Hino 238, Workshop Manual

Page: 777 / 919

DEF SCR SYSTEM (DCU) 5–211
CHECKLIST: P20A1
DTC: P20A1 Reverting valve for DEF pump stuck close Inspection Procedure
Step Action Description Judgement
Check
(Yes/No)
Yes No
1
Check the
operation of
the DEF pump
(reverting
valve) [Hino-
DX]
Check the operating sound of the
reverting valve using [Activation
Test] on Hino-DX.
Set the starter switch to the "ON"
position, Select [Reverting valve]
from [Activation Test] and check
the operating sound of the revert-
ing valve.
Operation
sound was
able to be
heard: Go to
YES.
It was not
audible: Go to
NO.
Go to step 2.
Replace DEF
pump.
Perform "After-
inspection
work" of
INFORMA-
TION section.
2
Inspect the
DEF pump
(reverting
valve) [Hino-
DX]
Check the DEF pressure using
[Activation Test] and Data monitor
on Hino-DX
1. Select [DEF pump position]
from the [Activation Test]
menu and operate the DEF
pump.
2. Select [DEF pump pressure]
from the [Data Monitor]
menu and check the DEF
pressure.
<Standard values>
DEF pressure: less than 50 kPa
{7.3 psi}
The measure-
ments meet
the standard
value: Go to
YES.
The measure-
ments do not
meet the stan-
dard value: Go
to NO.
Go to step 3.
Replace DEF
pump.
Perform "After-
inspection
work" of
INFORMA-
TION section.
3
Inspect the
DEF tank
Check if the breather hose is not
disconnected, clogged, punctured
or cracked.
Failure found:
Go to YES.
No failure
found: Go to
NO.
Replace the
breather hose.
Perform "After-
inspection
work" of
INFORMA-
TION section.
Go to step 4.
4
Check the
DTC detected
(DCU) [Hino-
DX]
1. Start the engine and idle it
for 10 minutes while you
check if the DEF pressure is
maintained around 900 kPa
{131 psi} in [Data Monitor]
(800 kPa
–
1,050 kPa)
{(116 psi
–
152 psi)}.
2. Set the starter switch to the
"LOCK" position.
3. Check if the DCU main relay
is OFF in the Hino-DX
menu. (This cuts off the
communication between
Hino-DX and the DCU.)
4. Set the starter switch in the
"LOCK" position and turn it
the "ON" again.
5. Check if P20A1 has been
detected.
DTC P20A1
has been
detected: Go
to YES.
No DTC has
been detected:
Go to NO.
Replace the
DCU.
Perform "After-
inspection
work" of
INFORMA-
TION section. Procedure
completed.
Perform "After-
inspection
work" of
INFORMA-
TION section.