Isuzu N-Series. Manual - part 712

6E-270    Engine Control System (4HK1) 

5

1.

Turn OFF the ignition.

2.

Connect a test lamp between the control
circuit of the exhaust brake solenoid valve
harness (pin 2 of J-31 connector) and battery
voltage.

3.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 9

Go to Step 6

6

1.

Keep the test lamp with connected.

2.

Perform the Exhaust Brake Control test with
the Tech 2.

3.

Command the Exhaust Brake ON with the
Tech 2.

Does the test lamp illuminate?

—

Go to Step 10

Go to Step 8

7

Repair the open circuit or high resistance on the
voltage feed circuit between the ECM (10A) fuse
and the exhaust brake solenoid valve (pin 1 of J-31
connector). Check the ECM (10A) fuse first.

Did you complete the repair?

—

Go to Step 14

—

8

1.

Test the control circuit between the engine
control module (ECM) (pin 15 of J-191
connector) and the exhaust brake solenoid
valve (pin 2 of J-31 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 14

Go to Step 11

9

1.

Test the control circuit between the ECM (pin
15 of J-191 connector) and the exhaust brake
solenoid valve (pin 2 of J-31 connector) for a
short to ground.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 13

10

1.

Turn OFF the ignition.

2.

Disconnect the exhaust brake solenoid valve
harness connector.

3.

Inspect for an intermittent and for poor
connections at the harness connector of the
exhaust brake solenoid valve (pins 1 and 2 of
J-31 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 12

11

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent and for a poor
connection on the exhaust brake solenoid
valve control circuit at the harness connector
of the ECM (pin 15 of J-191 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 13

12

Replace the exhaust brake solenoid valve. Refer to
Exhaust Brake Solenoid Valve Replacement in
Exhaust System section.

Did you complete the replacement?

—

Go to Step 14

—

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-271

13

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 14

—

14

1.

Reconnect all previously disconnected fuse or
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 15

15

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

6E-272    Engine Control System (4HK1) 

P1682 (Flash Code 46)

Circuit Description
The engine control module (ECM) controls the exhaust
brake which energizes the intake throttle solenoid valve
and exhaust brake solenoid valve based on vehicle
running condition. The ECM commands each solenoid
valve to close each throttle valve by applying vacuum.
If the ECM detects that a short to battery or ignition
voltage on the exhaust brake solenoid valve control
circuit, this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.
• The battery voltage is between 16 – 32 volts.
• The engine is running.

Condition for Setting the DTC

• The ECM detects a high voltage condition on the

exhaust brake solenoid valve control circuit for
longer than 10 seconds when the solenoid valve is
commanded ON.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM blinks the exhaust brake indicator lamp

when the diagnostic runs and fails.

• The ECM inhibits exhaust brake control.

Condition for Clearing the MIL / DTC

• The ECM turns OFF the MIL when the key is

cycled after a current DTC clears.

• The ECM turns OFF the exhaust brake indicator

lamp when the diagnostic runs and does not fail.

• A current DTC clears when the diagnostic runs and

does not fail.

• 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.

Test Description
The number below refers to the step number on the
diagnostic table.
3. If the exhaust brake solenoid valve control circuit
between the ECM and the solenoid valve is normal,
voltage level low DTC P1681 will set.

DTC P1682 (Flash Code 46)
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.

Turn ON the ignition, with the engine OFF.

4.

Perform the Exhaust Brake Control test with
the Tech 2.

5.

Command the Exhaust Brake ON with the
Tech 2.

Does the exhaust brake solenoid valve click when
commanded ON with the Tech 2 (note that intake
throttle solenoid valve also click when commanded
ON)?

—

Go to Diagnostic 

Aids

Go to Step 3

3

1.

Turn OFF the ignition.

2.

Disconnect the exhaust brake solenoid valve
harness connector.

3.

Start the engine.

4.

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

Does DTC P1681 set, but not DTC P1682?

—

Go to Step 5

Go to Step 4

 Engine Control System (4HK1)    6E-273

4

1.

Test the control circuit between the engine
control module (ECM) (pin 15 of J-191
connector) and the exhaust brake solenoid
valve (pin 2 of J-31 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 7

Go to Step 6

5

Replace the exhaust brake solenoid valve. Refer to
Exhaust Brake Solenoid Valve Replacement in
Exhaust System section.

Did you complete the replacement?

—

Go to Step 7

—

6

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 7

—

7

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.

Lift the driving wheels or drive the vehicle.

5.

Let the vehicle run so that the exhaust brake
may operate enough time (longer than 3
seconds).

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 8

8

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