The Electronic Throttle Control(ETC) system is made of the components 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(ECM).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 ECM to control the throttle motor in order to control the throttle valve opening angle properly in response to the driving condition.
ECM sets DTC P0123 if the ECM detects signal voltage higher than the possible range of a properly operating TPS1.
Item
Detecting Condition
Possible Cause
DTC Strategy
? Voltage range check
? Open in signal or ground circuit
? Short to battery in signal circuit
? Poor connection or damaged harness
? Faulty TPS1
Enable Conditions
Case1
? Ignition "ON"
Case2
? Normal idle status
? TPS setpoint < 20°
? MAF Limphome detected or TPS2 failure detected.
Threshold Value
? TPS1 > 4.9V
? TPS1 at idle >3.0V
Diagnostic Time
? 50 msec.
Limp-Home
? Forced limited power mode : When the DTC is set, the ECM reduces engine torque by 25% of normal value.
? The ECM uses TPS2 signal to monitor the controlled opening angle of the throttle valve.
Test Condition
Scan Tool Parameter
Scan Tool Screen
TPS VOLTAGE 1
TPS VOLTAGE 2
Normal value with ignition "ON" & engine "OFF"
Accelerator pedal released
0.2~0.8V
4.2~4.8V
Fig.1
Normal value with engine ON & accelerator pedal fully depressed
-
Abnormal value with ignition "ON" & engine "OFF"
Power circuit(#2) open
0.01V
0.00V
Ground cicuit(#1) open
4.99V
Fig. 2
TPS1 signal circuit(#4) open
Fig.3
TPS1 signal circuit(#4) short to ground
Approx. 0V
TPS1 signal circuit(#4) short to battery
Above 4.99V
TPS2 signal circuit(#5) open
TPS2 signal circuit(#5) short to ground
TPS2 signal circuit(#5) short to battery