Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual — part 38
4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS
6E–147
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The ECM is calculates an injection quantity and an
injection timing using the various sensors. And the PSG
controls the high pressure solenoid valve depending on
programmed pump map data.
The signal of desired injection quantity and actual injec-
tion quantify are exchanged via the CAN-bus between
the PSG and ECM.
If the relation of engine speed signal and doubled pump
camshaft speed signal excessively large, DTC P0251
(Symptom Code 7) will be stored.
If the CAN high or low circuit is defected, DTC P0251
(Symptom Code E) will be stored.
Diagnostic Aids
An intermittent may be caused by the following:
• Poor connections.
• Misrouted harness.
• Rubbed through wire insulation.
• Broken wire inside the insulation.
Check for the following conditions:
• Poor connection at ECM and PSG-Inspect harness
connectors for backed out terminals, improper
mating, broken locks, improperly formed or damaged
terminals, and poor terminal to wire connection.
• Damaged harness-Inspect the wiring harness for
damage. If the harness appears to be OK, observe
the “Injection Quantity” display on the Tech2 while
moving connectors and wiring harness related to the
sensor.
Diagnostic Trouble Code (DTC) P0251 (Symptom Code 6) (Flash Code 53)
Injection Pump Malfunction
Flash
Code
Code
Symptom
Code
MIL
DTC Name
DTC Setting Condition
Fail-Safe (Back Up)
53
P0251
6
ON
Injection Pump Malfunction
1. No pump camshaft speed
sensor error.
2. High pressure solenoid
valve control pulse width
does not match with
desired fuel injection quan-
tity.
1. MAB (fuel cutoff solenoid
valve) is operated.
2. Desired injection quantity
becomes 0mg/strk.
7
ON
Injection Pump Malfunction
1. No pump camshaft speed
sensor error.
2. No CKP sensor error.
3. Difference of engine speed
and doubled pump cam-
shaft speed is more than
720rpm (4JA1-TC) or
690rpm (4JH1-TC).
9
ON
Injection Pump Malfunction
No pump map programmed in
the PSG (pump control unit)
or PSG malfunction.
A
ON
Injection Pump Malfunction
EEPROM or A/D converter
malfunction in the PSG (pump
control unit).
Fuel injection quantity is
reduced.
B
ON
Injection Pump Malfunction
PSG (pump control unit) rec-
ognized high pressure sole-
noid valve drive circuit error.
No fail-safe function.
D
ON
Injection Pump Malfunction
PSG (pump control unit) could
not measure the high pres-
sure solenoid valve drive volt-
age.
E
ON
Injection Pump Malfunction
ECM could not accept PSG
(pump control unit) message.
1. MAB (fuel cutoff solenoid
valve) is operated.
2. Desired injection quantity
becomes 0mg/strk.
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to Step 2
Go to On Board
Diagnostic
(OBD) System
Check
6E–148
4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS
2
1. Connect the Tech 2.
2. Review and record the failure information.
3. Select “F0: Read DTC Infor As Stored By ECU” in
“F0: Diagnostic Trouble Codes”.
Is the DTC P0251 (Symptom Code 6) stored as
“Present Failure”?
—
Go to Step 3
Refer to
Diagnostic Aids
and Go to Step
3
3
1. Using the Tech 2, ignition “On” and engine “Off”.
2. Select “F1: Clear DTC Information” in “F0:
Diagnostic Trouble Codes” with the Tech 2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F0: Read
DTC Infor As Stored By ECU” in the “F0:
Diagnostic Trouble Codes”.
Was the DTC P0251 (Symptom Code 6) stored in this
ignition cycle?
—
Go to Step 4
Refer to
Diagnostic Aids
4
Replace the injection pump assembly.
Is the action complete?
—
Verify repair
—
Step
Action
Value(s)
Yes
No
4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS
6E–149
Diagnostic Trouble Code (DTC) P0251 (Symptom Code 7) (Flash Code 53)
Injection Pump Malfunction
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to Step 2
Go to On Board
Diagnostic
(OBD) System
Check
2
1. Connect the Tech 2.
2. Review and record the failure information.
3. Select “F0: Read DTC Infor As Stored By ECU” in
“F0: Diagnostic Trouble Codes”.
Is the DTC P0251 (Symptom Code 7) stored as
“Present Failure”?
—
Go to Step 3
Refer to
Diagnostic Aids
and Go to Step
3
3
1. Using the Tech 2, ignition “On” and engine “Off”.
2. Select “F1: Clear DTC Information” in “F0:
Diagnostic Trouble Codes” with the Tech 2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F0: Read
DTC Infor As Stored By ECU” in the “F0:
Diagnostic Trouble Codes”.
Was the DTC P0251 (Symptom Code 7) stored in this
ignition cycle?
—
Go to Step 4
Refer to
Diagnostic Aids
and Go to Step
4
4
Was the DTC P0335 (Symptom Code B), P0335
(Symptom Code D) or P1335 (Symptom Code A)
stored at the same time?
—
Go to DTC
Chart P0335
(Symptom
Code B)
(Symptom
Code D) or
P1335
(Symptom
Code A)
Go to Step 5
5
Check for poor/faulty connection at the ECM or PSG
(pump control unit) connector. If a poor/faulty
connection is found, repair the faulty terminal.
Was the problem found?
—
Verify repair
Go to Step 6
91
8
C-57(B)
E-6
6E–150
4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS
6
If a oscilloscope is available, monitor the CKP sensor
output signal. Does the oscilloscope indicate correct
wave form?
—
Go to Step 13
Not available:
Go to Step 7
Fixed at low: Go
to Step 7
Fixed at High:
Go to Step 8
Step
Action
Value(s)
Yes
No
CKP Sensor Output Reference Wave Form
0V
→
Measurement Terminal: 91 (+) 1 (-)
Measurement Scale: 5.0V/div
2.0ms/div
Measurement Condition: Engine speed at 2000rpm
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