Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 133

6E–136

4JH1 ENGINE DRIVEABILITY AND EMISSIONS

7

Remove the eye bolt with gauze filter from the
injection pump and check for the following conditions. 

• Objects blocking at the gauze filter. Check for a

condition that causes contaminated fuel, such as
the customer is using an aftermarket fuel filter or
extended maintenance interval. 

• Check for a condition that causes fuel waxing or

icing, such as the customer is using an incorrect
fuel type in winter season or water mixed with the
fuel. 

If a problem is found, repair as necessary. 
Was the problem found?

—

Replace the eye 

bolt with gauze 

filter and verify 

repair

Go to Step 8

8

Replace the injection pump assembly. 
Is the action complete?

—

Verify repair

—

Step

Action

Value(s)

Yes

No

4JH1 ENGINE DRIVEABILITY AND EMISSIONS

6E–137

DIAGNOSTIC TROUBLE CODE (DTC) P0251 (SYMPTOM CODE 6) 

(FLASH CODE 53) INJECTION PUMP MALFUNCTION

DIAGNOSTIC TROUBLE CODE (DTC) P0251 (SYMPTOM CODE 7) 

(FLASH CODE 53) INJECTION PUMP MALFUNCTION

DIAGNOSTIC TROUBLE CODE (DTC) P0251 (SYMPTOM CODE 9) 

(FLASH CODE 53) INJECTION PUMP MALFUNCTION

DIAGNOSTIC TROUBLE CODE (DTC) P0251 (SYMPTOM CODE A) 

(FLASH CODE 53) INJECTION PUMP MALFUNCTION

DIAGNOSTIC TROUBLE CODE (DTC) P0251 (SYMPTOM CODE B) 

(FLASH CODE 53) INJECTION PUMP MALFUNCTION

DIAGNOSTIC TROUBLE CODE (DTC) P0251 (SYMPTOM CODE D) 

(FLASH CODE 53) INJECTION PUMP MALFUNCTION

DIAGNOSTIC TROUBLE CODE (DTC) P0251 (SYMPTOM CODE E) 

(FLASH CODE 53) INJECTION PUMP MALFUNCTION

45

16 15 14 13 12 11 10 9

8 7 6 5 4 3 2 1

Battery
Voltage

Battery
Voltage

0.5
RED/
YEL

2.0
BLU/
RED

7

TCM

A / T

ECM Fuse

PSG(Pump Control Unit)

Injection
Pump

2

1

5

8

0.5
WHT

2.0
BLU/
RED

0.5
BLU/
BLK

0.5
RED

0.5
ORG

100

3

58

99

105

91

0.5
PNK

6

2.0
BLK

µP

CAN
Controller

Batt

Batt

IC

µP

0.5
BLU

Meter
10A

1.25
BLK

µP

Engine
Control
Module
(ECM)

ECM
Main Relay

6E–138

4JH1 ENGINE DRIVEABILITY AND EMISSIONS

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 
690rpm. 

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

4JH1 ENGINE DRIVEABILITY AND EMISSIONS

6E–139

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