Code No. P0502: Vehicle Speed Sensor Low Input










OPERATION



  • Power is supplied to the vehicle speed sensor (terminal No. 1) from the ignition switch (terminal No. 2) and is earthed to the vehicle body from the vehicle speed sensor (terminal No. 2).
  • A power voltage of 5 V is applied to the vehicle speed sensor (terminal No. 3) from the engine-ECU (terminal No. 141).

FUNCTION



  • The vehicle speed sensor converts the vehicle speed to the voltage, and then input it into the engine-ECU

TROUBLE JUDGMENT


Check Conditions
  • Engine is running
  • Engine coolant temperature is 80°C or higher
  • The last fuel injection rate exceeds the specified value.
  • Engine speed is 2,900 r/min or more.
Judgment Criterion
  • Vehicle speed is 5 km/h or lower for 2 seconds.

PROBABLE CAUSES



  • Failed vehicle speed sensor
  • Open/short circuit or harness damage in vehicle speed 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 4: Vehicle speed sensor

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-16 vehicle speed sensor connector

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

STEP 3. Perform voltage measurement at C-16 vehicle speed sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 3 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: D-215 engine-ECU connector

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

STEP 5. Check harness between C-16 (terminal No. 3) vehicle speed sensor connector and B-08 (terminal No. 141) engine-ECU connector.
note Before checking harness, check intermediate connectors D-228, D-37, D-230, and repair if necessary.

  • Check output 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 4: Vehicle speed sensor

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 closed type DPF carries out the forcible DPF regeneration. (Refer to GROUP 17 - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).

STEP 7. Perform voltage measurement at C-16 vehicle speed sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 1 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 9 .
Go to Step 8 .

STEP 8. Connector check: D-309 ignition switch connector

Q. Is the check result normal?

    Check intermediate connectors D-228, D-405, D-403, and repair if necessary. If intermediate connectors are normal, check and repair harness between C-16 (terminal No. 1) vehicle speed sensor connector and D-309 (terminal No. 2) ignition switch connector.

    • Check power supply line for open/short circuit.
Repair or replace the connector.

STEP 9. Perform resistance measurement at C-16 vehicle speed 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 .

    Check and repair harness between C-16 (terminal No. 2) vehicle speed sensor connector and body earth.

    • Check earthing line for open circuit and damage.

STEP 10. Connector check: D-309 ignition switch connector

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

STEP 11. Check harness between C-16 (terminal No. 1) vehicle speed sensor connector and D-309 (terminal No. 2) ignition switch connector.
note Before checking harness, check intermediate connectors D-228, D-405, D-403, and repair if necessary.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 12 .
Repair the damaged harness wire.

STEP 12. Check harness between C-16 (terminal No. 3) vehicle speed sensor connector and B-08 (terminal No. 141) engine-ECU connector.
note Before checking harness, check intermediate connectors D-228, D-37, D-230, and repair if necessary.

  • Check output line for damage.

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