Failure Code [Ca778] Engine Bkup Speed Sensor Error - Komatsu WA250-6 Shop Manual

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Failure code [CA778] Engine Bkup speed sensor error

Failure code

• Abnormality is detected in signals of engine Bkup speed sensor.

• Controls Bkup speed sensor with signals of Ne speed sensor.

• Turns the centralized warning lamp and alarm buzzer ON.

Problem that

• Starting performance is poor

• Engine output lowers.

• Method of reproducing failure code: Start engine

Defective sensor power sup-

ply 2 system

Defective engine Bkup

speed sensor

Broken engine Bkup speed

sensor or defective clear-

4 Broken rotation sensing ring Inspect it for breakage directly.

Disconnection in wiring har-

Possible causes

and standard

(Disconnection or defective

value in normal

contact in connector)

Ground fault in wiring har-

(Contact with ground circuit)

Hot short (Contact with 5V,

24V circuit) in wiring harness

Short circuit in wiring har-

(with another wiring harness)

330 Troubleshooting by failure code (Display of code), Part 3

Failure code [CA778] Engine Bkup speed sensor error

Engine Bkup speed sensor error

(Engine controller system)

Standard value in normal state/Remarks on troubleshooting

If failure code [CA187] is indicated simultaneously, carry out trouble-

shooting for it first.

a Prepare with starting switch OFF, then turn starting switch ON

and carry out troubleshooting.

Between (1) and (2)

Voltage is measured with wiring harness connected. Accordingly, if

voltage is abnormal, check wiring harness and controller, too, for

another cause of trouble, and then judge.

Inspect engine Bkup speed sensor directly for breakage or clear-

a Prepare with starting switch OFF, then carry out troubleshooting

without turning starting switch ON.