Isuzu N-Series. Service manual - part 690

6E-182    Engine Control System (4HK1) 

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 13

—

13

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Start the engine.

5.

Operate the vehicle within the Conditions for
Running the DTC.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 14

14

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

No

 Engine Control System (4HK1)    6E-183

P0488 (Flash Code 45)

Circuit Description
The engine control module (ECM) controls the EGR
valve opening based on the barometric pressure,
engine speed, engine coolant temperature and fuel
injection quantity. The ECM controls the EGR valve by
controlling the EGR motor. The EGR valve position is
detected by the EGR valve position sensor, and
relayed to ECM. If the ECM detects a variance between
the actual EGR position and desired EGR position for a
calibrated amount of time while the EGR valve is
commanded open, this DTC will set.

Condition for Running the DTC

• DTCs P0485, P0486, P1630 and P1635 are not

set.

• The ignition switch is ON.
• The battery voltage is between 20 – 32 volts.
• The ignition voltage is more than 18 volts.
• The desired EGR valve position is stable.

Condition for Setting the DTC

• The ECM detects a variance between the actual

EGR valve position and desired valve position is
more than 20% for longer than 20 seconds when
the EGR solenoid command duty is more than
90%.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM inhibits EGR valve control.

Condition for Clearing the MIL / DTC

• The ECM turns OFF the MIL when the key is

cycled after a current DTC clears.

• A current DTC clears when the diagnostic runs and

does not fail at next driving cycle.

• A history DTC clears after 20 consecutive driving

cycles without a fault. Or clear with the Tech 2 or
accelerator pedal operation.

Diagnostic Aid

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

• A sticking or intermittently sticking EGR valve may

set this DTC.

DTC P0488 (Flash Code 45)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic 

System Check – 

Engine Controls

2

1.

Install the Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Is DTC P0485 or P0486 set?

—

Go to Applicable 

DTC

Go to Step 3

3

1.

Clear the DTCs with the Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Perform the EGR Control test with the Tech 2
several times.

5.

Command the Desired EGR Position
“Increase” and “Decrease” with the Tech 2
while observing the EGR Position Variance.

Does the EGR Position Variance parameter follow
within the specified value?

± 5%

Go to Diagnostic 

Aids

Go to Step 4

6E-184    Engine Control System (4HK1) 

4

1.

Turn OFF the ignition for 30 seconds.

2.

Disconnect the EGR valve harness connector.

3.

Connect a test lamp between the EGR valve
motor voltage feed circuit (pin 4 of E-94
connector) and a known good ground.

4.

Turn ON the ignition, with the engine OFF.

Does the test lamp blink then go out?

—

Go to Step 6

Go to Step 5

5

Does the test lamp continuously illuminate at Step
4?

—

Go to Step 10

Go to Step 9

6

1.

Turn OFF the ignition for 30 seconds.

2.

Connect a test lamp between the EGR valve
duty signal circuit (pin 6 of E-94 connector)
and a known good ground.

3.

Turn ON the ignition, with the engine OFF.

Does the test lamp blink then go out (note that the
test lamp will not blink normally)?

—

Go to Step 14

Go to Step 7

7

Does the test lamp continuously illuminate at Step
6?

—

Go to Step 11

Go to Step 8

8

1.

Turn OFF the ignition.

2.

Connect a test lamp between the EGR valve
duty signal circuit (pin 6 of E-94 connector)
and battery voltage.

3.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 12

Go to Step 13

9

1.

Test the EGR valve motor voltage feed circuit
between the engine control module (ECM)
(pin 111 of E-111 connector) and the EGR
valve (pin 4 of E-94 connector) for the
following conditions:

• An open circuit
• A short to ground
• A short to the EGR valve position sensor

low reference circuit

• High resistance

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 16

10

1.

Test the EGR valve motor voltage feed circuit
between the ECM (pin 111 of E-111 connector)
and the EGR valve (pin 4 of E-94 connector)
for a short to battery or ignition voltage.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 19

11

1.

Test the EGR valve motor duty signal circuit
between the ECM (pin 103 of E-111
connector) and the EGR valve (pin 6 of E-94
connector) for a short to battery or ignition
voltage.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 19

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-185

12

1.

Test the EGR valve motor duty signal circuit
between the ECM (pin 103 of E-111
connector) and the EGR valve (pin 6 of E-94
connector) for the following conditions:

• A short to ground
• A short to the EGR valve position sensor

low reference circuit

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 19

13

1.

Test the EGR valve motor duty signal circuit
between the ECM (pin 103 of E-111
connector) and the EGR valve (pin 6 of E-94
connector) for an open circuit or high
resistance.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 15

14

1.

Test the EGR valve motor voltage feed circuit
and motor duty signal circuit between the
ECM (pins 103 and 111 of E-111 connector)
and the EGR valve (pins 4 and 6 of E-94
connector) for a short circuit each other.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 19

15

1.

Turn OFF the ignition.

2.

Disconnect the EGR valve harness connector.

3.

Inspect for an intermittent and for poor
connections at the EGR valve harness
connector (pins 4 and 6 of E-94 connector).

4.

Disconnect the ECM harness connector.

5.

Inspect for an intermittent and for a poor
connection on the EGR valve motor duty
signal circuit at the harness connector of the
ECM (pin 103 of E-111 connector).

6.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 17

16

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent and for a poor
connection on the EGR valve motor voltage
feed circuit at the harness connector of the
ECM (pin 111 of E-111 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 20

Go to Step 19

17

Replace the EGR valve. Refer to EGR Valve
Replacement in this section.

Did you complete the replacement?

—

Go to Step 18

—

Step

Action

Value(s)

Yes

No