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 (main) outputs voltage which corresponds to the accelerator pedal depression.
  • The engine-ECU checks whether the voltage is within a specified range.

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 for 0.3 seconds.

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-115 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-115 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: C-103 engine-ECU connector

Q. Is the check result normal?

Go to Step 5.

Repair or replace the connector.

STEP 5. Check harness between C-115 (terminal No. 1) accelerator pedal position sensor connector and C-103 (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. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - Precautions Before Service - How to Perform Chassis Number Writing ). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ). After registering the injector identification code, the vehicle equipped with the DPF carries out the forcible DPF regeneration. (Refer to GROUP 17 - Emission Control - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).

STEP 7. Perform resistance measurement at C-115 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: C-103 engine-ECU connector

Q. Is the check result normal?

Go to Step 9.

Repair or replace the connector.

STEP 9. Check harness between C-115 (terminal No. 2) accelerator pedal position sensor connector and C-103 (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: C-103 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-115 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: C-103 engine-ECU connector

Q. Is the check result normal?

Go to Step 13.

Repair or replace the connector.

STEP 13. Check harness between C-115 (terminal No. 3) accelerator pedal position sensor and C-103 (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-115 (terminal No. 1) accelerator pedal position sensor connector and C-103 (terminal No. 149) engine-ECU connector.



  • Check power supply line for damage.

Q. Is the check result normal?

Replace the accelerator pedal position sensor.

Repair the damaged harness wire.

STEP 15. Check harness between C-115 (terminal No. 3) accelerator pedal position sensor connector and C-103 (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.