DTC P323A-19: Backup Boost Converter "A" Circuit Current Above Threshold [11/2021 - 03/2023]: Procedure
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2025 Lexus NX 350, 2025 Lexus NX 250, 2024 Lexus NX 350, 2024 Lexus NX 250, and 2023 Lexus NX 350. However, it is still accessible from the selected car via links, so may be relevant.
- CHECK DTC OUTPUT (ENGINE CONTROL SYSTEM)
- Read the DTCs
Powertrain > Engine > Trouble Codes
Result
Result Proceed to DTC P323A-19 is output A DTC P2796-12, P2796-14 or P2796-97 and P323A-19 is output B HINT:
If any DTCs other than P2796-12, P2796-14 or P2796-97 are output, troubleshoot those DTCs first.
Result:
B
GO TO DIAGNOSTIC TROUBLE CODE CHART. Refer to DIAGNOSTIC TROUBLE CODE CHART [11/2021 - 03/2023]
Result:
A
See step 2
- Read the DTCs
- CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - BBC NO. 1, BBC NO. 2 FUSES)
- Disconnect the engine stop and start ECU connector.
- Remove the BBC NO. 1 and BBC NO. 2 fuses from the No. 1 engine room relay block and No. 1 junction block assembly.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition A28-1 (BIN2) - BBC NO. 2 fuse terminal 2 Always Below 1 Ω A28-3 (BIN1) - BBC NO. 1 fuse terminal 2 Always Below 1 Ω A28-1 (BIN2) - Body ground Always 10 kΩ or higher BBC NO. 2 fuse terminal 2 - Body ground Always 10 kΩ or higher A28-3 (BIN1) - Body ground Always 10 kΩ or higher BBC NO. 1 fuse 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
- CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - EACH ECU OR SENSOR)
- Disconnect the engine stop and start ECU connector.
- Disconnect the meter mirror sub-assembly connector.
- Disconnect the clearance warning ECU assembly connector.
- Disconnect the room light control relay connector.
- Disconnect the DOME CUT NO. 2 relay connector.
- Disconnect the tire pressure warning ECU and receiver connector.
- Disconnect the inner rear view mirror assembly LH connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition D40-3 (IG41) - D8-10 (IG) Always Below 1 Ω D40-3 (IG41) - G114-1 (IG) Always Below 1 Ω D40-3 (IG41) - G90-1 (IG) Always Below 1 Ω D40-2 (B41) - D80-1 (+B) Always Below 1 Ω D40-2 (B41) - 5 (DOME CUT NO. 2 relay) Always Below 1 Ω D40-11 (B43) - G90-7 (+B) Always Below 1 Ω D40-11 (B43) - M4-6 (+B) Always Below 1 Ω D40-3 (IG41) - Body ground Always 10 kΩ or higher D40-2 (B41) - Body ground Always 10 kΩ or higher D40-11 (B43) - Body ground Always 10 kΩ or higher Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
Result:
OK
See step 4
- CHECK ENGINE STOP AND START ECU
- Disconnect the engine stop and start ECU connectors.
*a Component without harness connected
(Engine Stop and Start ECU)- - - Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition D40-3 (IG41) - A29-6 (DGND) Always 10 kΩ or higher D40-2 (B41) - A29-6 (DGND) Always 10 kΩ or higher D40-11 (B43) - A29-6 (DGND) Always 10 kΩ or higher Result
Proceed to OK NG
Result:
NG
REPLACE ENGINE STOP AND START ECU. Refer to REMOVAL [11/2021 - ]
Result:
OK
See step 5
- Disconnect the engine stop and start ECU connectors.
- CHECK VEHICLE CONDITION (B41, B43 AND IG41 CIRCUIT)
- Check that additional devices installed to the vehicle (aftermarket audio system, etc.) are not connected to the B41, B43 or IG41 terminal circuit of the engine stop and start ECU.
Result
Result Proceed to Load from an additional device installed to the vehicle (aftermarket audio system, etc.) is not applied. A Load from an additional device installed to the vehicle (aftermarket audio system, etc.) is applied. B
Result:
A
TROUBLESHOOT ECUS CONNECTED TO TERMINALS B41, B43 AND IG41
Result:
B
END (REMOVE ADDITIONAL DEVICE)
- Check that additional devices installed to the vehicle (aftermarket audio system, etc.) are not connected to the B41, B43 or IG41 terminal circuit of the engine stop and start ECU.