1, 2 and 3 Digit Codes: 13

Fault Code 13 Diagnosis Chart:

Hydraulic Assembly Plausibility Switches Circuit:

CONTROL PRESSURE SWITCH-S1 OPERATION
The ABCM provides the control pressure switch circuit (circuit PT2 ABCM pin 16) 5 volts at all times. When the brakes are not applied, S1 is closed, completing a path to ground for circuit PT2 and holding ABCM pin 16 at 0 volts ground.

When the brakes are applied enough to generate approximately 400 psi in the booster circuit, S1 opens, removing the path to ground and forcing circuit PT2 to 5 volts. The ABCM monitors voltage on pin 16 to determine the position of the control pressure switch.

SWITCH SEQUENCE
When normal brake application apply is made, the following sequence of events should take place:
1. As soon as the pedal is depressed, the brake light switch should close, providing a 12 volt signal to ABCM pin 25.
2. As the booster piston continues to move, switch S2A opens, forcing ABCM pin 31 to 2.5 volts.
3. As the brake is applied further, the control pressure switch (S1) opens, holding ABCM pin 16 at 5 volts.
4. As full pedal travel is reached, switch S2B opens forcing ABCM pin 31 to 5 volts.

FAILURE CONDITIONS
ABCM Codes 13, 14, and 15 will set if an improper switch sequence is detected. The specific conditions required to set each code are as follows:

Code 13 - S2B opens before S1.
Code 14 - S1 opens before S2A.
Code 15 - S1 opens before BLS closes or S2B opens before BLS closes.

Air in the brake system will sometimes cause Fault Codes 13, 14 or 15 to set due to additional booster piston travel requirements.