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Trailer ABS Warning Lamp Troubleshooting

Symptom Possible Cause Action

Trailer ABS lamp

does not come on

when the ignition

is turned on.

There is no trailer connected or the trailer is not

equipped with PLC.

The trailer ABS lamp will not illuminate at start-up

unless a trailer equipped with PLC is connected to

the vehicle.

Trailers manufactured on or after March 1, 2001

are equipped with PLC.

The vehicle is not equipped with PLC. Verify that the vehicle has PLC.

Check the vehicle ABS ECU:

• WABCO E-Version ABS ECUs have PLC.

• Bendix ABS EC-30 ECUs have PLC unless

there is a label on it that says "ECU does

not control trailer ABS warning lamp."

• Eaton Gen 5 ABS ECU has PLC.

Check if vehicle was manufactured on or after

March 1, 2001.

The trailer ABS warning lamp bulb is burned-out. Replace the bulb.

There is a circuit fault between the tractor ABS

ECU and the trailer ABS warning lamp in the

dash.

Check and correct, if necessary.

The trailer ABS warning lamp circuit can be tested

at the tractor ABS ECU by grounding the pin to

that circuit. This should cause the lamp to illumi-

nate.

There is faulty wiring (power or ground). Check and correct as necessary.

The PLC ﬁlter is faulty. Check and replace as necessary.

The tractor ABS ECU is faulty. Be sure to check the trailer ABS lamp circuit and

try connecting vehicle to a trailer where PLC is

known to work. If the tractor ABS ECU is still

faulty, replace.

The trailer ABS ECU is faulty. Be sure to check the trailer ABS lamp circuit and

try connecting trailer to a vehicle where PLC is

known to work. If the trailer ABS ECU is still

faulty, replace.

Trailer ABS lamp

stays on.

There is a trailer ABS fault. Refer to the trailer ABS manufacturers literature

for troubleshooting. Repair as necessary.

Trailer ABS lamp circuit shorted to ground. Repair as necessary.

Table 18, Trailer ABS Warning Lamp Troubleshooting

Meritor WABCO Pneumatic Antilock Braking System

(ABS)

42.00

ABS System Troubleshooting

Business Class M2 Workshop Manual, Supplement 2, June 2002 300/19