Isuzu engine C22NE / 22LE / 20LE. Manual - part 74

DRIVEABILITY AND EMISSIONS  6E1-125

EVAPORATIVE EMISSIONS (EVAP)

CANISTER PURGE CONTROL SOLENOID VALVE CHECK (IF APPLICABLE)

Circuit Description

Canister purge is controlled by a solenoid valve that

allows manifold vacuum to purge the canister. The

engine control module (ECM) supplies a ground to

energize the solenoid valve (purge ON). The EVAP

(purge solenoid control is turned ON time) is

determined by engine operating conditions including

load, throttle position, coolant temperature and

ambient temperature. The duty cycle is calculated by

the ECM and the purge solenoid is enabled when the

appropriate conditions have been met:
• The engine run time after start is more than 60

seconds.

• The engine coolant temperature is above 30°C

(86°F).

• The fuel control system is operating in the “Closed-

Loop” mode (If applicable).

Diagnostic Aids

• Make a visual check of vacuum hoses.
• Check the throttle body for possible cracked or

plugged vacuum block.

• Check the malfunction indicator lamp for a possible

mechanical problem.

Test Description

The number(s) below refer to the step number(s) on

the Diagnostic Chart.

1. Check to see if the solenoid is open or closed. The

solenoid is normally de-energized in this step, so it

should be closed.

2.  This step checks to determine if the solenoid was

open due to an electrical circuit problem or a

defective solenoid.

3. This should normally energize the solenoid,

opening the valve and allowing the vacuum to drop

(Purge ON).

6E1-126  DRIVEABILITY AND EMISSIONS

Evaporative Emissions (EVAP) Canister Purge Valve Solenoid Check

Step

Action

Value(s)

Yes

No

1

1. Ignition OFF.

2.  Ignition ON, engine OFF.

3.  At the intake manifold, disconnect the hose that goes

to the pump solenoid.

4.  Using a hand vacuum purge with an attached vacuum

gauge 5-8840-0279-0, apply vacuum (10” Hg or 34

kPa) to the solenoid.

Does the solenoid hold vacuum?

-

Go to Step 3

Go to Step 2

2

1.  Disconnect the solenoid electrical connector.

2.  As in Step 1, apply vacuum (10” Hg or 34 kPa) to the

solenoid.

Does the solenoid hold vacuum?

-

Go to Step 4

Go to Step 7

3

1.  At the intake manifold, put a cap over the vacuum port

where the hose was disconnected for testing.

This is to prevent a vacuum leak when the engine is

started.

2. Ignition OFF.

3.  Install the scan tool.

4.  Apply vacuum to the purge control solenoid with the

hand vacuum pump.

5.  Start the engine, run at 2500 RPM.

6.  Using the Scan Tool command the purge control

solenoid ON.

Did the vacuum drop when the purge was turned on?

-

Go to Step 8

Go to Step 9

4

Check for a short to ground or open in the wire between

the solenoid and the ECM.

Is there a problem?

-

Go to Step 5

Go to Step 6

5

Repair the faulty wire.

Is the action complete?

-

Verify repair

-

6

Replace the EPROM or ECM.

Note) Refer to 6E1-243.

-

Verify repair

-

7

Replace the faulty purge control solenoid. Refer to On-

Vehicle Service, EVAP Canister Purge Solenoid.

Is the action complete?

-

.

Verify repair

-

8

1.  Turn the ignition OFF.

2.  Verify the purge hose nipple is not plugged.

-

No problem

found in the

EVAP

emission

canister

purge valve

check.

Refer to

Diagnostic

Aids

9

1.  Turn the Ignition OFF.

2.  Disconnect the solenoid's electrical connector.

3.  Connect a test lamp between the harness terminals.

4.  Turn the ignition ON.

Does the test lamp light?

-

Go to Step 7

Go to Step 10

DRIVEABILITY AND EMISSIONS  6E1-127

Evaporative Emissions (EVAP) Canister Purge Valve Solenoid Check (Cont'd)

Step

Action

Value(s)

Yes

No

10

Probe each terminal of the solenoid valve electrical

connector with a test lamp to ground.

Does the test lamp light on both terminals?

-

Go to Step 11

Go to Step 12

11

Repair the short to voltage in the wire between the

solenoid and the ECM.

Is the action complete?

-

Verify repair

-

12

Does the ignition feed terminals light the test lamp?

-

Go to Step 13

Go to Step 14

13

Check for an open in the wire between the purge control

solenoid and the ECM.

Was there an open circuit?

-

Go to Step 15

Go to Step 6

14

Repair the open in the ignition feed wire.

Is the action complete?

-

Verify repair

-

15

Repair the open wire.

Is the action complete?

-

Verify repair

-

6E1-128  DRIVEABILITY AND EMISSIONS