P0121

DTC P0121 THROTTLE POSITION CIRCUIT PERFORMANCE PROBLEM





WIRING DIAGRAM

CIRCUIT DESCRIPTION
The throttle position sensor consisting of a contact point (idle switch) and a potentiometer is installed on the throttle body, and detects the throttle valve opening.
The throttle opening in the idle state is detected by means of the contact point which turns ON in that state.
But beyond that, the full opening is detected by the potentiometer as follows.
A 5-volt reference voltage is applied to the sensor from ECM and as its brush moves over the print resistance according to the throttle valve opening, the output voltage varies accordingly.
By monitoring the ON/OFF signal and sensor output voltage, ECM detects the throttle valve opening.
ECM uses the signal from TP sensor as one of the signals to control fuel injector, idle air control valve, ignition timing, EVAP solenoid purge valve and EGR solenoid vacuum valve (if equipped).
Also for 4 A/T model, ECM converts the voltage signal from TP sensor into ON/OFF signal and sends it to transmission control module, where it is used as one of the signals to control the automatic transmission.





DETECTING CONDITION

DTC CONFIRMATION PROCEDURE

NOTE: Check to make sure that following conditions are satisfied when using this DTC CONFIRMATION PROCEDURE.
- Atmospheric pressure : higher than 540 mmHg, 72 kPa (Altitude: lower than 2,790m (9,150 ft)).
- Intake air temp.: -14°C, 6.8°F or higher.

1) Connect scan tool to DLC with ignition switch OFF.
2) Turn ON ignition switch and clear DTC, pending DTC and freeze frame data by using scan tool.
3) Start engine and warm up it completely.
4) Increase vehicle speed till engine speed is reached 3,300-3,700 r/min.
5) Release accelerator pedal, stop vehicle, run engine at idle speed for 5 sec.
6) Check pending DTC and DTC by using scan tool.





TROUBLESHOOTING

NOTE: Troubleshoot DTC P0122 or 123 first when either one was displayed together with DTC P0121.








THROTTLE POSITION SENSOR (TP SENSOR)

Inspection [Using SUZUKI scan tool]
1) Connect SUZUKI scan tool to DLC with ignition switch OFF.
2) Warm up engine and stop it when its temperature has reached normal operating temperature (Check to make sure that they have some clearance between fast idle cam and cam follow lever).
3) Check "THROT POS SENSOR" value displayed on scan tool under following condition.

When throttle is fully close :0.50 ± 0.15 V

When throttle is fully open : 4.0 ± 0.5 V

If measured value is out of above specified range, adjust installation angle of TP sensor.

Adjustments

Also check that "TH ROT POS SENSOR" value varies according to throttle valve opening linearly. If not, it is possible that TP sensor has failed. Replace.

Inspection [Not using SUZUKI scan tool]
1) Remove ECM.
2) Warm up engine and stop it when its temperature has reached normal operating temperature (Check to make sure that they have some clearance between fast idle cam and cam follower lever.).
3) Using voltmeter, check voltage at "E33-17 (E175-25)" terminal under following each condition.

When throttle is fully close : 0.50 ± 0.15 V

When throttle is fully open : 4.0 ± 0.5 V

If measured voltage is out of above specified range, adjust installation angle of TP sensor. Adjustments Also check that voltage varies according to throttle valve opening linearly. If not, it is possible that TP sensor has failed. Replace.

4) Upon completion of checking, install ECM.