Isuzu engine C22NE / 22LE / 20LE. Service 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
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