DTC    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):
  1. Malfunction in the engine stop and start ECU internal drive circuit for the starter.
  1. Harness or connector
  2. ST relay
  3. Engine stop and start ECU

HINT:
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).


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

HINT:
  1. If the ECM learned values have been cleared by disconnecting the battery or for another reason, Stop and Start system control will be prohibited until ECM learning completes.
  2. 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 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 and stop the vehicle to allow the engine to stop due to Stop and Start system control.

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

  6. Check that no DTCs are output (Click here).


Check if the Stop and Start system operates normally.

HINT:
If the battery terminal has been disconnected, the ECO OFF indicator will be illuminated. In this case, drive the vehicle for 15 to 40 minutes to turn off the indicator.

  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.


WIRING DIAGRAM


A217700E01


A217701E01


INSPECTION PROCEDURE

NOTICE:
  1. If the engine stop and start ECU is being replaced, register the previously recorded number of starter operations into the new engine stop and start ECU (Click here).
  2. 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).
  3. Inspect the fuses for circuits related to this system before performing the following inspection procedure.

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

  1. Disconnect engine stop and start ECU connector.

  1. Remove the ST relay from the No. 1 engine room relay block.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    D79-1 (STA) - ST relay terminal 2
    		Always
    		Below 1 Ω
    D79-1 (STA) - Body ground
    		Always
    		10 kΩ or higher
    ST relay terminal 2- Body ground
    		Always
    		10 kΩ or higher

  1. Reconnect the engine stop and start ECU connector.

  1. Reinstall the ST relay.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


2.CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - CLUTCH START SWITCH)

  1. Disconnect engine stop and start ECU connector.

  1. Disconnect the clutch start switch (lower) connector.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    D79-1 (STA) - A29-1
    		Always
    		Below 1 Ω
    D79-1 (STA) - Body ground
    		Always
    		10 kΩ or higher
    A29-1 - Body ground
    		Always
    		10 kΩ or higher

  1. Reconnect the engine stop and start ECU connector and clutch start switch 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 No. 1 engine room relay block.

  1. 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

  1. Reinstall the ST relay.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


4.INSPECT ST RELAY

  1. Remove the ST relay from the No. 1 engine room relay block.



    B016200E52

  1. 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

    Text in Illustration 
    *1
    		ST Relay:



NG
REPLACE ST RELAY
OK

REPLACE ENGINE STOP AND START ECU (Click here)