DTC P1B4B-73: Hybrid/EV Battery Heater Relay Actuator Stuck Closed [03/2023 - ]: Procedure

Pre-procedure1

1. Turn the ignition switch off and turn on the high beam headlights for 30 seconds. This will remove the surface charge from the auxiliary battery.

   Procedure1

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   Positive (+) auxiliary battery terminal - Negative (-) auxiliary battery terminal	20°C (68°F), Ignition switch off	11.0 V or higher

   Result

   Proceed to
   OK
   NG

   Post-procedure1

3. None

Result: 

NG 

See step  11

Result: 

OK 

See step  2

Pre-procedure1

1. None

   Procedure1

2. Check for DTCs.

   Powertrain > HV Battery > Trouble Codes 

   Powertrain > Hybrid Control > Trouble Codes 

   Result

   Result	Proceed to
   "P1B4B-73" only is output, or DTCs except the ones in the table below are also output.	A
   DTCs of hybrid battery system in the table below are output.	B
   DTCs of hybrid control system in the table below are output.	C

   System	Relevant DTC
   Hybrid battery system	P060A-47	Hybrid/EV Battery Energy Control Module Monitoring Processor Watchdog / Safety MCU Failure
   	P060B-49	Hybrid/EV Battery Energy Control Module A/D Processing Internal Electronic Failure
   	P0606-87	Hybrid/EV Battery Energy Control Module Processor to Monitoring Processor Missing Message
   Hybrid control system	P0A1F-94	Hybrid/EV Battery Energy Control Module Unexpected Operation

   Post-procedure1

3. Turn the ignition switch off.

Result: 

B 

GO TO DTC CHART (HYBRID BATTERY SYSTEM). Refer To  DIAGNOSTIC TROUBLE CODE CHART [03/2023 - ] 

Result: 

C 

GO TO DTC CHART (HYBRID CONTROL SYSTEM) 

Refer to DIAGNOSTIC TROUBLE CODE CHART [03/2023 - 01/2025] , or refer to DIAGNOSTIC TROUBLE CODE CHART [01/2025 - ]

Result: 

A 

See step  3

Refer to PROCEDURE - Step 2

Result

Result: 

NG 

CONNECT SECURELY 

Result: 

OK 

See step  4

Refer to PROCEDURE - Step 3

Result

Result: 

NG 

CONNECT SECURELY 

Result: 

OK 

See step  5

Pre-procedure1

1. Check that the service plug grip is not installed.
   NOTE:

   After removing the service plug grip, do not turn the ignition switch to ON (READY), unless instructed by the repair information because this may cause a malfunction.

2. Connect the SST.

   HINT: 

   Refer to Instructions for Connecting SST [03/2023 - ] 

3. Connect the cable to the negative (-) auxiliary battery terminal.
4. Turn the ignition switch to ON.

   Procedure1

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   x14-11 (BHR) - Body ground	Ignition switch ON	Below 1 V

   NOTE:

   • Turning the ignition switch to ON with the service plug grip removed causes other DTCs to be stored. Clear the DTCs after performing this inspection.
   • If the ignition switch is turned to ON with the connectors disconnected, other DTCs will be stored. Be sure to clear the DTCs after the inspection.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Component with harness connected (to No. 1 Traction Battery Heater Relay)

   Result

   Proceed to
   OK
   NG

   Post-procedure1

6. Turn the ignition switch off.
7. Disconnect the cable from the negative (-) auxiliary battery terminal.
8. Disconnect the SST.

Result: 

NG 

See step  10

Result: 

OK 

See step  6

Refer to PROCEDURE - Step 3

Result

Result: 

NG 

See step  9

Result: 

OK 

See step  7

Refer to PROCEDURE - Step 4

Result

Result: 

OK 

REPLACE NO. 1 TRACTION BATTERY HEATER RELAY 

Refer to REMOVAL [03/2023 - ]

Result: 

NG 

See step  8

Refer to PROCEDURE - Step 5

Result

Result: 

OK 

REPLACE NO. 1 TRACTION BATTERY HEATER 

Refer to REMOVAL [03/2023 - ]

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Refer to PROCEDURE - Step 6

Result

Result: 

OK 

REPLACE NO. 1 TRACTION BATTERY HEATER 

Refer to REMOVAL [03/2023 - ]

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Pre-procedure1

1. Check that the service plug grip is not installed.
   NOTE:

   After removing the service plug grip, do not turn the ignition switch to ON (READY), unless instructed by the repair information because this may cause a malfunction.

2. Connect the SST.

   HINT: 

   Refer to Instructions for Connecting SST [03/2023 - ] 

3. Disconnect the No. 1 traction battery heater relay connector.
   NOTE:

   Before disconnecting the connector, check that it is not loose or disconnected.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

4. Disconnect the battery ECU assembly connector.
   NOTE:

   Before disconnecting the connector, check that it is not loose or disconnected.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

5. Connect the cable to the negative (-) auxiliary battery terminal.
6. Turn the ignition switch to ON.

   Procedure1

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   X14-11 (BHR) or x4-12 (BHRB) - Body ground	Ignition switch ON	Below 1 V

   NOTE:

   • Turning the ignition switch to ON with the service plug grip removed causes other DTCs to be stored. Clear the DTCs after performing this inspection.
   • If the ignition switch is turned to ON with the connectors disconnected, other DTCs will be stored. Be sure to clear the DTCs after the inspection.

   Result

   Proceed to
   OK
   NG

   Post-procedure1

8. Turn the ignition switch off.
9. Disconnect the cable from the negative (-) auxiliary battery terminal.
10. Reconnect the battery ECU assembly connector.
11. Reconnect the No. 1 traction battery heater relay connector.
12. Disconnect the SST.

Result: 

OK 

REPLACE BATTERY ECU ASSEMBLY 

Refer to REMOVAL [03/2023 - ]

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

1. Charge or replace the auxiliary battery.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  2