Code No. P2122: Accelerator Pedal Position Sensor (main) Circuit Low Input


OPERATION



  • A power voltage of 5 V is applied to the accelerator pedal position sensor (terminal No. 1) from the engine-ECU (terminal No. 149).
  • The power voltage is earthed to the engine-ECU (terminal No. 151) from the accelerator pedal position sensor (terminal No. 2).
  • The sensor signal is inputted to the engine-ECU (terminal No. 150) from the accelerator pedal position sensor output terminal (terminal No. 3).

FUNCTION



  • The accelerator pedal position sensor converts the opening degree of the accelerator pedal into the voltage signal to input it to the engine ECU.
  • The engine ECU uses this signal to determine the amount of basic fuel injection.

TROUBLE JUDGMENT


Check Conditions
  • Ignition switch is in "ON" position
  • Accelerator pedal position sensor (sub) is normal
Judgment Criterion
  • Accelerator pedal position sensor (main) output voltage is lower than 0.2 V.

FAIL-SAFE AND BACKUP FUNCTION



  • The amount of depression of the accelerator pedal is detected, using the accelerator pedal position sensor (sub) signal, which is calculated by taking half of the normal value.

PROBABLE CAUSES



  • Failed accelerator pedal position sensor
  • Open/short circuit or harness damage in accelerator pedal 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 9: Accelerator pedal 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: C-23 accelerator pedal position sensor connector

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

STEP 3. Perform voltage measurement at C-23 accelerator pedal position sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 1 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-10 engine-ECU connector

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

STEP 5. Check harness between C-23 (terminal No. 1) accelerator pedal position sensor connector and B-10 (terminal No. 149) 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 9: Accelerator pedal 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. Perform resistance measurement at C-23 accelerator pedal position sensor connector.

  • Disconnect connector, and measure at harness side.
  • Resistance between terminal No. 2 and earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?
Go to Step 10 .
Go to Step 8 .

STEP 8. Connector check: B-10 engine-ECU connector

Q. Is the check result normal?

    Go to Step 9 .
Repair or replace the connector.

STEP 9. Check harness between C-23 (terminal No. 2) accelerator pedal position sensor connector and B-10 (terminal No. 151) engine-ECU connector.

  • Check earthing line for damage.

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

STEP 10. Connector check: B-10 engine-ECU connector

Q. Is the check result normal?
Go to Step 11 .
Repair or replace the connector.

STEP 11. Perform voltage measurement at C-23 accelerator pedal position sensor connector.

  • Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
  • Ignition switch: ON
  • Voltage between terminal No. 3 and earth.
OK: 0.7 - 1.3 V

Q. Is the check result normal?
Go to Step 15 .
Go to Step 12 .

STEP 12. Connector check: B-10 engine-ECU connector.

Q. Is the check result normal?
Go to Step 13 .
Repair or replace the connector.

STEP 13. Check harness between C-23 (terminal No. 3) accelerator pedal position sensor and B-10 (terminal No. 150) engine-ECU connector.

  • Check output line for short circuit.

Q. Is the check result normal?
Go to Step 14 .
Repair the damaged harness wire.

STEP 14. Check harness between C-23 (terminal No. 1) accelerator pedal position sensor connector and B-10 (terminal No. 149) engine-ECU connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Replace the accelerator pedal assembly.
Repair the damaged harness wire.

STEP 15. Check harness between C-23 (terminal No. 3) accelerator pedal position sensor connector and B-10 (terminal No. 150) engine-ECU connector.

  • Check output line for open circuit and damage.

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