P0724

A340E AUTOMATIC TRANSMISSION SYSTEM: P0724: Brake Switch "B" Circuit High

DTC P0724 - Brake Switch "B" Circuit High

DESCRIPTION

The purpose of this circuit is to prevent the engine from stalling while driving in lock-up condition when the brakes are suddenly applied.
When the brake pedal is depressed, this switch sends signals to the ECM. Then the ECM cancels the operation of the lock-up clutch while braking is in progress.





MONITOR DESCRIPTION

This DTC indicates that the stop light switch remains ON. When the stop light switch remains ON during STOP and GO driving, the ECM interprets this as a fault in the stop light switch, the MIL comes on and the ECM stores the DTC. The vehicle must STOP (less than 3 km/h (1.9 mph)) and GO (30 km/h (18.6 mph) or more) 5 times for 2 driving cycles, in order to detect a malfunction.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

The stop light switch remains ON during GO and STOP 5 times.
GO and STOP are defined as follows:





TYPICAL MALFUNCTION THRESHOLDS





WIRING DIAGRAM





INSPECTION PROCEDURE

1. DATA LIST

HINT: According to the Data List displayed by Techstream, you can read the values of switches, sensors, actuators and so on without removing parts. Reading the Data List as the first step of troubleshooting is one method to save time.

NOTE: In the table below, the values listed under "Normal Condition" are reference values. Do not depend solely on these reference values when deciding whether a part is faulty or not.

(a) Warm up the engine.
(b) Turn the ignition switch OFF.
(c) Connect Techstream to the DLC3.
(d) Turn the ignition switch ON, and turn the tester main switch ON.
(e) Enter the following menus: Powertrain / Engine and ECT / Data List.
(f) According to the display on the tester, read the "Data List".

Engine and ECT





PROCEDURE

1. INSPECT STOP LIGHT SWITCH ASSEMBLY





(a) Remove the stop light switch assembly.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:





NG -- REPLACE STOP LIGHT SWITCH ASSEMBLY
OK -- Continue to next step.
2. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM)





(a) Install the stop light switch assembly.
(b) Measure the voltage when the brake pedal is depressed and released.
Standard voltage:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM