Troubleshooting Of Electrical System (E-Mode); Engine Does Not Start (Engine Does Not Crank) - Komatsu PC88MR-10 Shop Manual

40 Troubleshooting

Troubleshooting of electrical system (E-mode)

Troubleshooting of electrical system (E-mode)
E-1 Engine does not start (Engine does not crank)

Engine does not start (engine does not crank).

Failure
Engine starting circuit has following 2 start lock mechanisms.
1. Start lock by password protection of machine monitor
2. Start lock by lock lever position
Related
If failure symptom "Battery relay operation sound is not heard" appears when starting
information
switch is turned to ON position, perform troubleshooting for E-1 as well.
If failure symptom is "Machine monitor displays nothing" when starting switch is turned to
ON position, main electric power supply system may be defective. So, perform
troubleshooting for E-4 (lines connecting to fusible link F03 and fuse No. 17).
No. Cause
Loose terminal or open
1
circuit at terminal
Poor contact
(grounding) between
2
battery relay and frame
Insufficient battery
3
capacity
Defective engine
4
controller system
Defective fuse No. 3 in
5
fuse box F01
Defective battery relay
6
system
Defective fusible link
7 F02, defective wiring
harness
Defective starting
switch, lock lever
switch, starting motor
cut-off relay R06,
8
personal code relay
R07, battery relay, or
wiring harness
40-378
Procedure, measuring location, criteria, and remarks
1. Turn starting switch to OFF position.
Check terminals of starting motor, alternator, battery relay, and ground
terminals T09, T08, T12, etc.
1. Turn starting switch to OFF position.
Between battery relay terminal R01 and ground
a Use machine frame as grounding point for
Resistance
measurement.
a Loosened or rusted terminal T08
a Be ready with starting switch at OFF position, then perform
troubleshooting without turning starting switch to ON position.
Battery voltage (2 batteries)
Specific gravity of electrolyte (each
battery)
Defects of engine controller power supply and ACC signal are indicated with
failure codes [DB2QKR] and [DB2RKR]. If these codes appear, perform
troubleshooting for Causes 1 to 3 of [DB2QKR] first.
If fuse is burnt out, circuit probably has ground fault. (See Cause 21.)
1. Turn starting switch to ON position (to connect ACC).
a If battery relay operation sound is not heard, go to checks on Causes 19
and after.
1. Turn starting switch to OFF position, and remove fuse No. 3 in fuse box
F01.
2. Turn starting switch to ON position (to connect ACC).
Between input terminal (1A) of fuse box F01-3 and
Voltage
ground
a If voltage is abnormal, go to check on Cause 10.
1. Turn starting switch to OFF position.
2. Remove fuse No. 18 (30 A) of fuse box F01. (To prevent engine from
starting during troubleshooting)
3. Insert T-adapter into connector E12.
4. Turn starting switch to START position and hold it (two persons required
for this check).
Voltage Between E12 (1) and ground
a If voltage is abnormal, go to check on Cause 12 and after.
(ALL-3840-001-A-01-A)
(PC88MR-A21-400-A-Z0-A)
Max. 1 z
Min. 24 V
Min. 1.26
20 to 30 V
20 to 30 V
PC88MR-10