Content .. 689 690 691 692 ..

Isuzu N-Series. Manual - part 691

6E-186 Engine Control System (4HK1)

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

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

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 Step 20

Go to Step 19

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 20

—

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Operate the vehicle within the Conditions for
Running the DTC.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 21

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

Engine Control System (4HK1) 6E-187

P0500 (Flash Code 25)

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 ignition voltage is more than 18 volts.
• The engine speed is more than 2000 RPM.
• The commanded fuel is OFF (accelerator pedal is

released).

Condition for Setting the DTC

• The ECM detects that the VSS signals are not

generated for 5 seconds.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

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.

• Electrical or magnetic interference may affect

intermittent condition.

DTC P0500 (Flash Code 25)
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

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check –

Engine Controls

Install the Tech 2.

Drive the vehicle.

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

Turn OFF the ignition.

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

Is the Meter (10A) fuse open?

—

Go to Step 4

Go to Step 5

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

Did you complete the repair?

—

Go to Step 16

—

6E-188 Engine Control System (4HK1)

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

Visually inspect the VSS for the following
conditions:

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

damage

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 6

Turn OFF the ignition.

Disconnect the VSS harness connector.

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.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 7

Go to Step 9

Keep the ignition switch ON.

Connect a test lamp between the low
reference circuit of the VSS harness (pin 2 of
J-32 connector) and battery voltage.

Does the test lamp illuminate?

—

Go to Step 8

Go to Step 10

Turn ON the ignition, with the engine OFF.

Intermittently jump the signal circuit of the
VSS (pin 3 of J-32 connector) with a test lamp
that is connected to 12 volts (apply from a
battery) 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 12 volts?

—

Go to Step 12

Go to Step 11

Repair the open circuit or high resistance on the
VSS ignition voltage feed circuit between the VSS
(pin 1 of J-32 connector) and the Meter (10A) fuse.

Did you complete the repair?

—

Go to Step 16

—

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-1).

Did you complete the repair?

—

Go to Step 16

—

Step

Action

Value(s)

Yes

Engine Control System (4HK1) 6E-189

Test the VSS signal circuit between the engine
control module (ECM) (pin 19 of J-191
connector) and the VSS (pin 3 of J-32
connector), then between the instrument
panel cluster (IPC) (pin 17 of B-52 connector)
and the VSS (pin 3 of J-32 connector) for the
following conditions:

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

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 13

Turn OFF the ignition.

Disconnect the VSS harness connector.

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

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 14

Turn OFF the ignition.

Disconnect the ECM harness connector.

Inspect for an intermittent and for a poor
connection on the VSS signal circuit at the
harness connector of the ECM (pin 19 of J-
191 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 16

Go to Step 15

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

Did you complete the replacement?

—

Go to Step 16

—

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 16

—

Reconnect all previously disconnected fuse or
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Drive the vehicle.

Observe the Vehicle Speed parameter with
the Tech 2.

Does the Vehicle Speed parameter indicate correct
vehicle speed?

—

Go to Step 17

Go to Step 3

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

Content .. 689 690 691 692 ..