Isuzu N-Series. Manual - part 709

6E-258    Engine Control System (4HK1) 

P1630 (Flash Code 36)

Circuit Description
This diagnostic applies to internal microprocessor
integrity conditions within the engine control module
(ECM).

Condition for Setting the DTC

• The ECM detects a malfunction in its internal

analog / digital (A/D) converter.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM limits accelerator control range.
• The ECM inhibits pilot injection.

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.

• A history DTC clears after 20 consecutive driving

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

DTC P1630 (Flash Code 36)

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.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Step 4

3

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 4

—

4

1.

Clear the DTCs with the Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 5

5

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

 Engine Control System (4HK1)    6E-259

P1631 (Flash Code 55)

Circuit Description
The engine control module (ECM) provides 5 volts
reference voltage through the reference circuit 1 to the
following sensors:

• Accelerator pedal position (APP) sensor 1
• PTO throttle sensor
• Idle up sensor

The 5 volts reference circuits are bussed together
outside the ECM. Therefore, a short circuit condition on
one sensor 5 volts reference circuit may affect the
entire 5 volt reference circuit 1. The ECM monitors the
voltage on the 5 volts reference circuit 1. If the ECM
detects the voltage is excessively low or high, this DTC
will set.

Condition for Running the DTC

• DTC P1630 is not set.
• The ignition switch is ON.
• The battery voltage is between 16 – 32 volts.

Condition for Setting the DTC
Either of following condition is met:

• The ECM detects that the 5 volts reference circuit

1 voltage is less than 4.5 volts.

• The ECM detects that the 5 volts reference circuit

1 voltage is more than 5.5 volts.

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.

DTC P1631 (Flash Code 55)
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.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic 

Aids

3

1.

Turn OFF the ignition.

2.

Disconnect the idle up sensor harness
connector.

3.

Connect a DMM between the 5 volts reference
circuit of the idle up sensor harness (pin 3 of
B-281 connector) and a known good ground.

4.

Turn ON the ignition, with engine OFF.

Is the DMM voltage less than the specified value?

5.5 volts

Go to Step 4

Go to Step 7

4

Is the DMM voltage more than the specified value
at Step 3?

4.5 volts

Go to Step 9

Go to Step 5

6E-260    Engine Control System (4HK1) 

5

1.

Keep the DMM with connected to the idle up
sensor harness connector.

2.

Turn OFF the ignition.

3.

Disconnect the accelerator pedal position
(APP) sensor harness connector.

4.

Turn ON the ignition, with the engine OFF.

Does the DMM voltage change to more than the
specified value when the APP harness connector is
disconnected?

4.5 volts

Go to Step 10

Go to Step 6

6

Notice:
If no PTO throttle sensor is installed, skip to Step 8.

1.

Keep the DMM with connected to the idle up
sensor harness connector.

2.

Turn OFF the ignition.

3.

Disconnect the PTO throttle sensor harness
connector.

4.

Turn ON the ignition, with the engine OFF.

Does the DMM voltage change to more than the
specified value when the PTO throttle sensor
harness connector is disconnected?

4.5 volts

Go to Step 11

Go to Step 8

7

1.

Test the 5 volts reference circuit 1 between the
engine control module (ECM) (pin 42 of J-191
connector) and the following components for a
short to battery or ignition voltage:

• APP sensor 1 (pin 4 of B-280 connector)
• PTO throttle sensor (pin 1 of J-166

connector)

• Idle up sensor (pin 3 of B-281 connector)

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

8

1.

Test the 5 volts reference circuit 1 between the
ECM (pin 42 of J-191 connector) and the
following components for a short to ground or
short to the low reference circuit:

• APP sensor 1 (pin 4 of B-280 connector)
• PTO throttle sensor (pin 1 of J-166

connector)

• Idle up sensor (pin 3 of B-281 connector)

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

9

Replace the idle up sensor. Refer to Idle Up Sensor
Replacement in this section.

Did you complete the replacement?

—

Go to Step 13

—

10

Replace the APP sensor. Refer to Accelerator
Pedal Position (APP) Sensor Replacement in this
section. (APP sensor 1 is internal to APP sensor
assembly)

Did you complete the replacement?

—

Go to Step 13

—

11

Replace the PTO throttle sensor.

Did you complete the replacement?

—

Go to Step 13

—

Step

Action

Value(s)

Yes

No

 Engine Control System (4HK1)    6E-261

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 3

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