Isuzu N-Series. Manual - part 770

 Engine Control System (4JH1)    6E-131

4

1.

Turn OFF the ignition.

2.

Disconnect the engine control module (ECM)
harness connector.

3.

Inspect for an intermittent and for a poor
connection on VSS circuit at the harness
connector of the ECM (pin 68 of B-234
connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Step 5

5

1.

Remove the VSS.  Refer to Vehicle Speed
Sensor (VSS) Replacement in this section.

2.

Visually inspect the VSS for the following
conditions:

• Physical damage
• Being loose
• Improper installation

3.

The following conditions may cause this DTC
to set:

• Electromagnetic interference in the VSS

circuits

4.

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Step 6

6

Replace the VSS.  Refer to Vehicle Speed Sensor
(VSS) Replacement 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.

Drive the vehicle.

5.

Observe the Vehicle Speed parameter with
the Tech 2.

Does the Vehicle Speed parameter indicate correct
vehicle speed?

—

Go to Step 8

Go to Step 2

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

6E-132    Engine Control System (4JH1) 

P0500 (Symptom Code B) (Flash Code 24)

Circuit Description
The vehicle speed sensor (VSS) is used by the engine
control module (ECM) and speedometer, which
generates a speed signal from the transmission output
shaft.  The VSS has the following circuits.

• Ignition voltage feed circuit
• VSS signal circuit
• VSS low reference circuit

The VSS uses a hall effect element.  It interacts with
the magnetic field created by the rotating magnet and
outputs square wave pulse signal.  The ECM calculates
the vehicle speed by the VSS.  If the ECM detects VSS
signals are not generated, this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.
• The engine speed is higher than 3600 RPM.
• The fuel injection quantity is more than 41 mg/strk.

Condition for Setting the DTC

• The ECM detects that the vehicle speed is lower

than 1.5 km/h (1 MPH) for 60 seconds.

Action Taken When the DTC Sets

• The ECM does not illuminate the malfunction

indicator lamp (MIL) when the diagnostic runs and
fails.

Condition for Clearing the DTC

• A history DTC clears after 40 consecutive driving

cycles without a fault.  Or clear with the Tech 2.

Diagnostic Aids

• Electrical or magnetic interference may affect

intermittent condition.

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

DTC P0500 (Symptom Code B) (Flash Code 24)
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.

Drive the vehicle.

3.

Observe the Vehicle Speed parameter with
the Tech 2.

Does the Vehicle Speed parameter indicate correct
vehicle speed?

—

Go to Diagnostic 

Aids

Go to Step 3

3

1.

Turn OFF the ignition.

2.

Inspect the Meter (10A) fuse (F-16) in the
glove box fuse block.

Is the Meter (10A) fuse (F-16) open?

—

Go to Step 4

Go to Step 5

4

Replace the Meter (10A) fuse (F-16).  If the fuse
continues to open, repair the short to ground on
one of the circuits that fed by the Meter (10A) fuse
(F-16) or replace the shorted attached component
fed by the Meter (10A) fuse (F-16).

Did you complete the repair?

—

Go to Step 18

—

 Engine Control System (4JH1)    6E-133

5

1.

Remove the vehicle speed sensor (VSS).
Refer to Vehicle Speed Sensor (VSS)
Replacement in this section.

2.

Visually inspect the VSS for the following
conditions:

• Physical damage
• Being loose
• Improper installation
• For transmission output shaft teeth

damage

3.

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 6

6

1.

Turn OFF the ignition.

2.

Disconnect the VSS harness connector.

3.

Connect a test lamp between the ignition
voltage feed circuit of the VSS harness (pin 1
of J-32 connector) and a known good ground.

4.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 7

Go to Step 9

7

1.

Keep the ignition switch ON.

2.

Connect a test lamp between the ignition
voltage feed circuit and low reference circuit of
the VSS harness (pins 1 and 2 of J-32
connector).

Does the test lamp illuminate?

—

Go to Step 8

Go to Step 10

8

1.

Turn ON the ignition, with the engine OFF.

2.

Intermittently jump the signal circuit of the
VSS (pin 3 of J-32 connector) with a test lamp
that is connected to a known good ground
while monitoring the Vehicle Speed parameter
with the Tech 2.

Does the Tech 2 indicate any vehicle speed when
the circuit is intermittently pulled to ground?

—

Go to Step 12

Go to Step 11

9

1.

Test the VSS ignition voltage feed circuit
between the VSS (pin 1 of J-32 connector)
and the instrument panel cluster (IPC) (pin 3
of B-55 connector) for an open circuit or high
resistance, then between the IPC (pin 8 of B-
51 connector) and the Meter (10A) fuse (F-16)
for an open circuit or high resistance.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 13

10

Repair the open or high resistance in the VSS low
reference circuit between the VSS (pin 2 of J-32
connector) and ground terminal (B-7 terminal).

Did you complete the repair?

—

Go to Step 18

—

Step

Action

Value(s)

Yes

No

6E-134    Engine Control System (4JH1) 

11

1.

Test the VSS signal circuit between the engine
control module (ECM) (pin 68 of B-234
connector) and the VSS (pin 3 of J-32
connector).

• An open circuit
• A short to ground
• A short to battery or ignition voltage
• High resistance

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 14

12

1.

Turn OFF the ignition.

2.

Disconnect the VSS harness connector.

3.

Inspect for an intermittent and for poor
connections at the harness connector of the
VSS (pins 1, 2 and 3 of J-32 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 15

13

1.

Turn OFF the ignition.

2.

Disconnect the IPC B-51 and B-55 harness
connector.

3.

Inspect for an intermittent and for poor
connections at the harness connector of the
IPC (pin 8 of B-51 and pin 3 of B-55
connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 16

14

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent and for a poor
connection on the VSS signal circuit at the
harness connector of the ECM (pin 68 of B-
234 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 17

15

Replace the VSS.  Refer to Vehicle Speed Sensor
(VSS) Replacement in this section.

Did you complete the replacement?

—

Go to Step 18

—

16

Replace the IPC (meter assembly).  Refer to Meter
Replacement in electrical section.

Did you complete the replacement?

—

Go to Step 18

—

17

Important:
Replacement ECM must be programmed.

Replace the ECM.  Refer to Engine Control Module
(ECM) Replacement in this section.

Did you complete the replacement?

—

Go to Step 18

—

Step

Action

Value(s)

Yes

No