the TPS signal to adjust fuel injection duration and ignition timing.
The DTC P0121 is set when the intake manifold model filtered reduced area controller is out of range in low or high load.
Item | Detecting Condition | Possible Cause |
DTC Strategy | ● Plausability check | ● Contact resistance in connectors ● Faulty TP Sensor(TPS) |
Enable Conditions | ● No relevant failure ● 10 ≤ Battery voltage ≤ 16 ● Lambda control active | |
Threshold Value | ● Difference between modeled and measured pressure > 280hpa ● Deviation value of fuel trim control > 20% or < -20% | |
Diagnostic Time | ● 200 revolutions | |
MIL On Condition | ● 2 Driving Cycles |
Closed throttle status | Wide open throttle | ||
Throttle opening angle(˚) | 0 ~ 0.5 ˚ | Approx. 86 ˚ | |
Voltage (V) | 0.20 ~ 0.47 V | 4.2 ~ 4.7 V | |
Resistance (㏀) | Terminal 1 & 2 | 0.71 ~ 1.38 ㏀ | 2.7 ㏀ |
Terminal 2 & 3 | 1.6 ~ 2.4 ㏀ | ||
Test Condition | Scan Tool Parameter | Scan Tool Screen | |
TPS VOLTAGE 1 | |||
Normal value with ignition "ON" & engine "OFF" | Accelerator pedal released | 0.20~0.47V | Fig.1 |
Normal value with engine ON & accelerator pedal fully depressed | 4.2~4.7V | - | |
Abnormal value with ignition "ON" & engine "OFF" | Power circuit open | 0.01V | Fig. 2 |
Ground circuit open | 4.99V | Fig. 3 | |
TPS signal circuit open | 4.99V | Fig.4 | |
TPS signal circuit short to ground | Approx. 0V | - | |
TPS signal circuit short to battery | Above 4.99V | - | |
