P0120

DESCRIPTION

NOTE: If DTC P0120 is displayed with DTC P0510, first perform the trouble diagnosis for DTC P0510.

COMPONENT DESCRIPTION
The throttle position sensor responds to the accelerator pedal movement. This sensor is a kind of potentiometer which transforms the throttle position into output voltage, and emits the voltage signal to the ECM. In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM.

Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor. This sensor controls engine operation such as fuel cut. On the other hand, the "Wide open and closed throttle position switch", which is built into the throttle position sensor unit, is not used for engine control.

Consult-II Reference Value In Data Monitor Mode:

ON BOARD DIAGNOSIS LOGIC
Malfunction is detected when
(Malfunction A) an excessively low or high voltage from the sensor is sent to ECM,
(Malfunction B) a high voltage from the sensor is sent to ECM under light load driving conditions,
(Malfunction C) a low voltage from the sensor is sent to ECM under heavy load driving conditions.

FAIL-SAFE MODE
When the malfunction A is detected, the ECM enters fail-safe mode and the MIL lights up.

Possible Cause

MALFUNCTION A
- Harness or connectors
(The throttle position sensor circuit is open or shorted.)
- Throttle position sensor

MALFUNCTION B
- Harness or connectors
(The throttle position sensor circuit is open or shorted.)
- Throttle position sensor
- Fuel injector
- Crankshaft position sensor (REF)
- Crankshaft position sensor (POS)
- Mass air flow sensor

MALFUNCTION C
- Harness or connectors
(The throttle position sensor circuit is open or shorted.)
- Intake air leaks
- Throttle position sensor

DTC Confirmation Procedure

NOTE:
- Perform "PROCEDURE FOR MALFUNCTION A" first. If the 1st trip DTC cannot be confirmed, perform "PROCEDURE FOR MALFUNCTION B".
If there is no problem on "PROCEDURE FOR MALFUNCTION B", perform "PROCEDURE FOR MALFUNCTION C".
- If "DTC Confirmation Procedure" has been previously conducted, always turn ignition switch "OFF" and wait at least 10 seconds before conducting the next test.

PROCEDURE FOR MALFUNCTION A

CAUTION: Always drive vehicle at a safe speed.

TESTING CONDITION:
- Before performing the following procedure, confirm that battery voltage is more than 10 V at idle.
- This test may be conducted with the drive wheels lifted in the shop or by driving the vehicle. If a road test is expected to be easier, it is unnecessary to lift the vehicle.

WITH CONSULT-II
1. Turn ignition switch "ON" and select "DATA MONITOR" mode with CONSULT-II.

2. Start engine and maintain the following conditions for at least 5 consecutive seconds.
3. If 1st trip DTC is detected, go to "Diagnostic Procedure" at the end of the article.

WITH GST
Follow the procedure "With CONSULT-II" above.

PROCEDURE FOR MALFUNCTION B

WITH CONSULT-II
1. Turn ignition switch "ON".
2. Select "DATA MONITOR" mode with CONSULT-II.

3. Start engine and let it idle for at least 10 seconds.
If idle speed is over 1,000 rpm, maintain the following conditions for at least 10 seconds to keep engine speed below 1,000 rpm.
4. If 1st trip DTC is detected, go to "Diagnostic Procedure" at the end of the article.

WITH GST
Follow the procedure "With CONSULT-II" above.

PROCEDURE FOR MALFUNCTION C

CAUTION: Always drive vehicle at a safe speed.

WITH CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch "OFF" and wait at least 10 seconds.
3. Turn ignition switch "ON".
4. Select "MANU TRIG" in "DATA MONITOR" mode with CONSULT-II.
5. Select "THRTL POS SEN" and "ABSOL TH.P/S" in "DATA MONITOR" mode with CONSULT-II.

6. Press RECORD on CONSULT-II SCREEN at the same time accelerator pedal is depressed.

7. Print out the recorded graph and check the following:
- The voltage rise is linear in response to accelerator pedal depression.
- The voltage when accelerator pedal is fully depressed is approximately 4 V.
If NG, go to "Diagnostic Procedure" at the end of the article.
If OK, go to following step.

8. Select "AUTO TRIG" in "DATA MONITOR" mode with CONSULT-II.

9. Maintain the following conditions for at least 10 consecutive seconds.
10. If 1st trip DTC is detected, go to "Diagnostic Procedure" at the end of the article.

WITH GST
1. Start engine and warm it up to normal operating temperature.

2. Maintain the following conditions for at least 10 consecutive seconds.
3. Select "MODE 7" with GST.
4. If 1st trip DTC is detected, go to "Diagnostic Procedure" at the end of the article.