Power Source/wiring: Overview Lexus LS IV

SYSTEM DESCRIPTION

1. DESCRIPTION The electric power control system is provided to supply power constantly to the vehicle equipped with many electronic systems. The electric power control ECU always monitors the battery condition. In accordance with the battery condition, the electric power control ECU implements various control measures on systems that operate while the vehicle is parked or systems that require a large amount of power in a short period of time.
2. RECHARGE CONTROL While the engine is running, the electric power control ECU monitors the battery recharging state. The ECU then adjusts the generated voltage so that the actual current value is close to the target current value. The ECU sends recharging control signals to the ECM via CAN communication.
3. LOAD CONTROL While the engine is running, the electric power control ECU temporarily limits the power consumption of large systems to optimize the battery recharging state. The ECU sends load control signals to load control related systems via CAN communication.
4. POWER SAVE CONTROL WHILE PARKED Depending on the amount of time the vehicle is parked, the electric power control ECU cuts power to systems that it determines to be unnecessary. The electric power control ECU uses the power cut relay to control power supplied to power cut linked parts.
5. MESSAGE OF CHARGING SYSTEM Details DETAILS CHART Condition that leads to display Timing Display details Master caution operation Buzzer operation Generator malfunction When malfunction is detected Check Generator Have your vehicle checked by a dealer - Sound Load control operation When load control is performed Electrical equipment operation is limited - - Battery voltage drop When parked, electrical equipment usage leads to battery voltage drop Low Battery Start the engine Illuminate - Battery voltage detection malfunction When malfunction in battery voltage detection is detected Check Power Control System Have your vehicle checked by a dealer

OPERATION CHECK

1. CHECK LOAD CONTROL HISTORY Using the Techstream, read the Data List. Electric Power Control ELECTRIC POWER CONTROL REFERENCE CHART Item Measurement Item/Display (Range) Normal Condition Diagnostic Note Ctrl Load Lv1 History Load control level 1 history count/ 0 to 255 History count until now - Ctrl Load Lv3 History Load control level 3 history count/ 0 to 255 History count until now - OK: No load control history (each system may have malfunction) NG: There is load control history (check charging system (see «ON-VEHICLE INSPECTION» ))

DESCRIPTION

The electric power control ECU monitors the IG (IG2) voltage. When there is no voltage input to IG (IG2), this DTC is output.

DTC DETECTION CONDITION CHART

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1. CHECK PASSENGER SIDE JUNCTION BLOCK (IG INPUT VOLTAGE) Disconnect the PK junction block connector. Measure the voltage according to the value (s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Switch Condition Specified Condition PK-1 (IG) - Body ground Engine switch on (IG) 11 to 14 V NG: Go to step 3 OK: Go to next step
2. INSPECT FUSE (P IG2) Remove the P IG2 fuse from the passenger side junction block. Measure the resistance of the fuse. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition P IG2 fuse Always Below 1 ohms NG: REPLACE FUSE OK: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU)
3. CHECK HARNESS AND CONNECTOR (PASSENGER SIDE J/B - ENGINE ROOM NO. 2 J/B) Disconnect the PK and 2C junction block connectors. Measure the resistance according to the value (s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition PK-1 (IG) - 2C-30 Always Below 1 ohms PK-1 (IG) or 2C-30 - Body ground Always 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
4. CHECK HARNESS AND CONNECTOR (ENGINE ROOM NO. 2 JUNCTION BLOCK BATTERY) Disconnect the 2E junction block connector. Measure the voltage according to the value (s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Condition Specified Condition 2E-1 - Body ground Always 11 to 14 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
5. INSPECT FUSE (P-J/B) Remove the P-J/B fuse from the engine room No. 2 junction block. Measure the resistance of the fuse. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition P-J/B fuse Always Below 1 ohms NG: REPLACE FUSE OK: Go to next step
6. CHECK FOR DTC (B2273) Check for DTC B2273 (see «DTC CHECK/CLEAR» ). OK: DTC B2273 is not output. NG: GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Starting) (See «DIAGNOSTIC TROUBLE CODE CHART» ) OK: REPLACE ENGINE ROOM NO. 2 JUNCTION BLOCK

The battery current sensor converts current to voltage, and outputs the value to the electric power control ECU. The electric power control ECU detects the battery condition, and performs load control and generator control.

DTC DETECTION CONDITION CHART

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1. READ VALUE USING TECHSTREAM (BATTERY CURRENT) Put the vehicle in a no load test condition. Then set the headlights to high beam, set the heater blower switch to Hi, and run the engine at 2000 rpm. Using an electrical tester and probes, measure the current. Using the Techstream, read the Data List. Electric Power Control ELECTRIC POWER CONTROL REFERENCE CHART Item Measurement Item/Display (Range) Normal Condition Diagnostic Note Electrical Charge Current Current battery current value display/ Min.:-300, Max.: 100 [A] Amperage value is displayed - OK: Values of electrical tester and the Techstream are almost the same. NG: Go to step 4 OK: Go to next step
2. INSPECT BATTERY CURRENT SENSOR ASSEMBLY (TEMPERATURE SENSOR VOLTAGE) Disconnect the A49 sensor connector. Measure the resistance according to the value (s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition A49-1 (THB) - A49-4 (E2) 20 to 30°C (68 to 86°F) 1.5 to 2.1 kohms (0 to 70°C (32 to 158°F)) (0.3 to 6.0 kohms) NOTE: The temperature shown in the inspection condition is for the area surrounding the sensor, not the sensor itself. NG: REPLACE BATTERY CURRENT SENSOR ASSEMBLY (See «REMOVAL» ) OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (ELECTRIC POWER CONTROL ECU - BATTERY CURRENT SENSOR) Disconnect the A69 ECU connector. Disconnect the A49 sensor connector. Measure the resistance according to the value (s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition A69-20 (THB) - A49-1 (THB) Always Below 1 ohms A69-20 (THB) or A49-1 (THB) - Body ground Always 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU)
4. CHECK BATTERY CURRENT SENSOR ASSEMBLY (VC5 VOLTAGE) Disconnect the A49 sensor connector. Measure the voltage according to the value (s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Switch Condition Specified Condition A49-2 (VC5) - A49-4 (E2) Engine switch on (IG) 4.5 to 5.5 V OK: Go to step 6 NG: Go to next step
5. CHECK HARNESS AND CONNECTOR (ELECTRIC POWER CONTROL ECU - BATTERY CURRENT SENSOR) Disconnect the A69 ECU connector. Disconnect the A49 sensor connector. Measure the resistance according to the value (s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition A69-6 (VC) - A49-2 (VC5) Always Below 1 ohms A69-10 (E2) - A49-4 (E2) Always Below 1 ohms A69-6 (VC) or A49-2 (VC5) - Body ground Always 10 kohms or higher A69-10 (E2) or A49-4 (E2) - Body ground Always 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU)
6. CHECK HARNESS AND CONNECTOR (ELECTRIC POWER CONTROL ECU - BATTERY CURRENT SENSOR) Disconnect the A69 ECU connector. Disconnect the A49 sensor connector. Measure the resistance according to the value (s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition A69-9 (IB) - A49-3 (IB) Always Below 1 ohms A69-9 (IB) or A49-3 (IB) - Body ground Always 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
7. CHECK BATTERY CURRENT SENSOR ASSEMBLY (OPERATION) Temporarily replace the battery current sensor with a new or normally functioning one (see «REMOVAL» ). Delete the DTC (see «DTC CHECK/CLEAR» ). Check for DTC again (see «DTC CHECK/CLEAR» ). OK: No DTC is output. NG: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU) OK: END (BATTERY CURRENT SENSOR IS DEFECTIVE)

The battery temperature sensor inside the current sensor detects changes in temperature as resistance values. In other words, when the temperature increases, the voltage decreases.

DTC DETECTION CONDITION CHART

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1. INSPECT BATTERY CURRENT SENSOR ASSEMBLY Disconnect the A49 sensor connector. Measure the resistance according to the value (s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition A49-1 (THB) - A49-4 (E2) 20 to 30°C (68 to 86°F) 1.5 to 2.1 kohms (0 to 70°C (32 to 158°F)) (0.3 to 6.0 kohms) NOTE: The temperature shown in the inspection condition is for the area surrounding the sensor, not the sensor itself. NG: REPLACE BATTERY CURRENT SENSOR ASSEMBLY (See «REMOVAL» ) OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (ELECTRIC POWER CONTROL ECU - BATTERY CURRENT SENSOR) Disconnect the A69 ECU connector. Disconnect the A49 sensor connector. Measure the resistance according to the value (s) in the table below. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition A69-20 (THB) - A49-1 (THB) Always Below 1 ohms A69-20 (THB) or A49-1 (THB) - Body ground Always 10 kohms or higher NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU)

The electric power control ECU inputs the battery voltage. The electric power control ECU receives several signals and detects the battery condition, and performs load control and generator control.

DTC DETECTION CONDITION CHART

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1. READ VALUE USING TECHSTREAM (BATTERY VOLTAGE) Using the Techstream, read the Data List. Electric Power Control ELECTRIC POWER CONTROL REFERENCE CHART Item Measurement Item/Display (Range) Normal Condition Diagnostic Note Battery Voltage Current battery voltage value display/ Min.: 0, Max.: 16.67 [V] Battery voltage is displayed - OK: 11 to 14 V NG: Go to step 2 OK: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU)
2. INSPECT FUSE (VSSR) Remove the VSSR fuse from the engine room No. 1 relay block. Measure the resistance of the fuse. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition VSSR fuse Always Below 1 ohms NG: REPLACE FUSE OK: Go to next step
3. CHECK ELECTRIC POWER CONTROL ECU (VB+ INPUT VOLTAGE) Disconnect the A69 ECU connector. Measure the voltage according to the value (s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Condition Specified Condition A69-18 (VB+) - A69-8 (VB-) Always 11 to 14 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU)

The electric power control ECU inputs the STSW signal, and detects when the engine is started.

DTC DETECTION CONDITION CHART

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1. CHECK ELECTRIC POWER CONTROL ECU (STSW SIGNAL) Disconnect the A69 ECU connector. Measure the voltage according to the value (s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Switch Condition Specified Condition A69-12 (STSW) - Body ground Engine switch on (IG) --> cranking Below 1 V --> 8 to 14 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR (PASSENGER SIDE JUNCTION BLOCK - MAIN BODY ECU) OK: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU)

The electric power control ECU receives the ECM's generator control signal, compares the value with the battery current and battery voltage signals, and detects generator generation malfunctions.

DTC DETECTION CONDITION CHART

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The electric power control ECU receives the ECM's generator control signal, compares the value with the battery current and battery voltage signals, and detects generator charging line malfunctions.

DTC DETECTION CONDITION CHART

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1. CHECK GENERATOR ASSEMBLY (TERMINAL B) Check the generator's tightening torque value. Standard torque STANDARD TORQUE REFERENCE CHART Generator Standard torque Terminal 1 (B) 12 N*m (122 kgf*cm, 8.82 ft.*lbf) NG: TIGHTEN GENERATOR ASSEMBLY (TERMINAL B) OK: Go to next step
2. CHECK GENERATOR ASSEMBLY (IG INPUT VOLTAGE) Disconnect the E24 generator connector. Measure the resistance according to the value (s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Switch Condition Specified Condition E24-2 (IG) - Body ground Engine switch on (IG) 11 to 14 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU)

The power cut relay is built into the power electric control ECU. When the vehicle is parked for an extended period of time, the power electric control ECU turns the power cut relay OFF, which cuts power to the power cut linked parts.

DTC DETECTION CONDITION CHART

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1. INSPECT FUSE (P-D/C CUT) Remove the P-D/C CUT fuse from the passenger side junction block. Measure the resistance of the fuse. Standard resistance STANDARD RESISTANCE REFERENCE CHART Tester Connection Condition Specified Condition P-D/C CUT fuse Always Below 1 ohms NG: REPLACE FUSE OK: Go to next step
2. CHECK PASSENGER SIDE JUNCTION BLOCK (BCUT INPUT VOLTAGE) Disconnect the PM junction block connector. Measure the voltage according to the value (s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Condition Specified Condition PM-1 (BCUT) - Body ground Always 11 to 14 V NG: REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
3. CHECK PASSENGER SIDE JUNCTION BLOCK (CUTD OUTPUT VOLTAGE) Measure the voltage according to the value (s) in the table below. Standard voltage STANDARD VOLTAGE REFERENCE CHART Tester Connection Switch Condition Specified Condition PA-57 or PA-35 (CUTD) - Body ground Engine switch on (IG) 11 to 14 V NG: REPLACE PASSENGER SIDE JUNCTION BLOCK OK: Go to next step
4. CHECK FOR DTC Delete the DTC (see «DTC CHECK/CLEAR» ). Check for the DTC again (see «DTC CHECK/CLEAR» ). OK: DTC is not output. NG: REPLACE PASSENGER SIDE JUNCTION BLOCK (ELECTRIC POWER CONTROL ECU) OK: END

The electric power control ECU receives engine related signals from the ECM via CAN communication.

DTC DETECTION CONDITION CHART

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The electric power control ECU receives vehicle speed signals from the skid control ECU via CAN communication.

DTC DETECTION CONDITION CHART

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These DTCs are output when the CAN communication system is judged to be malfunctioning.

DTC DETECTION CONDITION CHART

See also:
• CAN COMMUNICATION SYSTEM
• HOW TO PROCEED WITH TROUBLESHOOTING
• REMOVAL