Content .. 658 659 660 661 ..

Isuzu N-Series. Manual - part 660

6E-62 Engine Control System (4HK1)

Observe the FRP Regulator Feedback parameter
on the Tech 2 while cranking over the engine for 5
seconds.

Does the SCV Feedback parameter more than the
specified value during crank?

800 mA

Go to Fuel System

Check in the Fuel

System Section

Go to Step 8

Turn OFF the ignition.

Disconnect the FRP sensor harness
connector.

Inspect for an intermittent, for poor
connections and corrosion at the harness
connector of the FRP sensor (pins 1, 2 and 3
of E-113 connector).

Disconnect the ECM harness connector.

Inspect for an intermittent, for poor
connections and corrosion on each FRP
sensor circuit at the harness connector of the
ECM (pins 82, 87, 90 and 101 of E-111
connector).

Test for high resistance on each FRP sensor
circuit.

Repair the connection(s) or circuit(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 12

Go to Step 7

Replace the FRP sensor. Refer to Fuel Rail
Pressure (FRP) Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 12

—

Test the FRP regulator low control circuits
between the engine control module (ECM)
(pins 89 and 97 of E-111 connector) and the
FRP regulator (pin 2 of E-116 connector) for a
short to ground.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 12

Go to Step 11

Check for normal readings at key up for the
following sensor inputs: Use the Tech 2 Data
List or a known good vehicle to determine
nominal values.

• Coolant Temperature
• Barometric Pressure (BARO)
• Boost Pressure Sensor
• EGR Valve Position Sensor

Repair the circuit(s) or replace the sensor as
necessary.

Did you find and correct the condition?

—

Go to Step 12

Go to Step 10

Step

Action

Value(s)

Yes

Engine Control System (4HK1) 6E-63

Other possible causes for the no-start
condition:

• Engine mechanical timing
• Flywheel installed incorrectly causing the

crankshaft position (CKP) sensor to be
incorrectly timed to the engine.
Disconnect sensor and attempt to start
engine to verify.

• Heavily restricted intake or exhaust

plugged solid.

• Poor engine compression.
• Water or gasoline contamination in fuel.

Repair as necessary.

Did you find and correct the condition?

—

Go to Step 12

—

Important:
Replacement ECM must be programmed.

Replace the ECM. Refer to Engine Control Module
(ECM) Replacement / Fuel Injector ID Code Data
Programming in this section.

Did you complete the replacement?

—

Go to Step 12

—

Reconnect all previously disconnected
harness connector(s).

Turn OFF the ignition for 30 seconds.

Attempt to start the engine.

Does the engine start and continue to run?

—

Go to Step 13

Go to Step 2

Observe the DTC information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic

Trouble Code (DTC)

List

System OK

Step

Action

Value(s)

Yes

6E-64 Engine Control System (4HK1)

Engine Starts and Stalls

Description
The engine control module (ECM) constantly monitors
the information from various sensors. The ECM
controls the systems that affect engine performance.
The ECM performs the diagnostic function of the
system. The ECM can recognize operational
conditions, alert the driver through the malfunction
indicator lamp (MIL), and store diagnostic trouble
codes (DTCs). DTCs identify the faulty areas to aid the
technician in making repairs.
The main relay supplies power to external output
devices.

Diagnostic Aid

• Poor connection at the main relay

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, shorts to
ground, shorts to battery, and open circuits. If the
harness appears to be OK, observe the power
supply or data list display on the Tech 2 while
moving connectors and wiring harnesses related to
the main relay. A change in the scan tool display
will indicate the location of the fault.

• Air / water or gasoline contamination in the fuel

system.

Engine Starts and Stalls

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check –

Engine Controls

Does the engine fail to start?

—

Go to Engine

Cranks but Does

Not Run

Go to Step 3

Perform the following checks before
proceeding with this chart.

• Make sure the idle up control knob to the

lowest position. (Full counterclockwise
direction)

• Check for an adequate supply of fuel in

the fuel tank(s) and the quality of the fuel
(water or gasoline contamination). If the
outside temperature is very cold, the fuel
may be gelled.

• Check the battery cables for corrosion

and for tightness.

• Make an under cab visual inspection for

obvious fuel leaks and for fuel system
line problems.

• Make a vehicle inspection for obvious

intake or exhaust restrictions (collapsed
induction tubing or crushed exhaust).

• Check the engine control module (ECM)

connectors and ring terminal grounds for
tightness.

• Check the engine oil level viscosity and

quality.

Repair as necessary.

Did you find and correct the condition?

—

Go to Step 6

Go to Step 4

Engine Control System (4HK1) 6E-65

Turn ON the ignition with the engine OFF.

Install the Tech 2 if not installed.

Observe the following parameters for skewed
sensor readings:

• Fuel Rail Pressure (FRP) Sensor with the

engine OFF. The FRP Sensor should
read 0.9 – 1.0 volt with the key ON and
engine OFF. After the engine has
stopped running for a minimum 2
minutes.

• Boost Pressure and Barometric Pressure

(BARO) with the engine OFF. The Boost
Pressure and BARO parameters should
be within 7.0 kPa (1.0 psi) each other.

• Coolant Temperature with the engine

OFF and a cold engine. The Coolant
Temperature, Intake Air Temperature and
Fuel Temperature parameters should be
within 5

°C (9°F) each other.

Refer to the Tech 2 Data List for nominal
values.

Refer to appropriate DTC or schematic if a
problem was found and repair as necessary.

Did you find and correct the condition?

—

Go to Step 6

Go to Step 5

Other possible causes of engine stall:

• Incorrect crankshaft to camshaft timing or

sensor tooth / gear surface damage /
incorrect machining

• Poor fuel quality (water or gasoline

contamination)

• Fuel supply pump problem. Perform the

Rail Pressure Control test with the Tech
2. The Differential Fuel Rail Pressure
parameter should be within

± 5 MPa (±

725 psi) when commanded pressure
range.

• Fuel injector(s) problem. Perform the

Injector Balancing test with the Tech 2.
Repair the wire or replace the
appropriate fuel injector that does not
change engine speed when commanded
OFF. Perform the Injector Forced Drive
test with the Tech 2. Repair the wire or
replace the appropriate fuel injector that
does not create a clicking noise (solenoid
operating noise).

• ECM main relay circuit malfunction
• ECM power / grounding problem

Repair as necessary.

Did you find and correct the condition?

—

Go to Step 6

Possible fuel

related. Refer to

Fuel System Check

in the Fuel System

Section

Turn OFF the ignition for 30 seconds.

Start the engine and accelerate up and down
the RPM band.

Does the engine continue to run?

—

System OK

Go to Step 2

Step

Action

Value(s)

Yes

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