2004 ISUZU TF SERIES Workshop Manual

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Page 1569 of 4264

ISUZU TF SERIES 2004 Workshop Manual 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–197
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The ECM is calculates an injection quantity and an
injection t

4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–197
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 ex changed via the CAN-bus between
the PSG and ECM.
If the relation of engine speed signal and doubled pump
camshaft speed signal ex cessively 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
CodeCode Symptom
CodeMIL DTC Name DTC Setting Condition Fail-Safe (Back Up)
53 P0251 6 ON Injection Pump Malfunction 1. No pump camshaft speed
se nsor erro r.
2. High pressure solenoid
v a lv e co ntro l pulse w idth
doe s no t ma tch 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
se nsor erro r.
2. No CKP senso r e rror.
3. Difference of engine speed
and doubled pump cam-
shaft speed is more than
720rpm (4JA1-TC) or 690
rpm (4JH1-TC).
9 ON Injection Pump Malfunction No pump map programmed in
the PSG (pump co ntrol unit)
or PSG malfunction.
A ON Injection Pump Malfunction EEPROM or A/D converter
malfunctio n in the PSG (pump
control unit).Fuel inje ctio n qua ntity is
reduced.
B ON Injection Pump Malfunction PSG (pump control unit) rec-
ognized high pressure sole -
noid valve drive circuit error.No fa il-sa fe fun ctio n.
D ON Injection Pump Malfunction PSG (pump control unit) could
no t me asure the high pres-
sure solenoid valve drive volt-
age.
E ON Injection Pump Malfunction ECM could not accept PSG
(pump co ntrol unit) messa ge.1. MAB (fuel cutoff solenoid
valve) is operated.
2. Desired injection quantity
becomes 0mg/strk.
Step Action Value(s) Yes No
1Was the “On-Board Diagnostic (OBD) System Check”
performed?
—Go to Step 2Go to On Board
Diagnostic
(OBD) System
Check

Page 1570 of 4264

ISUZU TF SERIES 2004 Workshop Manual 6E–198 4JA1/4JH1 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 T

Page 1571 of 4264

ISUZU TF SERIES 2004 Workshop Manual 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E –199
Diagnostic Trouble Code (DTC) P0251 (Symptom Code 7) (Flash Code 53)
Injection Pump Malfunction
Step Action Value(s) Yes No
1Was the “On-Bo

Page 1572 of 4264

ISUZU TF SERIES 2004 Workshop Manual 6E–200 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
6 If a oscilloscope is available, monitor the CKP sensor
output signal. Does the oscilloscope indicate correct
wav e form?
—Go to Step 13Not ava

Page 1573 of 4264

ISUZU TF SERIES 2004 Workshop Manual 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E –201
7 Using the DVM and check the CKP sensor output
circuit.
Breaker box is available:
1. Ignition “Off ”, engine “Off ”.
2. Install

Page 1574 of 4264

ISUZU TF SERIES 2004 Workshop Manual 6E–202 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
9 Check any accessory parts which may cause electric
interference or magnetic interference.
Was the problem found?—Remove the
accessory parts

Page 1575 of 4264

ISUZU TF SERIES 2004 Workshop Manual 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS 6E–203
Diagnostic Trouble Code (DTC) P0251 (Symptom Code 9) (Flash Code 53)
Injection Pump Malfunction
Step Action Value(s) Yes No
1Was the “On-Board D

Page 1576 of 4264

ISUZU TF SERIES 2004 Workshop Manual 6E–204 4JA1/4JH1 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0251 (Symptom Code A) (Flash Code 53)
Injection Pump Malfunction
Step Action Value(s) Yes No
1Was the “On-Board D

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