Code No. P0122: Throttle Position Sensor (Main) Circuit Low Input








OPERATION



  • A power voltage of 5 V is applied to the electronic-controlled throttle valve (terminal No. 5) from the engine-ECU (terminal No. 12).
  • The power voltage is earthed to the engine-ECU (terminal No. 13) from the electronic-controlled throttle valve (terminal No. 3).
  • The sensor signal is inputted to the engine-ECU (terminal No. 10) from the electronic-controlled throttle valve output terminal (terminal No. 4).

FUNCTION



  • The throttle position sensor converts the throttle valve position into voltage and inputs it into the engine-ECU.
  • The engine-ECU controls the throttle valve position.

TROUBLE JUDGMENT


Check Condition
  • Ignition switch is "ON" position.
Judgement Criterion
  • Throttle position sensor (main) output voltage should be 0.2 V or less.

PROBABLE CAUSES



  • Failed throttle position sensor (main)
  • Open/short circuit or harness damage in throttle position sensor circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 13: Throttle position sensor (main)

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Go to Step 2 .

STEP 2. Connector check: B-20 electronic-controlled throttle valve connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Perform voltage measurement at B-20 electronic-controlled throttle valve connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 5 and earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?
Go to Step 7 .
Go to Step 4 .

STEP 4. Connector check: B-29 engine-ECU connector

Q. Is the check result normal?
Go to Step 5 .
Repair or replace the connector.

STEP 5. Check harness between B-20 (terminal No. 5) electronic-controlled throttle valve connector and B-29 (terminal No. 12) engine-ECU connector.

  • Check power supply line for open/short circuit.

Q. Is the check result normal?
Go to Step 6 .
Repair the damaged harness wire.

STEP 6. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 13: Throttle position sensor (main)

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Replace the engine-ECU.

STEP 7. Connector check: B-29 engine-ECU connector

Q. Is the check result normal?
Go to Step 8 .
Repair or replace the connector.

STEP 8. Check harness between B-20 (terminal No. 5) electronic-controlled throttle valve connector and B-29 (terminal No. 12) engine-ECU connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 9 .
Repair the damaged harness wire.

STEP 9. Check harness between B-20 (terminal No. 4) electronic-controlled throttle valve connector and B-29 (terminal No. 10) engine-ECU connector.

  • Check output line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 10 .
Repair the damaged harness wire.

STEP 10. Replace the electronic-controlled throttle valve

  • After replacing the electronic-controlled throttle valve, re-check the trouble symptoms.

Q. Is the check result normal?
Check end.
Replace the engine-ECU.