Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Brake Switch "B" Circuit Short to Battery (P070312)

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual / Drivetrain / U881e (automatic Transmission / Transaxle) / Automatic Transaxle System / Brake Switch "B" Circuit Short to Battery (P070312)

DESCRIPTION

The purpose of the stop light switch signal circuit is to prevent the engine from stalling when the brakes are suddenly applied while driving in the lock-up condition.

When the brake pedal is depressed, the stop light switch assembly sends a signal to the ECM. The ECM then cancels the operation of the lock-up clutch while braking is in progress.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

Note

P070312

Brake Switch "B" Circuit Short to Battery

1. Diagnosis Condition 2. Malfunction Status 3. Malfunction Time 4. Other

  • The engine switch is on (IG) and battery voltage is 8 V or more.
  • The stop light switch remains on.
  • The vehicle is driven in a GO (30 km/h (19 mph) or more) and STOP (less than 3 km/h (2 mph)) pattern 5 times
  • 2-trip detection logic
  • Stop light switch assembly
  • Short in stop light switch signal circuit
  • ECM

Comes on

DTC stored

SAE Code:

P0724

MONITOR DESCRIPTION

This DTC indicates that the stop light switch is remaining on. When the stop light switch remains on during GO and STOP driving, the ECM interprets this as a malfunction of the stop light switch assembly, illuminates the MIL and stores this DTC. The vehicle must GO (30 km/h (19 mph) or more) and STOP (less than 3 km/h (2 mph)) 5 times for 2 consecutive driving cycles in order for this DTC to be stored.

MONITOR STRATEGY

Related DTCs

P0724: Stop light switch/Verify switch input

Required sensors/Components

Stop light switch

Frequency of operation

Continuous

Duration

GO and STOP 5 times

MIL operation

2 driving cycles

Sequence of operation

None

TYPICAL ENABLING CONDITIONS

The stop light switch remains on during GO and STOP driving 5 times.

GO and STOP are defined as follows:

The monitor will run whenever the following DTCs are not present

None

GO (Vehicle speed is 30 km/h (18.65 mph) or more)

Once

STOP (Vehicle speed is less than 3 km/h (1.86 mph))

Once

Battery voltage

8 V or more

Engine switch

On (IG)

Starter

OFF

TYPICAL MALFUNCTION THRESHOLDS

Stop light switch

ON

CONFIRMATION DRIVING PATTERN

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT:

  • After repairs have been completed, clear the DTCs and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
  • When clearing the permanent DTCs, refer to the Clear Permanent DTC procedure.

    Click here

  1. Connect the Techstream to the DLC3.
  2. Turn the engine switch on (IG) and turn the Techstream on.
  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
  4. Turn the engine switch off and wait for 2 minutes or more.
  5. Turn the engine switch on (IG) and turn the Techstream on.
  6. Start the engine.
  7. Repeat the following procedure 5 times [*1]:
    • Accelerate the vehicle to 30 km/h (19 mph) or more, depress the brake pedal and decelerate the vehicle to 3 km/h (2 mph) or less.

      HINT:

      [*1] : Normal judgment procedure.

      The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.

  8. Stop the vehicle.
  9. Enter the following menus: Powertrain / Transmission / Utility / All Readiness.
  10. Input the DTC: P070312.
  11. Check the DTC judgment result.

    Techstream Display

    Description

    NORMAL
    • DTC judgment completed
    • System normal

    ABNORMAL
    • DTC judgment completed
    • System abnormal

    INCOMPLETE
    • DTC judgment not completed
    • Perform driving pattern after confirming DTC enabling conditions

    N/A
    • Unable to perform DTC judgment
    • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

    HINT:

    • If the judgment result shows NORMAL, the system is normal.
    • If the judgment result shows ABNORMAL, the system has a malfunction.
    • If the judgment result shows INCOMPLETE or N/A, perform the normal judgment procedure again.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Perform the universal trip to clear permanent DTCs.

    Click here

  • Perform registration and/or initialization when parts related to the automatic transaxle are replaced.

    Click here

DATA LIST

NOTICE:

In the table below, the values listed under "Normal Condition" are reference values. Do not depend solely on these reference values when deciding whether a part is faulty or not.

HINT:

Using the Techstream to read the Data List allows the values or states of switches, sensors, actuators and other items to be read without removing any parts. This non-intrusive inspection can be very useful because intermittent conditions or signals may be discovered before parts or wiring is disturbed. Reading the Data List information early in troubleshooting is one way to save diagnostic time.

(a) Warm up the engine.

(b) Turn the engine switch off.

(c) Connect the Techstream to the DLC3.

(d) Turn the engine switch on (IG).

(e) Turn the Techstream on.

(f) Enter the following menus: Powertrain / Transmission / Data List / Stop Light SW.

(g) Read the Data List according to the display on the Techstream.

Powertrain > Transmission > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Stop Light SW

Stop light switch status

ON or OFF
  • ON: Brake pedal depressed
  • OFF: Brake pedal released

-
Powertrain > Transmission > Data List

Tester Display

Stop Light SW

PROCEDURE

1.

READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Transmission / Data List / Stop Light SW.

(e) Read the Data List according to the display on the Techstream.

Powertrain > Transmission > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Stop Light SW

Stop light switch status

ON or OFF
  • ON: Brake pedal depressed
  • OFF: Brake pedal released
 
Powertrain > Transmission > Data List

Tester Display

Stop Light SW

Result

Proceed to

Data List value is normal

A

Data List value is not normal

B
A

SYMPTOM SIMULATION AND DTC CHECK

B

2.

CHECK STOP LIGHT SWITCH ASSEMBLY INSTALLATION

(a) Check the stop light switch assembly installation condition.

Click here

OK:

Stop light switch assembly is installed correctly.

NG

REINSTALL STOP LIGHT SWITCH ASSEMBLY CORRECTLY

OK

3.

INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Inspect the stop light switch assembly.

Click here

NG

REPLACE STOP LIGHT SWITCH ASSEMBLY

OK

4.

CHECK TERMINAL VOLTAGE (STP VOLTAGE)

(a) Disconnect the A37 ECM connector.

*a

Brake pedal depressed

*b

Brake pedal released

*c

Front view of wire harness connector

(to ECM)

-

-

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A37-27 (STP) - Body ground

Brake pedal released

Below 1.5 V

Brake pedal depressed

7.5 to 14 V

HINT:

If there is a short in the STP terminal circuit, there may be a malfunction in the circuit of a connected ECU.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM)
OK

5.

REPLACE ECM

(a) Replace the ECM.

Click here

NEXT

PERFORM A/T CODE REGISTRATION

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    Transmission Range Sensor "A" Circuit Open (P070513,P070562)
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