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 opening angle.

TROUBLE JUDGMENT


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

FAIL-SAFE AND BACKUP FUNCTION



  • Throttle opening degree is restricted.
  • Throttle opening degree position is in default position if throttle position sensor (sub) fails.

PROBABLE CAUSES



  • Failed throttle position sensor (main)
  • 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

  • Data list reference table (Refer to ).

  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-12 electronic-controlled throttle valve connector and B-26 engine-ECU connector

Q. Are the check results normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Check harness between B-12 (terminal No. 5) electronic-controlled throttle valve connector and B-26 (terminal No. 12) engine-ECU connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 4 .
Repair the damaged harness wire.

STEP 4. Check harness between B-12 (terminal No. 4) electronic-controlled throttle valve connector and B-26 (terminal No. 10) engine-ECU connector.

  • Check output line for short circuit.

Q. Is the check result normal?
Go to Step 5 .
Repair the damaged harness wire.

STEP 5. M.U.T.-III data list

  • Data list reference table (Refer to ).

  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 6 .

STEP 6. Replace the electronic-controlled throttle valve

  • After replacing the electronic-controlled throttle valve, reconfirm whether the diagnosis code is set.

Q. Is the diagnosis code set?
Replace the engine-ECU.
Check end.