Lexus IS250 · Service Manual ENGINE

P0504

Diagnostic trouble codes

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 sets the DTC.

HINT:
The normal conditions are as shown in the table below. The signals can be read using an intelligent tester.
Signal
 Brake Pedal Released
 In Transition
 Brake Pedal Depressed
STP
 OFF
 ON
 ON
ST1-
 ON
 ON
 OFF

DTC No.
 DTC Detection Condition
 Trouble Area
P0504
 Conditions (a), (b) and (c) continue for 0.5 seconds or more
(1 trip detection logic):
(a) Engine switch on (IG)
(b) Brake pedal released
(c) STP signal OFF when ST1- signal OFF
  1. Short in stop light switch signal circuit
  2. Stop light switch
  3. ECM
P0724
 The stop light switch remains ON even when the vehicle is driven in a STOP (less than 3 km/h (2 mph)) and GO (30 km/h (19 mph) or more) fashion 5 times. (2 trip detection logic)
  1. Short in stop light switch signal circuit
  2. Stop light switch
  3. ECM

WIRING DIAGRAM

A122762E01

INSPECTION PROCEDURE

HINT:
Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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 (Click here).


1. CHECK STOP LIGHT (STOP LIGHT OPERATION)

  1. Check whether the stop lights turn on and off normally when the brake pedal is depressed and released.

    OK:
    Stop lights turn ON when brake pedal is depressed.



 NG
REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT
OK


2. READ VALUE OF INTELLIGENT TESTER (STP SIGNAL AND ST1 - VOLTAGE)

  1. A107724E04
    Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG) and turn the tester ON.

  1. Enter the following menus: Power train / Engine / Data List / Stop Light Switch.

  1. Check the STP signal when the brake pedal is depressed and released.

    OK:
    Brake Pedal Operation
    		 Specified Condition
    Depressed
    		 STP signal ON
    Released
    		 STP signal OFF

  1. Measure the voltage of the A5 and E4 ECM connectors.

    Standard voltage:
    Tester Connection
    		 Brake Pedal Operation
    		 Specified Condition
    ST1- (A5-8) - E1 (E4-7)
    		 Depressed
    		 Below 1.5 V
    ST1- (A5-8) - E1 (E4-7)
    		 Released
    		 7.5 to 14 V



OK
CHECK FOR INTERMITTENT PROBLEMS
NG


3. INSPECT STOP LIGHT SWITCH ASSEMBLY

  1. A107172E06
    Remove the stop light switch assembly.

  1. Measure the resistance of the stop light switch.

    Standard resistance:
    Switch Position
    		 Tester Connection
    		 Specified Condition
    Switch pin free
    		 1 - 2
    		 Below 1 Ω
    Switch pin free
    		 3 - 4
    		 10 kΩ or higher
    Switch pin pushed in
    		 1 - 2
    		 10 kΩ or higher
    Switch pin pushed in
    		 3 - 4
    		 Below 1 Ω

  1. Reinstall the stop light switch assembly.



 NG
REPLACE STOP LIGHT SWITCH ASSEMBLY
OK


4. CHECK ECM (STP, ST1 - VOLTAGE)

  1. A107725E04
    Disconnect the A5 and A6 ECM connectors.

  1. Measure the voltage of the A5 and A6 ECM connectors.

    Standard voltage:
    Tester Connection
    		 Brake Pedal Operation
    		 Specified Condition
    STP (A6-4) - Body ground
    		 Depressed
    		 9 to 14 V
    STP (A6-4) - Body ground
    		 Released
    		 0 to 3 V
    ST1- (A5-8) - Body ground
    		 Depressed
    		 0 to 3 V
    ST1- (A5-8) - Body ground
    		 Released
    		 9 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE ECM


← P0500P0505 →