Knorr-Bremse Group
11
Doc. No. Y250910 (EN - Rev. 001)
September 2016
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KB4TA / KB4TA D System Diagnostics
C o m m e r c i a l V e h i c l e S y s t e m s
PD-203-390
Chart 6
Troubleshooting the Modulator Relay Valve (BR9234, K019290 and K019299)
NO
YES
External ABS Modulator DTCs:
Turn off the power to the module, disconnect the 12-
pin ECU connector
Static ABS Modulator DTCs:
Verify/Inspect the following:
–
13 to 17 Ohms across Exhaust/Common connector
pins.
–
No continuity from modulator connector pins to
ground.
–
Vbat is not measured at any modulator connector
pins.
–
Modulator/ECU wiring and connectors are not
damaged or corroded.
If an issue with the wiring is found, isolate the area
needing correction by repeating the measurements at
all connections.
Issue with modulator relay valve circuit identified?
Make corrections as needed (replace
wiring and/or ABS components).
Reconnect all connectors to the module.
Then rerun the power-up sequence .
Dynamic ABS Modulator DTCs:
Verify/Inspect the following:
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 slack adjusters
–
out-of-round drums
–
damaged/loose sensing rings
12 11 10
9
8
7
KB4TA Module - X1 Connector
Pin 1 AUXI01
(Valve 3rd Modulator)
Pin 12 AUXRET1 (Return Line
3rd Modulator)
1
4
3
2
3rd Modulator Connector Pins
Pin 1 AUXI01 (Exhaust Solenoid)
Pin 2 AUXRET1 (Common - GND)
KB4TA
12 11 10
9
8
7
X2 Connector
Pin 3 MV1 (SL side Modulator)
Pin 4 MV2 (SR side Modulator)
Pin 9 LSS1 (GND SL & SR
Modulators)
Pin 10 LSS1 (GND 3rd Modulator)
KB4TA D
1
4
3
2
SL, SR & 3rd Modulator Connector Pins
Pin 2 MV1, MV2 & 3rd Mod (Exhaust Solenoid)
Pin 3 LSS1
(Common - GND)
12 11 10
9
8
7
X1 Connector
Pin 1 AUXI01 (Valve 3rd Modulator)
12 11 10
9
8
7
12 11 10
9
8
7
X2 Connector
Pin 3 MV1
(SL side Modulator)
Pin 4 MV2
(SR side Modulator)
Pin 9 LSS1
(GND Modulator)
X1 Connector
Pin 1 AUXI01
(Valve 3rd Modulator)
Pin 12 AUXRET1 (Return Line
3rd Modulator)
K140786
K068353 & K146282
Y026787: 006: EN: Released: Fri Nov 11 11:18:50 CET 2016:
