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 connector terminal from the engine-ECU connector terminal APS5.
  • The power voltage is earthed to the engine-ECU connector terminal APSE from the accelerator pedal position sensor connector terminal.
  • The sensor signal is inputted to the engine-ECU connector terminal APSM from the accelerator pedal position sensor output terminal.

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. Perform voltage measurement at accelerator pedal position sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal engine-ECU APS5 line and body earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?
Go to Step 5.
Go to Step 3.

STEP 3. Check harness between accelerator pedal position sensor connector terminal and engine-ECU connector terminal APS5.

  • Check power supply line for open/short circuit.

Q. Is the check result normal?
Go to Step 4.
Repair or replace the connector, or repair the damaged harness wire.

STEP 4. 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 5. Perform resistance measurement at accelerator pedal position sensor connector.

  • Disconnect connector, and measure at harness side.
  • Resistance between terminal engine-ECU APSE line and body earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?
Go to Step 7.
Go to Step 6.

STEP 6. Check harness between accelerator pedal position sensor connector terminal and engine-ECU connector terminal APSE.

  • Check earthing line for damage.

Q. Is the check result normal?
Go to Step 4.
Repair or replace the connector, or repair the damaged harness wire.

STEP 7. Perform voltage measurement at 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 engine-ECU APSM line and body earth.
OK: 0.7 - 1.3 V

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

STEP 8. Check harness between accelerator pedal position sensor connector terminal and engine-ECU connector terminal APSM.

  • Check output line for short circuit.

Q. Is the check result normal?
Go to Step 9.
Repair or replace the connector, or repair the damaged harness wire.

STEP 9. Check harness between accelerator pedal position sensor connector terminal and engine-ECU connector terminal APS5.

  • Check power supply line for damage.

Q. Is the check result normal?
Replace the accelerator pedal assembly.
Repair or replace the connector, or repair the damaged harness wire.

STEP 10. Check harness between accelerator pedal position sensor connector terminal and engine-ECU connector terminal APSM.

  • Check output line for open circuit and damage.

Q. Is the check result normal?
Go to Step 4.
Repair or replace the connector, or repair the damaged harness wire.