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3. Spring brake not properly released manually.
4. Reduction of service system pressure causing spring brakes to partially apply.
5. Broken return spring in spring brake section (double diaphragm type).
(F) SERVICE BRAKES APPLY WHEN SPRING BRAKES ARE RELEASED BY AIR
1. Leaking push rod seal between spring brake and service section.
2. Improper plumbing.
(G) LEAK THRU SERVICE EXHAUST PORTS· SPRING BRAKES RELEASED BY AIR
1. Leaking push rod seal between spring brake and service section.
(H) SPRING BRAKE WILL NOT RELEASE (NORMAL OPERATION)
1. Insufficient air pressure.
2. Air leaks in spring brake air system.
3. Restrictions in spring brake air system.
4. Ruptured diaphragm and/or seal in spring brake section.
5. Broken spring causing malfunction.
(I) SPRING BRAKES CANNOT BE MECHANICALLY RELEASED
1. Release bolt stripped or broken.
2. Release bolt and wedged nut locked together.
Brakes
Note:
If the blink code indicated there are no faults, but the trailer ABS indicator lamp continues to come on
and stay on when you apply the brakes to the moving vehicle, there is an intermittent fault that must be
repaired. Refer to Maintenance Manual #33 "Expert Mode Diagnostics."
BRAKES WILL NOT RELEASE
Probable Cause Remedy
ABS Blink Code Diagnostic Guide A.B.S WABCO
0 No faults: System Okay. No action needed.
3 Sensor BU1: Cable break, short circuit or out of adjustment. Check sensor, sensor cable and
cable connection; adjust sensor; or check for excessive hub runout, a sensor gap that is too
wide or damaged to the tooth wheels.
4 Sensor YE1: Cable break, short circuit or out of adjustment. Check sensor, sensor cable and
cable connection; adjust sensor; or check for excessive hub runout, a sensor gap that is too
wade or damage to the tooth wheels.
5 Sensor BU2: Cable break, short circuit or out of adjustment. Check sensor, sensor cable and
cable connection; adjust sensor; or check for excessive hub runout, a sensor gap that is too
wide or damage to the tooth wheels.
6 Sensor YE2: Cable break, short circuit or out of adjustment. Check sensor, sensor cable and
cable connection; adjust sensor; or check for excessive hub runout, a sensor gap that is too
wide or damage to the tooth wheels.
7 Ext. Modulator (RD): Short to power, cable break or open, short to ground or cable damage,
or ECU/valve Assemble Failure. Check ABS valve and cable. Replace as required.
9 Ext. Modulator (BU): Short to power, cable break or open, short to ground or cable
damaged, or ECU/valve Assembly Failure. Check ABS valve and cable. Replace as required.
10 ECU/Valve Assemble Modulator (YE): Short to power, cable break or open, short to ground
or cable damaged, or ECU/Valve Assembly Failure. Check ABS valve and cable. Replace as
required.
14 Power Supply, ECU/Valve Assembly: Over or under voltage, current low, or internal failure.
Repair vehicle power supply, check vehicle voltage output and connector; check ECU's
configuration.
15 EMI Failure, ECU/Valve Assembly: Internal failure. Replace ECU.
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