Isuzu N-Series. Manual - part 710

6E-262    Engine Control System (4HK1) 

P1632 (Flash Code 55)

Circuit Description
The engine control module (ECM) provides 5 volts
reference voltage through the reference circuit 2 to the
following sensors:

• Accelerator pedal position (APP) sensor 2
• Barometric pressure (BARO) sensor

The ECM also provides 5 volts reference voltage
through the reference circuit 5 to the following sensors:

• Fuel rail pressure (FRP) sensor
• EGR valve position sensor

The 5 volts reference circuits 2 and 5 are independent
of each other outside of the ECM, but are bussed
together inside the ECM. Therefore, a short circuit
condition on one sensor 5 volts reference circuit may
affect the entire 5 volt reference circuit 2 and 5. The
ECM monitors the voltage on the 5 volts reference
circuit 2 and 5. If the ECM detects the voltage is
excessively low or high, this DTC and DTC P1635 will
also 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

2 or 5 voltage is less than 4.5 volts.

• The ECM detects that the 5 volts reference circuit

2 or 5 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 limits accelerator control range.
• The ECM inhibits pilot injection.
• The ECM inhibits EGR valve control.
• The ECM inhibits exhaust brake control.

Condition for Clearing the MIL / DTC

• The ECM turns OFF the MIL and exhaust brake

indicator lamp 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.

Diagnostic Aid

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

DTC P1632 (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 EGR valve harness connector.

3.

Connect a DMM between the 5 volts reference
circuit of the EGR valve position sensor
harness (pin 1 of E-94 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 8

4

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

4.5 volts

Go to Step 10

Go to Step 5

 Engine Control System (4HK1)    6E-263

5

1.

Keep the DMM with connected to the EGR
valve position sensor harness connector.

2.

Turn OFF the ignition.

3.

Disconnect the fuel rail pressure (FRP) 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 FRP sensor harness
connector is disconnected?

4.5 volts

Go to Step 11

Go to Step 6

6

1.

Keep the DMM with connected to the EGR
valve position sensor harness connector.

2.

Turn OFF the ignition.

3.

Disconnect the barometric pressure (BARO)
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 BARO sensor harness
connector is disconnected?

4.5 volts

Go to Step 13

Go to Step 7

7

1.

Keep the DMM with connected to the EGR
valve position 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 sensor harness
connector is disconnected?

4.5 volts

Go to Step 12

Go to Step 9

8

1.

Test the 5 volts reference circuit 2 between the
engine control module (ECM) (pin 61 of J-191
connector) and the following components for a
short to battery or ignition voltage:

• APP sensor 2 (pin 1 of B-280 connector)
• BARO sensor (pin 3 of B-422 connector)

2.

Test the 5 volts reference circuit 5 between the
ECM (pin 87 of E-111 connector) and the
following components for a short to battery or
ignition voltage:

• FRP sensor (pin 3 of E-113 connector)
• EGR position sensor (pin 1 of E-94

connector)

3.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 14

Step

Action

Value(s)

Yes

No

6E-264    Engine Control System (4HK1) 

9

1.

Test the 5 volts reference circuit 2 between the
ECM (pin 61 of J-191 connector) and the
following components for a short to ground or
short to the low reference circuit:

• APP sensor 2 (pin 1 of B-280 connector)
• BARO sensor (pin 3 of B-422 connector)

2.

Test the 5 volts reference circuit 5 between the
ECM (pin 87 of E-111 connector) and the
following components for a short to ground or
short to the low reference circuit:

• FRP sensor (pin 3 of E-113 connector)
• EGR position sensor (pin 1 of E-94

connector)

3.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 14

10

Replace the EGR valve. Refer to EGR Valve
Replacement in this section. (EGR valve position
sensor is internal to EGR valve)

Did you complete the replacement?

—

Go to Step 15

—

11

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

Did you complete the replacement?

—

Go to Step 15

—

12

Replace the APP sensor. Refer to Accelerator
Pedal Position (APP) Sensor Replacement in this
section. (APP sensor 2 is internal to APP sensor
assembly)

Did you complete the replacement?

—

Go to Step 15

—

13

Replace the BARO sensor. Refer to Barometric
Pressure (BARO) Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 15

—

14

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 15

—

15

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 16

16

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-265

P1633 (Flash Code 55)

Circuit Description
The engine control module (ECM) has ability to provide
5 volts reference voltage through the reference circuit
3. But it is not used. The ECM provides 5 volts
reference voltage through the reference circuit 4 to the
boost pressure sensor. The 5 volts reference circuits 3
and 4 are independent of each other outside of the
ECM, but are bussed together inside the ECM.
Therefore, a short circuit condition on one sensor 5
volts reference circuit may affect the entire 5 volt
reference circuit 3 and 4. The ECM monitors the
voltage on the 5 volts reference circuit 3 and 4. If the
ECM detects the voltage is excessively low or high, this
DTC and DTC P1634 will also 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

3 or 4 voltage is less than 4.5 volts.

• The ECM detects that the 5 volts reference circuit

3 or 4 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 limits accelerator control range.
• The ECM inhibits pilot injection.
• 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.

• 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 P1633 (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 DTC P1634

Go to Diagnostic 

Aids