51

DTC Code	DTC Name
51	Stop Light Switch Circuit Malfunction

DESCRIPTION

In this system, the signal of the stop light switch is used to judge whether the stop light system is abnormal or not.

The stop light switch has a duplex system (signals STP and ST1-) to memorize the abnormality when the signals of depressing and releasing the brake pedal are detected simultaneously.

Tech Tips

Normal condition is as shown in the table.

Signal	Brake pedal released	In transition	Brake pedal depressed
STP	OFF	ON	ON
ST1-	ON	ON	OFF

DTC No.	DTC Detection Condition	Trouble Area
51	When STP (without depressing the brake pedal) and ST1- (with the brake pedal depressed) signals continue for longer than 0.5 seconds with the ignition switch ON	Open or short in stop light switch signal circuit Stop light switch ECM

WIRING DIAGRAM

INSPECTION PROCEDURE

Tech Tips

Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

When using intelligent tester:

PROCEDURE

READ VALUE USING INTELLIGENT TESTER (STOP LIGHT SWITCH)

Connect the intelligent tester to the DLC3.
Turn the ignition switch ON.

Select the item "Powertrain/Engine and ECT/Data List/Stop Light SW" and read its value displayed on the intelligent tester.

OK

Brake Pedal	Display
Depressed	Stop Light SW ON
Repressed	Stop Light SW OFF

NG

INSPECT ECM Click here

OK

CHECK FOR INTERMITTENT PROBLEMS

INSPECT ECM

Turn the ignition switch ON.

Measure the voltage between the terminals of the ECM connector.

Standard voltage (Brake pedal is depressed)

Tester Connection	Specified Condition
STP (B10-19) - E1 (D2-14)	9 to 14 V
ST1- (B8-11) - E1 (D2-14)	Below 1.5 V

Standard voltage (Brake pedal is released)

Tester Connection	Specified Condition
STP (B10-19) - E1 (D2-14)	Below 1.5 V
ST1- (B8-11) - E1 (D2-14)	9 to 14 V

NG

INSPECT STOP LIGHT SWITCH Click here

OK

REPLACE ECM

INSPECT STOP LIGHT SWITCH

Disconnect the stop light switch connector.

Check the resistance between each pair of the terminals.

Standard resistance

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

NG

REPLACE STOP LIGHT SWITCH

OK

CHECK HARNESS AND CONNECTOR (ECM - STOP LIGHT SWITCH)

Disconnect the stop light switch connector.
Disconnect the ECM B8 and B10 connectors.

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

Standard resistance (Check for open)

Tester Connection	Specified Condition
(B2-1) - STP (B10-19)	Below 1 Ω
(B2-4) - ST1- (B8-11)	Below 1 Ω

Standard resistance (Check for short)

Tester Connection	Specified Condition
STP (B10-19) - Body ground	10 kΩ or higher
ST1- (B8-11) - Body ground	10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

REPAIR OR REPLACE POWER SOURCE CIRCUIT

When not using intelligent tester: