STOP AND START SYSTEM, Diagnostic DTC:P2531

DTC Code DTC Name
P2531 Ignition Switch Run Position Circuit Low

DESCRIPTION

When the engine stop and start ECU receives the OFF signal from the ignition or starter switch assembly*1 or power management control ECU*2 when communication with the ECM is normal, the engine stop and start ECU stores DTC P2531.

  • *1: w/o Entry and Start System

  • *2: w/ Entry and Start System

DTC No.

DTC Detection Condition

Trouble Area

P2531

Both of the following conditions continue for 10 seconds or more (1 trip detection logic):

  • Ignition switch off signal is input.

  • Communication with the ECM is normal.

  • Wire harness or connector

  • EFI MAIN relay

  • Ignition or starter switch assembly (w/o Entry and Start System)

  • Power management control ECU (w/ Entry and Start System)

  • Engine stop and start ECU

CONFIRMATION DRIVING PATTERN

Tip:

DTCs for the stop and start system are not cleared even if the malfunction has been repaired. After repairing the malfunction, be sure to clear the DTCs (Click here).

  1. CONFIRMATION AFTER TROUBLESHOOTING

    Tip:

    • When the cable is disconnected from the negative (-) battery terminal, stop and start control is prohibited for a certain amount of time. After connecting the cable, drive the vehicle until stop and start control is permitted (approximately 15 to 40 minutes).

    • Allow the engine to idle for 3 minutes after the engine warms up and check that the engine speed is within 50 rpm of the target idle speed.

    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON and turn the GTS on.

    3. Clear the DTCs (Click here).

    4. Start the engine and warm it up.

    5. Drive the vehicle at 7 km/h (4.3 mph) or more.

      CAUTION:

      When performing the confirmation driving pattern, obey all speed limits and traffic laws.

    6. Stop the vehicle, move the shift lever to neutral and release the clutch pedal.

    7. Keep the engine stopped by stop and start control for 1 second or more.

    8. Depress the clutch pedal and start the engine.

      Tip:

      If the engine cranks slowly when the engine is restarted, it can be determined that battery voltage is low.

    9. Check that DTCs are not output (Click here).

  2. STOP AND START SYSTEM OPERATION CHECK

    Tip:

    When the cable is disconnected from the negative (-) battery terminal, stop and start control is prohibited for a certain amount of time. After connecting the cable, drive the vehicle until stop and start control is permitted (approximately 15 to 40 minutes).

    1. Start the engine and warm it up.

    2. Turn the air conditioning system off.

    3. Drive the vehicle at 7 km/h (4.3 mph) or more.

      CAUTION:

      When performing the confirmation driving pattern, obey all speed limits and traffic laws.

    4. Stop the vehicle, move the shift lever to neutral and release the clutch pedal.

    5. Allow the engine to stop by stop and start control.

    6. Depress the clutch pedal and start the engine.

WIRING DIAGRAM

A318278E02
A318279E03

CAUTION / NOTICE / HINT

Note:

  • Before replacing the engine stop and start ECU, read the number of starter operations and write it into a new engine stop and start ECU (Click here).

  • After replacing the engine stop and start ECU or air conditioning amplifier assembly, reset and perform learning of the air conditioning information in the engine stop and start ECU (Click here).

  • After replacing the engine stop and start ECU or yaw rate sensor, clear and calibrate the deceleration sensor zero point in the engine stop and start ECU (Click here).

  • Inspect the fuses for circuits related to this system before performing the following procedure.

Tip:

  • DTCs for the stop and start system are not cleared even if the malfunction has been repaired. After repairing the malfunction, be sure to clear the DTCs (Click here).

  • Using the GTS, read the freeze frame data before troubleshooting. System condition information is recorded as freeze frame data the moment a DTC is stored. This information can be useful when troubleshooting (Click here).

PROCEDURE

  1. READ VALUE USING GTS (IG SWITCH)

    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Stop and Start / Data List / IG Switch.

    5. Read the value displayed on the GTS.

      Table 1. Result

      GTS Display

      Result

      Proceed to

      IG Switch

      OFF

      A

      ON

      B

    USE SIMULATION METHOD TO CHECK

    (Click here)

  2. CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - ENGINE ROOM RELAY BLOCK AND JUNCTION BLOCK ASSEMBLY (IG2 RELAY))

    1. Disconnect the ECM connector.

    2. Disconnect the H121 engine stop and start ECU connector.

    3. Disconnect the 1A engine room relay block and junction block assembly connector.

    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      H121-20 (IG2) - 1A-4

      Always

      Below 1 Ω

      H121-20 (IG2) - Body ground

      Always

      10 kΩ or higher

      1A-4 - Body ground

      Always

      10 kΩ or higher

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  3. CHECK HARNESS AND CONNECTOR (BATTERY - IG2 FUSE)

    1. Remove the IG2 fuse from the engine room relay block and junction block assembly.

    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      IG2 fuse terminal 1 - Body ground

      Always

      9.5 to 14 V

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  4. CHECK HARNESS AND CONNECTOR (ENGINE ROOM RELAY BLOCK AND JUNCTION BLOCK ASSEMBLY (IG2 RELAY) - BODY GROUND)

    1. Disconnect the 1A engine room relay block and junction block assembly connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      1A-2 - Body ground

      Always

      Below 1 Ω

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  5. CHECK HARNESS AND CONNECTOR (ENGINE ROOM RELAY BLOCK - IGNITION OR STARTER SWITCH ASSEMBLY OR POWER MANAGEMENT CONTROL ECU)

    1. Disconnect the 1A engine room relay block and junction block assembly connector.

    2. w/o Entry and Start System:

      Disconnect the H6 ignition or starter switch assembly connector.

    3. w/ Entry and Start System:

      Disconnect the H70 power management control ECU connector.

    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      w/o Entry and Start System

      Tester Connection

      Condition

      Specified Condition

      1A-3 - H6-6 (IG2)

      Always

      Below 1 Ω

      1A-3 - Body ground

      Always

      10 kΩ or higher

      H6-6 (IG2) - Body ground

      Always

      10 kΩ or higher

      w/ Entry and Start System

      Tester Connection

      Condition

      Specified Condition

      1A-3 - H70-8 (IG2D)

      Always

      Below 1 Ω

      1A-3 - Body ground

      Always

      10 kΩ or higher

      H70-8 (IG2D) - Body ground

      Always

      10 kΩ or higher

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  6. CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - EFI MAIN RELAY)

    1. Disconnect the A73 engine stop and start ECU connector.

    2. Remove the EFI MAIN relay from the engine room relay block and junction block assembly.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A73-5 (+B) - EFI MAIN relay terminal 3

      Always

      Below 1 Ω

      A73-5 (+B) - Body ground

      Always

      10 kΩ or higher

      EFI MAIN relay terminal 3 - Body ground

      Always

      10 kΩ or higher

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  7. CHECK ECM (IGSW TERMINAL VOLTAGE)

    1. Disconnect the A76 ECM connector.

    2. Turn the ignition switch to ON.

    3. U122211E02

      Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection

      Switch Condition

      Specified Condition

      A76-37 (IGSW) - Body ground

      Ignition switch ON

      9.5 to 14 V
      Table 2. Text in Illustration

      *a

      Front view of wire harness connector

      (to ECM)

    GO TO ECM POWER SOURCE CIRCUIT

    (Click here)

  8. INSPECT RELAY (EFI MAIN RELAY)

    1. Inspect the EFI MAIN relay (Click hereClick here).

    REPLACE RELAY (EFI MAIN RELAY)

  9. CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - ECM)

    1. Remove the EFI MAIN relay from the engine room relay block and junction block assembly.

    2. Disconnect the A76 ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      EFI MAIN relay terminal 2- A76-9 (MREL)

      Always

      Below 1 Ω

      EFI MAIN relay terminal 2- Body ground

      Always

      10 kΩ or higher

      A76-9 (MREL) - Body ground

      Always

      10 kΩ or higher
      Table 3. Result

      Result

      Proceed to

      OK (w/o Entry and Start System)

      A

      OK (w/ Entry and Start System)

      B

      NG

      C

    CHECK POWER MANAGEMENT CONTROL ECU (IG2D TERMINAL VOLTAGE)Click here

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  10. INSPECT IGNITION OR STARTER SWITCH ASSEMBLY

    1. Inspect the ignition or starter switch assembly (Click here).

    REPLACE ENGINE STOP AND START ECU

    (Click here)

    REPLACE IGNITION OR STARTER SWITCH ASSEMBLY

    (Click here)

  11. CHECK POWER MANAGEMENT CONTROL ECU (IG2D TERMINAL VOLTAGE)

    1. Measure the voltage according to the value(s) in the table below.

      U122689E02
      Table 4. Text in Illustration

      *a

      Component without harness connected

      (Power Management Control ECU)

      -

      -

      Standard Voltage

      Tester Connection

      Switch Condition

      Specified Condition

      H70-8 (IG2D) - Body ground

      Ignition switch ACC

      Below 1 V

      H70-8 (IG2D) - Body ground

      Ignition switch ON

      (+B voltage minus 2.0 V) or higher
      Table 5. Result

      Result

      Proceed to

      OK

      A

      NG (for LHD)

      B

      NG (for RHD)

      C

    REPLACE ENGINE STOP AND START ECU

    (Click here)

    REPLACE POWER MANAGEMENT CONTROL ECU

    (Click here)

    REPLACE POWER MANAGEMENT CONTROL ECU

    (Click here)