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. |
Signal (ECM Terminal) |
Brake Pedal Released | In Transition |
Brake Pedal Depressed | |
STP | OFF |
ON | ON | |
ST1- | ON |
ON | OFF |
- [OFF] denotes ground potential.
- [ON] denotes battery potential (+B).
- On the Techstream, both the Data List items Stop Light Switch and ST1
are ON when the brake pedal is depressed because the ST1 indication
characteristic is opposite to the Stop Light Switch indication.
|
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) Ignition switch ON (b) Brake pedal released (c) STP signal OFF when ST1- signal OFF |
- Short in stop light switch signal circuit
- STOP fuse
- IGN fuse
- Stop light switch
- ECM
| WIRING DIAGRAM
 CAUTION / NOTICE / HINT
NOTICE: Inspect the fuses of circuits related to this system before performing the following 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.
- Stop light switch conditions can be checked using the Techstream.
- Connect the Techstream to the DLC3.
- Turn the ignition switch to ON.
- Turn the Techstream on.
- Enter the following menus: Powertrain / Engine and ECT / Data List / Stop Light Switch and ST1.
- Check the Data List indication when the brake pedal is depressed and released.
|
Brake Pedal Operation | Stop Light Switch |
ST1 | | Depressed |
ON | ON | |
Released | OFF |
OFF | PROCEDURE
| 1. |
INSPECT STOP LIGHT SWITCH ASSEMBLY (B+ VOLTAGE) |
 (a) Disconnect the 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 | |
A4-2 - Body ground | Always |
11 to 14 V | |
A4-4 - Body ground | Ignition switch ON |
11 to 14 V |
| NG |
 | GO TO STEP 4 |
|
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 |
| NG |
| REPLACE STOP LIGHT SWITCH ASSEMBLY |
|
OK | |
| |
| 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 | |
A24-35 (ST1-) - Body ground |
Brake pedal released |
11 to 14 V | |
Brake pedal depressed |
0 to 3 V | |
A24-36 (STP) - Body ground |
Brake pedal released |
0 to 3 V | | Brake pedal depressed |
11 to 14 V |
| OK |
| REPLACE ECM |
| NG |
| REPAIR OR REPLACE HARNESS OR CONNECTOR |
| 4. |
INSPECT FUSES (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 |
| REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - STOP LIGHT SWITCH) |
| NG |
| CHECK FOR SHORTS IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE | | 
