DESCRIPTION
The stop light switch is a duplex system that transmits 2 signals: STP and ST1-. These 2 signals are used by the ECM to monitor whether or not the brake system is working properly. If 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 signal conditions are as shown in the table below.
Signal (ECM Terminal) |
Brake Pedal Released |
In Transition |
Brake Pedal Depressed |
---|---|---|---|
STP |
OFF |
ON |
ON |
ST1- |
ON |
ON |
OFF |
DTC No. |
DTC Detection Condition |
Trouble Area |
---|---|---|
P0504 |
All of the following conditions continue for 0.5 seconds or more (1 trip detection logic): (a) The ignition switch is ON. (b) The STP signal is OFF when the ST1- signal is OFF. |
|
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.
HINT:
Brake Pedal Operation |
Stop Light Switch |
ST1 |
---|---|---|
Depressed |
ON |
ON |
Released |
OFF |
OFF |
PROCEDURE
1. |
INSPECT STOP LIGHT SWITCH ASSEMBLY (TERMINAL VOLTAGE) |
(a) Disconnect the stop light switch assembly connector. |
|
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
Tester Connection |
Switch Condition |
Specified Condition |
---|---|---|
A35-2 - Body ground |
Always |
11 to 14 V |
A35-4 - Body ground |
Ignition switch ON |
11 to 14 V |
*a |
Front view of wire harness connector (to Stop Light Switch Assembly) |
NG | ![]() |
REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
2. |
INSPECT STOP LIGHT SWITCH ASSEMBLY |
(a) Inspect the stop light switch assembly (See page
).
NG | ![]() |
REPLACE STOP LIGHT SWITCH ASSEMBLY |
|
3. |
INSPECT ECM (STP AND ST1- VOLTAGE) |
(a) Disconnect the ECM connector.
(b) Turn the ignition switch to ON.
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
Tester Connection |
Condition |
Specified Condition |
---|---|---|
A49-39 (ST1-) - Body ground |
Brake pedal released |
7.5 to 14 V |
Brake pedal depressed |
Below 1.5 V |
|
A49-29 (STP) - Body ground |
Brake pedal released |
Below 1.5 V |
Brake pedal depressed |
7.5 to 14 V |
*a |
Brake pedal depressed |
*b |
Brake pedal released |
*c |
Front view of wire harness connector (to ECM) |
- |
- |
OK | ![]() |
REPLACE ECM |
NG | ![]() |
REPAIR OR REPLACE HARNESS OR CONNECTOR |
Precaution
PRECAUTION
1. PRECAUTION FOR DISCONNECTING CABLE FROM NEGATIVE BATTERY TERMINAL
NOTICE:
After the ignition switch is turned off, the radio and display receiver
assembly records various types of memory and settings. As a result, after
turning ...
Problem Symptoms Table
PROBLEM SYMPTOMS TABLE
HINT:
Use the table below to help determine the cause of problem symptoms. If multiple
suspected areas are listed, the potential causes of the symptoms are listed in order
of probability in the "Suspected Area" column of ...
Precaution
PRECAUTION
1. PRECAUTION FOR DISCONNECTING CABLE FROM NEGATIVE BATTERY TERMINAL
NOTICE:
When disconnecting the cable from the negative (-) battery terminal, initialize
the following system after the terminal is reconnected:
System Name
...