The Electronic Throttle Control(ETC) system consists of the throttle body, Throttle Position Sensor(TPS)1&2 and Accelerator Position Sensor(APS) 1&2. TPS1&2 are sharing the same source voltage and ground. The throttle valve opening is control by throttle motor which is controlled by Engine Control Module(PCM). The opposite position indicator shows inverted signal characteristics. TPS1 output voltage increases smoothly in proportion with the throttle valve opening angle after starting. TPS2 output voltage decreases in inverse proportion with the throttle valve opening angle after starting. TPS provides feedback to the PCM to control the throttle motor in order to control the throttle valve opening angle properly in response to the driving condition.
PCM sets DTC P0123 if the PCM detects signal voltage higher than the possible range of a properly operating TPS1.
Item
Detecting Condition
Possible Cause
DTC Strategy
Short to Battery or Open circuit
Open in ground circuit
Short to battery in signal circuit
Poor connection or damaged harness
Faulty TPS1
Case1
Enable Conditions
Ignition "ON"
Threshold Value
TPS > 4.9V
In idle status
Target throttle angle < 58%
MAF Limphome detected or TPS2 failure detected
TPS1 > 3.0V
Diagnostic Time
0.05 sec.
Mil On Condition
1 Drive Cycles
Limp-Home
Forced limited power mode : When the DTC is set, the PCM reduces engine torque by 25% of normal value.
The PCM uses TPS2 signal to monitor the controlled opening angle of the throttle valve.