31
SECTION H - TROUBLESHOOTING ABS MODULATORS
A
B
C
Electrical connector on the
M-30T
™
modulator-valve.
Make repairs to wiring or replace
ABS modulator-valve. Reconnect all
connectors to the MC-30
™
controller
and M-30T
™
modulator-valve. Reset
fault codes by briefl y holding a magnet
in place at the RESET location of the
diagnostic display. Then rerun the
power up sequence.
Go to Section A.
MOD LED and ABS indicator lamp
are on.
Turn off power to the MC-30
™
controller
and remove the 30-pin connector.
Static ABS Modulator Faults
-
Verify 7.0 to 10.0 OHMS across Hold
and Common connector pins. Verify
7.0 to 10.0 OHMS across Exhaust/
Common connector pins. Verify 14.0
to 20.0 OHMS across Exhaust/Hold
connector pins. Verify no continuity
from modulator connector pins to
ground. Verify ignition power is not
measured at any modulator connector
pins. Check for corroded or damaged
modulator wiring and connections.
If a circuit fault is found, isolate the
area needing repair by repeating the
measurements at all connections in
the ABS modulator circuit.
ABS modulator fault identifi ed?
Dynamic ABS Modulator Faults
- Verify proper modulator-valve
activation with brake pressure applied,
at power-up (Chuff Test) and/or using
diagnostic tool. The wiring to the
modulator may be reversed. Check
for dragging brakes, dry bearings,
faulty return springs, parking brake
system faults, restricted brake air
lines, over adjusted slacks, out of
round drums or damaged/loose tone
rings.
Make repairs to ABS modulator-
valve installation or wheel end.
Reconnect all connectors to the
MC-30
™
controller and M-30T
™
modulator-valve. Reset fault codes
by briefl y holding a magnet in place at
the RESET location of the diagnostic
display. Then rerun the power up
sequence.
Go to Section A.
NO
YES
1
2
3
J2 Modulator 1 Hold
H3 Modulator 1 Common
J3 Modulator 1 Exhaust
H2 Modulator 2 Hold
J1 Modulator 2 Common
K1 Modulator 2 Exhaust
K J H G F E D C B A
30-Pin Connector
E1 Ignition
Power
E3 Brake Light Power
D2 Ground
Hold Common Exhaust
