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Isuzu KB P190. Manual - part 591

6E–194

ENGINE DRIVEABILITY AND EMISSIONS

Using the DVM and check the purge solenoid valve
signal circuit.

1. Ignition “On”, engine “Off”.

2. Disconnect the purge solenoid valve connector.

3. Check the circuit for short to voltage circuit.

Was the DVM indicated voltage?

—

Repair faulty

harness and

verify repair

Go to Step 10

Substitute a known good purge solenoid valve and
recheck.
Was the problem solved?

—

Go to Step 11

Go to Step 12

Replace the purge solenoid valve.
Was the problem solved?

—

Verify repair

Go to Step 12

Is the ECM programmed with the latest software
release?
If not, download the latest software to the ECM using
the “SPS (Service Programming System)”.
Was the problem solved?

—

Verify repair

Go to Step 13

Replace the ECM.
Is the action complete?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobilizer system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobilizer System-ECM replacement” for
the ECM/Immobilizer linking procedure.

—

Verify repair

—

Step

Action

Value(s)

Yes

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ENGINE DRIVEABILITY AND EMISSIONS

6E–195

DIAGNOSTIC TROUBLE CODE (DTC) P0502 VEHICLE SPEED SENSOR (VSS)

CIRCUIT LOW INPUT

Condition for setting the DTC and action taken when the DTC sets

Circuit Description

The vehicle speed sensor has a magnet rotated by the
transmission output shaft. Attached to the sensor is a
hall effect circuit that interacts with the magnetic field
created by the rotating magnet. A 12-volt operating
supply for the speed sensor hall circuit is supplied from
the meter fuse.

Diagnostic Aids

• Poor connection at ECM: Inspect harness connectors

for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal to wire connection.

Code

Type

DTC Name

DTC Setting Condition

Fail-Safe (Back Up)

P0502

Vehicle Speed Sensor Circuit Low
Input

1. No DTC relating to MAP sensor, TPS, ECT

sensor, injector control circuit and ignition
control circuit.

2. Engine is running.
3. Vehicle speed is below 3km/h in power

condition or 2km/h in deceleration condi-
tion.

ECM uses 0km/h condition as substitute.

6E–196

ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0502 Vehicle Speed Sensor Circuit Low Input

Step

Action

Value(s)

Yes

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to Step 2

Go to On Board

Diagnostic

(OBD) System

Check

1. Connect the Tech 2.

2. Review and record the failure information.

3. Select “F0: Read DTC Infor By Priority” in “F0:

Diagnostic Trouble Code”.

Is the DTC P0502 stored as “Present Failure”?

—

Go to Step 3

Refer to

Diagnostic Aids

and Go to Step

1. Using the Tech2, ignition “On” and engine “Off”.

2. Select “Clear DTC Information” with the Tech2 and

clear the DTC information.

3. Operate the vehicle and monitor the “F5: Failed

This Ignition” in “F2: DTC Information”.

Was the DTC P0502 stored in this ignition cycle?

—

Go to Step 4

Refer to

Diagnostic Aids

and Go to Step

Check for poor/faulty connection at the VSS, meter,
immobilizer control unit (if equipped), ECM and other
connectors. If a poor/faulty connection is found, repair
the faulty terminal.
Was the problem found?

—

Verify repair

Go to Step 5

Remove the VSS from the housing case and visually
check.
Was the problem found?

—

Go to Step 19

Go to Step 6

9 10

C-56(J2)

B-68

B-24

E-44

ENGINE DRIVEABILITY AND EMISSIONS

6E–197

Using the DVM and check the VSS signal.

1. Ignition “On”, vehicle “Run (lift up)”.

2. Measure the VSS output voltage at sensor, meter,

immobilizer control unit (if equipped) and ECM.

Does the tester indicate specified value?

If a oscilloscope is available, monitor the VSS signal.
Does the oscilloscope indicate correct wave form?

Refer to

Diagnostic Aids

and Go to Step

Refer the table

Using the DVM and check the VSS power supply
circuit.

1. Ignition “On”, engine “Off”.

2. Disconnect the VSS connector.

3. Check the circuit for open or short to ground

circuit.

Was the DVM indicated specified value?

10 - 14.5V

Go to Step 9

Go to Step 8

Repair the open circuit between the VSS and meter
fuse.
Is the action complete?

—

Verify repair

—

Step

Action

Value(s)

Yes

Measurement Position

Voltage (V)

(AC Range)

If No

Good

VSS terminal 3 & GND

Approximately

7.0 V at 20km/h

Go to

Step 7

Meter B24 connector 9 &
GND

Go to

Step 11

Meter B24 connector 10 &
GND

Go to

Step 13

Immobilizer control unit B68
connector 6 & GND

Go to

Step 14

Immobilizer control unit B68
connector 8 & GND

Approximately

6.5V at 20km/h

Go to

Step 16

ECM C56 (J2) connector 23 &
GND

Go to

Step 17

  Vehicle Speed Sensor (VSS) Reference W ave Form

CH1
0V

CH2
0V



  Measurement Terminal: CH1: ECM J2-23(+) / CH2: VSS 3(+)
                                                        GND(-)
  Measurement Scale: CH1: 10V/div / CH2: 10V/div          50ms/div

Measurement Condition: Approximately 20km/h

Note: The vehicle is without immobilizer system,
CH1 signal is same as CH2.

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