Home › Engine/Hybrid System › Engine Control › 3UR-FE ENGINE CONTROL: SFI SYSTEM
Last Modified: 11-27-2007 1.6 C
Service Category: Engine/Hybrid System Section: Engine Control
Model Year: 2008 Model: LX570 Doc ID: RM000000XCT04TX
Title: 3UR-FE ENGINE CONTROL: SFI SYSTEM: DESCRIPTION (2008 LX570)

DTC

P0504

Brake Switch "A" / "B" Correlation

DESCRIPTION

The stop light switch is a duplex system that transmits two signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed and released, are detected simultaneously, the ECM interprets this as a malfunction in the stop light switch and stores the DTC.

HINT:

The normal conditions are as shown in the table below. The signals can be read using the Techstream.

Signal

Brake Pedal Released

In Transition

Brake Pedal Depressed

STP

OFF

ON

ON

ST1-

ON

ON

OFF

DTC Code

DTC Detection Condition

Trouble Area

P0504

Conditions (a), (b) and (c) continue for 0.5 seconds or more (1 trip detection logic):

(a) The engine switch is on (IG).

(b) The brake pedal is released.

(c) The STP signal is OFF when the ST1- signal is OFF.
  • Short in stop light switch signal circuit
  • STOP fuse
  • IGN fuse
  • Stop light switch
  • ECM

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

  • Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
  • STP signal conditions can be checked using the Techstream.
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Stop Light Switch.
    5. Check the STP signal when the brake pedal is depressed and released.

Brake Pedal Operation

Specified Condition

Depressed

STP signal ON

Released

STP signal OFF

PROCEDURE

1.

CHECK STOP LIGHT SWITCH ASSEMBLY (B+ VOLTAGE)


(a) Disconnect the A30 stop light switch connector.

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

A30-2 - Body ground

Always

11 to 14 V

A30-3 - Body ground

Engine switch on (IG)

11 to 14 V
OK

2.

INSPECT STOP LIGHT SWITCH ASSEMBLY


(a) Remove the stop light switch.

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

Standard Resistance:

Tester Connection

Switch Condition

Specified Condition

1 - 2

Pin not pushed

Below 1 Ω

Pin pushed

10 kΩ or higher

3 - 4

Pin not pushed

10 kΩ or higher

Pin pushed

Below 1 Ω
OK

3.

CHECK ECM (STP, ST1- VOLTAGE)


(a) Disconnect the A38 ECM connector.

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

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A38-35 (ST1-) - Body ground

Brake pedal released

11 to 14 V

Brake pedal depressed

0 to 3 V

A38-36 (STP) - Body ground

Brake pedal released

0 to 3 V

Brake pedal depressed

11 to 14 V
OK

4.

INSPECT FUSE (STOP AND IGN)


(a) Remove the STOP and IGN fuses from the engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

STOP fuse

Always

Below 1 Ω

IGN fuse

Always

Below 1 Ω
OK