
3 Diagnostics, Troubleshooting and Testing
22
Meritor WABCO Maintenance Manual MM-0112 (Revised 05-13)
Figure 3.14
Modulator Valve Testing
Electrical Checks
앫 Check modulator valve by itself for resistance. Figure 3.15 and
Figure 3.16.
앫 Check ECU harness and modulator valve together for resistance.
Figure 3.17 and Figure 3.18.
앫 Verify no change in resistance or open circuit between valve by
itself and through harness.
앫 Check harness by itself for any shorts to battery and shorts to
ground.
앫 Measurements should read as follows:
Figure 3.14
4007204a
FRAME MOUNT ECU WITHOUT ESC:
LOOKING INTO WIRE
HARNESS CONNECTOR
FRAME MOUNT ECU WITH ESC:
LOOKING INTO WIRE
HARNESS CONNECTOR
12
3456
710129118
12
3456
710129118
X1-GRAY X2-BLACK
X4-BROWN
(ONLY FOR 6 CHANNEL)
X4-BROWN
(ONLY FOR 6 CHANNEL)
X3-GREEN
12
3456
71012 911 8
123456
710129118
12
3456
710129118
12
3456
710129118
12
3456
710129118
X1-BLACK
X3-GREEN
131618 1517 14
12
3456
71012 911 8
131618 1517 14
X2-GREEN
ECU Sensor Connector Pins
Cab-Mounted
Universal with ESC,
Universal or Basic
LF X2-18 pin 12 and 15
RF X2-18 pin 10 and 13
LR X2-18 pin 11 and 14
RR X2-18 pin 17 and 18
LR (3rd axle) X3-15 pin 2 and 5
RR (3rd axle) X3-15 pin 11 and 14
Frame-Mounted
Non-ESC
LF X2-Black 7 and 8
RF X2-Black 5 and 6
LR X3-Green 1 and 2
RR X3-Green 3 and 4
LR (3rd axle) X4-Brown 3 and 4
RR (3rd axle) X4-Brown 5 and 6
Frame-Mounted
With ESC
LF X2-Green 17 and 18
RF X2-Green 5 and 6
LR X3-Green 1 and 2
RR X3-Green 3 and 4
LR (3rd axle) X4-Brown 3 and 4
RR (3rd axle) X4-Brown 5 and 6
Location Measurement
Inlet valve pin to Ground 4.0-9.0 ohm for 12V system
11.0-21.0 ohm for 24V system
Outlet valve pin to Ground 4.0-9.0 ohm for 12V system
11.0-21.0 ohm for 24V system
At ECU harness pins with
modulator valve connected
Same as above, no more than 1
ohm difference
ECU harness by itself for battery
voltage or ground
No continuity
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