Dtc P0504 Brake Switch A / B Correlation
Lexus IS250 IS220d GSE20 ALE20 2AD-FHV ENGINE CONTROL SYSTEM
DESCRIPTION
WIRING DIAGRAM
INSPECTION PROCEDURE
CHECK STOP LIGHT CIRCUIT
READ VALUE OF INTELLIGENT TESTER (STP SIGNAL)
CHECK STOP LIGHT SWITCH ASSEMBLY
CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - ECM)
DTC P0504 Brake Switch "A" / "B" Correlation
DESCRIPTION
In this system, the signals of the duplex type stop light switch (STP and ST1-) are used to judge whether the brake system is abnormal. When signals that indicate depressing and releasing the brake pedal are detected simultaneously, the ECM interprets this as a malfunction of the stop light switch.
- Normal conditions are shown in the table below.
| 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 is ON (IG)
(b) Brake pedal is released
(c) STP signal is OFF when ST1- signal is OFF |
Short in stop light switch signal circuit
Stop light switch
ECM
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WIRING DIAGRAM
INSPECTION PROCEDURE
- After replacing the ECM, the new ECM needs registration and initialization .
| 1.CHECK STOP LIGHT CIRCUIT |
Check if the stop lights turn ON and OFF when the brake pedal is depressed and released.
- OK:
- Stop lights turn ON and OFF normally.
| | REPAIR OR REPLACE STOP LIGHT SWITCH CIRCUIT |
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| 2.READ VALUE OF INTELLIGENT TESTER (STP SIGNAL) |
Connect the intelligent tester to the DLC3.
Turn the engine switch ON (IG) and turn the intelligent tester ON.
Enter the following menus: Powertrain / Engine / Data List / Stop Light Switch.
Check the result.
- OK:
| Brake Pedal | Specified Condition |
| Depressed | STP signal ON |
| Released | STP signal OFF |
| | CHECK FOR INTERMITTENT PROBLEMS |
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| 3.CHECK STOP LIGHT SWITCH ASSEMBLY |
Remove the stop light switch.
Measure the resistance of the switch.
- Standard resistance:
| Tester Connection | Switch Condition | Specified Condition |
| 1 - 2 | Pin not pushed | Below 1 Ω |
| 3 - 4 | Pin not pushed | 10 kΩ or higher |
| 1 - 2 | Pin pushed | 10 kΩ or higher |
| 3 - 4 | Pin pushed | Below 1 Ω |
| | REPLACE STOP LIGHT SWITCH ASSEMBLY |
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| 4.CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - ECM) |
Disconnect the A22 stop light switch connector.
Disconnect the A49 ECM connector.
Measure the resistance of the wire harness side connectors.
- Standard resistance:
| Tester Connection | Specified Condition |
| A22-1 - STP (A49-35) | Below 1 Ω |
| A22-4 - ST1- (A49-34) | Below 1 Ω |
| A22-1 or STP (A49-35) - Body ground | 10 kΩ or higher |
| A22-4 or ST1- (A49-34) - Body ground | 10 kΩ or higher |
| | REPAIR OR REPLACE HARNESS OR CONNECTOR |
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LEXUS IS250, IS220d / GSE20 ALE20
