Toyota Avalon (XX50): Brake Override System. Check For Intermittent Problems. Check Mode Procedure

Brake Override System

DESCRIPTION

When the vehicle is being driven, depressing the accelerator pedal sensor assembly and brake pedal will activate the brake override system to restrict driving torque. The conditions for activating the brake override system as well as the items that are controlled are explained below.

• When the accelerator pedal and brake pedal are depressed.

  NOTICE:

  The vehicle may not enter the brake override system control due to the relation of the accelerator pedal angle and the vehicle's speed.

• When the vehicle speed is extremely low, the accelerator opening value used when controlling the engine is reduced more than normal.

  HINT:

  During control, the Accelerator Position value in the Data List will be lower than normal.

• When the vehicle speed is not extremely low, the accelerator opening value is forcibly lowered to a fixed value.

  HINT:

  • During control, the Accelerator Position value in the Data List is forcibly reduced to a specified value regardless of the actual accelerator opening value (Accelerator Position Sensor No.1 Voltage %).
  • During brake override system control, the operation indicator is displayed on the meter.

• When the brake pedal or the accelerator pedal returns to some degree.

CAUTION / NOTICE / HINT

Example:

Drive at 10 km/h (6.25 mph), depress the accelerator pedal by 1/2 to 3/4 and keep it in that position. Under these conditions, if the engine speed decreases to 1000 rpm when the brake pedal is depressed, then the brake override system has been activated.

CAUTION:

When carrying out the inspection, use a place where you are able to carry it out safely and also pay close attention to your surroundings.

Also, when driving make absolutely sure that all road traffic laws, such as speed limits, are observed.

HINT:

• Under normal conditions, the Accelerator Position value changes in response to the Accelerator Position Sensor No.1 Voltage % value. For more information on the numerical values, refer to the Data List.

  Click here

• If the Accelerator Position and Accelerator Position Sensor No.1 Voltage % values in the Data List diverge and the Accelerator Position value in the Data List is fixed even though Accelerator Position Sensor No.1 Voltage % is changing, check that this control is activated (use the Techstream data saving function to record data while driving the vehicle and then confirm it after driving is completed).

NOTICE:

The brake override system restricts driving torque if the brake pedal is depressed when driving with the accelerator pedal depressed. If a customer reports experiencing loss of torque after the accelerator and brake pedals have both been intentionally depressed, explain to the customer that this is not a malfunction, and that the customer should avoid depressing both the accelerator and brake pedals at the same time.

Example: While operating the accelerator pedal, the customer uses their left foot to operate the brake pedal.

PROCEDURE

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Enter the following menus: System Select / Health Check.

(d) Check the DTCs.

B

GO TO DTC CHART

A

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Enter the following menus: Chassis / ABS/VSC/TRAC/EPB / Data List / Master Cylinder Sensor.

(d) Read the value displayed on the Techstream.

(e) Check that the brake fluid pressure value of the "Master Cylinder Sensor" observed on the Techstream changes when the brake pedal is depressed.

OK:

When the pedal is depressed, the pressure displayed on the Techstream increases.

NG

CHECK BRAKE ACTUATOR ASSEMBLY

OK

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Enter the following menus: Powertrain / Engine / Data List / Stop Light SW.

(d) Check the Data List indication when the brake pedal is depressed and released.

OK:

NG

INSPECT STOP LIGHT SWITCH ASSEMBLY

OK

(a) Inspect and adjust the brake pedal support assembly.

Click here

HINT:

If the stop light switch turns ON too late, the start of brake override system control may be delayed; if it turns ON too soon, brake override system control may begin too early, so conduct inspection of the brake pedal support assembly and stop light switch assembly.

NG

REPAIR OR REPLACE BRAKE PEDAL SUPPORT ASSEMBLY

OK

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Enter the following menus: Powertrain / Engine / Data List / Accelerator Position Sensor No.1 Voltage % and Accelerator Position Sensor No.2 Voltage %.

(d) Read the value displayed on the Techstream.

OK:

HINT:

For numerical values of Accelerator Position Sensor No.1 Voltage % and Accelerator Position Sensor No.2 Voltage %, refer to the Data List.

Click here

NG

REPLACE ACCELERATOR PEDAL SENSOR ASSEMBLY

OK

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Start the engine.

(d) Enter the following menus: Powertrain / Engine / Data List / Vehicle Speed.

(e) Read the value displayed on the Techstream.

Standard:

CAUTION:

When performing a drive test, obey all speed limits and traffic laws.

HINT:

Data can be captured relatively easily by using the snapshot function in the Data List. Confirm the data after performing the drive test.

NG

GO TO METER / GAUGE SYSTEM (SPEED SIGNAL CIRCUIT)

OK

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG) and turn the Techstream on.

(c) Start the engine.

(d) Enter the following menus: Chassis / ABS/VSC/TRAC/EPB / Data List / FR Wheel Speed, FL Wheel Speed, RR Wheel Speed and RL Wheel Speed.

(e) Read the value displayed on the Techstream.

Standard:

CAUTION:

When performing a drive test, obey all speed limits and traffic laws.

HINT:

Data can be captured relatively easily by using the snapshot function in the Data List. Confirm the data after performing the drive test.

OK

END

NG

INSPECT FRONT OR REAR SPEED SENSOR

Check For Intermittent Problems

CHECK FOR INTERMITTENT PROBLEMS

HINT:

Inspect the vehicle ECM using check mode. Intermittent problems are easier to detect with the Techstream when the ECM is in check mode. In check mode, the ECM uses 1 trip detection logic, which is more sensitive to malfunctions than normal mode (default), which uses 2 trip detection logic.

1. Clear the DTCs.

   Click here

2. Switch the ECM from normal mode to check mode using the Techstream.

   Click here

3. Perform a simulation test.

   Click here

4. Check and wiggle the harness(es), connector(s) and terminal(s).

   Click here

Check Mode Procedure

CHECK MODE PROCEDURE

HINT:

Compared to normal mode, check mode is more sensitive to malfunctions. Therefore, check mode can detect malfunctions that cannot be detected in normal mode.

NOTICE:

All the stored DTCs and freeze frame data are cleared if: 1) the ECM is changed from normal mode to check mode or vice versa; or 2) the engine switch is turned from on (IG) to ACC or off while in check mode. Before changing modes, always check and note any DTCs and freeze frame data.

CHECK MODE PROCEDURE

(a) Check and ensure the following conditions:

(1) Battery voltage is 11 V or higher.

(2) Throttle valve is fully closed.

(3) Shift lever is in P or N.

(4) A/C switch is off.

(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 / Engine / Utility / Check Mode.

(g) Switch the ECM from normal mode to check mode.

(h) Check that the MIL flashes as shown in the illustration.

(i) Start the engine.

(j) Check that the MIL turns off.

(k) Simulate the conditions of the malfunction described by the customer.

(l) Check the DTCs and freeze frame data using the Techstream.