Test 32A - Brake Switch Circuit (Code 81)

Test 32A: Repairing Code (81) Brake Switch Circuit (Part 1 Of 2):

Test 32A: Repairing Code (81) Brake Switch Circuit (Part 2 Of 2):

NOTE: When connecting or disconnecting connectors and inspecting connectors clean and repair as necessary.

NOTE: After completion of a repair or test then perform Verification Test. Verification Test VER-1A - ABS

NAME OF CODE:
Brake Switch Circuit

SET CONDITION:
The following criteria must be met for this code to be detected.
1. Brake switch signal continuously high.
2. Vehicle speed greater than 10 mph for 10 seconds after the end of a self test.

THEORY OF OPERATION:
One of the inputs to the EBC-5H Controller Antilock Brake (CAB) is a switch whose output is normally low and which goes high when the brake pedal is depressed. A check on the integrity of this signal begins when the self test ends. The state of the brake switch signal is examined once every 5 ms. The first time the signal appears low before satisfying set condition 2, the brake pedal switch check is ended and subsequent antilock activity is enabled. If the pedal switch signal stays high continuously until a total of 10 seconds has accumulated at a vehicle speed exceeding 10 mph, (81) Brake Switch Circuit Failure is set.

POSSIBLE CAUSES:
- Malfunctioning or misadjusted brake switch (12v)
- Brake switch circuit shorted to battery (12v) inside the CAB
- Brake pedal continuously depressed
- 0pen ground connection to service brake switch

Controller-Antilock Brake Connector: