DTC P1644-00: ECU Malfunction (Starter Circuit) [03/2023 - ]: Procedure

1. Read the DTCs.

   Powertrain > Stop and Start > Trouble Codes 

   Result

   Result	Proceed to
   DTC P1644-00 is output	A
   DTCs P060B-1C, P060B-49 or P060B-71 and P1644-00 are output	B
   DTCs P0615-11 and P1644-00 are output	C

   HINT: 

   If DTCs P060B-1C, P060B-49, P060B-71 or P0615-11 and P1644-00 are output simultaneously, troubleshoot for DTC P060B-1C, P060B-49, P060B-71 or P0615-11 first.

Result: 

B 

GO TO DTC P060B-1C, P060B-49 OR P060B-71. Refer to  DTC P060B-1C: Analog to Digital Converter Circuit Voltage Out of Range; DTC P060B-49: Analog to Digital Converter Internal Electronic Failure; DTC P060B-71: Analog to Digital Converter Actuator Stuck [03/2023 - ]  

Result: 

C 

GO TO DTC P0615-11. Refer to  DTC P0615-11: Starter Relay Circuit Short to Ground [03/2023 - 03/2024]  , or refer to  DTC P0615-11: Starter Relay Circuit Short to Ground [03/2024 - ]  

Result: 

A 

See step  2

1. Disconnect the engine stop and start ECU connector.
2. Remove the ST NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
3. Disconnect the certification ECU (smart key ECU assembly) connector.
4. Disconnect the ECM connector.
5. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A29-21 (STA) - ST NO. 1 relay terminal 2	Always	Below 1 Ω
   A29-21 (STA) - Body ground	Always	10 kΩ or higher
   ST NO. 1 relay terminal 2 - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  3

1. Inspect the ST NO. 1 relay.

   for A25A-FKS: Refer to ON-VEHICLE INSPECTION [11/2021 - ]

   for T24A-FTS: Refer to ON-VEHICLE INSPECTION [11/2021 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE RELAY (ST NO. 1 RELAY) 

Result: 

OK 

See step  4

1. Remove the ST NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   ST NO. 1 relay terminal 1 - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE ENGINE STOP AND START ECU. Refer to  REMOVAL [11/2021 - ] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR