STOP AND START SYSTEM, Diagnostic DTC:P1644

DTC Code DTC Name
P1644 ECU Internal Error

DESCRIPTION

If any malfunction is detected in the engine stop and start ECU internal drive circuit for the starter, this DTC will be stored.

This DTC may also be stored due to an open or short in an external wire harness.

DTC No. DTC Detection Condition Trouble Area
P1644

The following condition continues for 0.2 seconds or more (1 trip detection logic):


  • Malfunction in the engine stop and start ECU internal drive circuit for the starter.

  • Harness or connector

  • ST relay

  • Engine stop and start ECU

  1. After troubleshooting, perform the following steps to recheck for DTCs and check if the Stop and Start system operates normally.

    Tech Tips


    • If the battery terminal has been disconnected, the stop and start will be prohibited. In this case, drive the vehicle for 15 to 40 minutes to permit the stop and start operation.

    • 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. for Manual Transaxle


      1. Connect the intelligent tester to the DLC3.

      2. Clear the DTCs Click here.

      3. Start the engine and warm it up.

      4. Drive the vehicle at 20 km/h (12.4 mph) or more.

      5. Stop the vehicle, allow the engine to stop due to Stop and Start system control and wait for 3 seconds or more.

      6. Depress the clutch pedal to allow the engine to restart.

        Tech Tips

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

      7. Check that no DTCs are output Click here.

    2. for CVT


      1. Connect the intelligent tester to the DLC3.

      2. Clear the DTCs Click here.

      3. Start the engine and warm it up.

      4. Drive the vehicle at 20 km/h (12.4 mph) or more.

      5. Stop the vehicle, allow the engine to stop due to Stop and Start system control and wait for 3 seconds or more.

      6. Release the brake pedal to allow the engine to restart. (with the shift lever in D)

        Tech Tips

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

      7. Check that no DTCs are output Click here.

  2. Check if the Stop and Start system operates normally.

    Tech Tips

    If the battery terminal has been disconnected, the stop and start will be prohibited. In this case, drive the vehicle for 15 to 40 minutes to permit the stop and start operation.


    1. for Manual Transaxle


      1. Warm up the engine.

      2. Turn the air conditioning system off.

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

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

      5. Check that the engine stops.

      6. Depress the clutch pedal and check that the engine restarts.

    2. for CVT


      1. Warm up the engine.

      2. Turn the air conditioning system off.

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

      4. Stop the vehicle with the shift lever in D and depressed the brake pedal.

      5. Check that the engine stops.

      6. Release the brake pedal and check that the engine restarts.

WIRING DIAGRAM

Refer to P1545 Click here.

CAUTION / NOTICE / HINT

Note


  • If the engine stop and start ECU is being replaced, download the number of starter operations to the tester from the old ECU before removing it, and then upload the number of starter operations from the tester to the new engine stop and start ECU after installing the ECU Click here.

  • After the engine stop and start ECU is replaced or after an air conditioner kit is installed, clear the A/C information stored in the engine stop and start ECU Click here.

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

  • After the engine stop and start ECU or airbag sensor assembly (yaw rate sensor) is replaced, initialize and calibrate 0 point of deceleration sensor Click here.

Tech Tips

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.

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - ENGINE ROOM RELAY BLOCK)


    1. Disconnect the A53 engine stop and start ECU connector.

    2. Remove the ST relay from the engine room main relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A53-4 (STA) - ST relay terminal 2 Always Below 1 Ω
      A53-4 (STA) - Body ground Always 10 kΩ or higher
      ST relay terminal 2- Body ground Always 10 kΩ or higher

      Reinstall the ST relay to the engine room main relay block.

      Result
      Result Proceed to
      OK (for Manual Transaxle) A
      OK (for CVT)) B
      NG C

    B

    CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - PARK/NEUTRAL POSITION SWITCH ASSEMBLY) Click here

    C

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    A

  2. CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - NO. 2 CLUTCH START SWITCH ASSEMBLY)


    1. Disconnect the A39 No. 2 clutch start switch assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A53-4 (STA) - A39-1 Always Below 1 Ω
      A53-4 (STA) - Body ground Always 10 kΩ or higher
      A39-1 - Body ground Always 10 kΩ or higher

    3. Reconnect A53 engine stop and start ECU connector.

    4. Reconnect the A39 No. 2 clutch start switch assembly connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK HARNESS AND CONNECTOR (ST RELAY - BODY GROUND)


    1. Remove the ST relay from the engine room main relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      ST relay terminal 1 - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. INSPECT ST RELAY


    1. A01VL26E01

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      3 - 5 Battery voltage not applied 10 kΩ or higher
      Battery voltage applied to terminals 1 and 2 Below 1 Ω

    2. Reinstall the ST relay to the engine room relay block.


    OK

    REPLACE ENGINE STOP AND START ECU Click here

    NG

    REPLACE ST RELAY

  5. CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - PARK/NEUTRAL POSITION SWITCH ASSEMBLY)


    1. Disconnect A53 engine stop and start ECU connector.

    2. Disconnect the B69 park/neutral position switch assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A53-4 (STA) - B69-9 (L) Always Below 1 Ω
      A53-4 (STA) - Body ground Always 10 kΩ or higher
      B69-9 (L) - Body ground Always 10 kΩ or higher

    4. Reconnect A53 engine stop and start ECU connector.

    5. Reconnect the B69 park/neutral position switch assembly connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  6. CHECK HARNESS AND CONNECTOR (ST RELAY - BODY GROUND)


    1. Remove the ST relay from the engine room main relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      ST relay terminal 1 - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  7. INSPECT ST RELAY


    1. A01VL26E01

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      3 - 5 Battery voltage not applied 10 kΩ or higher
      Battery voltage applied to terminals 1 and 2 Below 1 Ω

    2. Reinstall the ST relay to the engine room main relay block.


    OK

    REPLACE ENGINE STOP AND START ECU Click here

    NG

    REPLACE ST RELAY