Jeep XJ. Manual - part 841

Symptom List:

P0442-EVAP LEAK MONITOR MEDIUM (0.040) LEAK DETECTED
P0455-EVAP LEAK MONITOR LARGE LEAK DETECTED
P0456-EVAP LEAK MONITOR SMALL LEAK DETECTED (.020)

Test Note:

All symptoms listed above are diagnosed using the same tests.

The title for the tests will be P0442-EVAP LEAK MONITOR
MEDIUM (0.040) LEAK DETECTED.

When Monitored and Set Condition:

P0442-EVAP LEAK MONITOR MEDIUM (0.040) LEAK DETECTED

When Monitored:

Immediately after a cold start, with battery/ambient temperature

between 40 deg. F and 90 deg. F and coolant temperature within 10 deg. F of battery/
ambient.

Set Condition:

If there is a leak larger than 0.040

9 and smaller than 0.0809 in the

evaporative system.

P0455-EVAP LEAK MONITOR LARGE LEAK DETECTED

When Monitored:

Immediately after a cold start, with battery/ambient temperature

between 40 deg. F and 90 deg. F and coolant temperature within 10 deg. F of battery/
ambient.

Set Condition:

There is a leak larger than 0.080

9 in the evaporative system.

P0456-EVAP LEAK MONITOR SMALL LEAK DETECTED (.020)

When Monitored:

Immediately after a cold start, with battery/ambient temperature

between 40 deg. F and 90 deg. F and coolant temperature within 10 deg. F of battery/
ambient.

Set Condition:

There is a leak larger than 0.080

9 in the evaporative system.

POSSIBLE CAUSES

CONFIRMED LEAK IN THE EVAP SYSTEM

INTERMITTENT LDP MONITOR FAILURE

TEST

ACTION

APPLICABILITY

Note: A loose gas cap could have caused this DTC to set. Make sure gas cap
is tight and in good condition. Ensure the gas cap meets OEM specifications.
Turn the ignition on.
With the DRBIII

t, read DTC’s.

Is the DTC Specific Good Trip Counter displayed and equal to zero?

All

Yes

→

Go To

→

Go To

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DRIVEABILITY - GAS

TEST

ACTION

APPLICABILITY

To continue testing you will need Miller Tools #6872A (Evap System Pressure Pump)
and #8382 (Gas Cap Tester/Adapter).
Warning: The test equipment is designed to be used to pressurize the
vehicles Evaporative System only. Using the equipment in a manner for
which it was not designed could be harmful.
Warning: Keep lighted cigarettes, sparks, flames, and other ignition sources
away from the test area to prevent the ignition of explosive gases. Keep the
test area well ventilated.
Note: The fuel tank should have between 20% and 80% of fuel tank capacity
to properly test the Evap system.
Attach the power source clip (red) of Miller Tool #6872A to Battery (+) and the ground
clip (black) to Battery (-).
Perform the Evaporative System Pressure Pump self test that is specified on the
tester cover.
Remove gas cap and install Miller Tool #8382 on vehicle. Install gas cap to Miller Tool
#8382. Attach the pressure supply hose from Miller Tool #6872A to the fitting on
#8382.
Disconnect the vacuum supply hose at the Leak Detection Pump. Connect and apply
a continuous vacuum supply (i.e. 20

9Hg) to the Leak Detection Pump. A vacuum

pump such as an A/C recovery unit works well.
Ignition on, engine not running.
With the DRBIII

t in System Tests, select 9Leak Detect Pump Test.9 Read instructions

and then press Enter. Select: #3 - HOLD PSI.
On Miller Tool #6872A, set the Pressure/Hold switch to Open and set the Vent switch
to Closed. Turn the pump timer On and watch the gauge.
Note: If the pressure does not build up, there is obviously a large leak in the
system and the presence of strong fuel odor may be present. A visual
inspection should find a leak of substantial size.
When the gauge pressure reaches 14

9H2O, turn the Pressure/Hold Valve to Closed.

Turn the pump timer off. Note the time and pressure. After 10 sec of stabilization
time.
Did the pressure drop more than 6

9H2O in 2 minutes?

All

Yes

→

Go To

→

Go To

Note: A thorough visual inspection of the Evap system hoses, tubes, and
connections may save time in your diagnosis. Look for any physical damage
or signs of wetness at connections. The strong smell of fuel vapors may aid
diagnosis also.
To continue testing, you will need Miller Tool #6904A (Ultrasonic Leak Detector.)
NOTE: The LDP System Test should still be running. If the DRBIII

t read has

timed out, restart the System Test.
Using Miller Tool #6872A, set the Pressure/Hold Switch to Open, and the Vent Switch
to Closed. Turn the pump timer on to pressurize/re-pressurize the Evap System.
Using the Ultrasonic Leak Detector, start listening for leaks in the Evap System.
Carefully leak test all hoses, tubes, and connections.
Were any leaks heard with the Ultrasonic Leak Detector?

All

Continue

Repair or replace the leaking component as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 6.

126

DRIVEABILITY - GAS

P0442-EVAP LEAK MONITOR MEDIUM (0.040) LEAK DETECTED —

Continued

TEST

ACTION

APPLICABILITY

At this time, the conditions required to set the DTC are not present.
Note: Use the Freeze Frame Data to help you duplicate the conditions that
set the DTC. Pay particular attention to the DTC set conditions, such as,
VSS, MAP, ECT, and Load.
Note: A thorough visual inspection of the Evap system hoses, tubes, and
connections may save time in your diagnosis. Look for any physical damage
or signs of wetness at connections. The strong smell of fuel vapors may aid
diagnosis also.
Note: Refer to any Technical Service Bulletins (TSB’s) that may apply.
With the DRBIII

t in System Tests, perform the LDP Monitor Test. This will force the

PCM to run the LDP Monitor. If the monitor fails, further diagnosis is required to
find faulty component. If the monitor passes, the condition is not present at this time.
Were any problems found?

All

Yes

→

Repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 6.

→

Test Complete.

127

DRIVEABILITY - GAS

P0442-EVAP LEAK MONITOR MEDIUM (0.040) LEAK DETECTED —

Continued

Symptom:

P0443-EVAP PURGE SOLENOID CIRCUIT

When Monitored and Set Condition:

P0443-EVAP PURGE SOLENOID CIRCUIT

When Monitored:

At ignition key on and battery voltage greater than 10.4 volts, during

initialization or power-up.

Set Condition:

Not powering down, not in limp-in and time since last solenoid activation

is greater than 72 micro seconds. The PCM will set a trouble code if the actual state of the
solenoid does not match the intended state on two consecutive key cycles.

POSSIBLE CAUSES

FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN

EVAP PURGE SOLENOID CONTROL CIRCUIT OPEN

EVAP PURGE SOLENOID CONTROL CIRCUIT SHORTED TO GROUND

WIRING HARNESS INTERMITTENT

EVAP PURGE SOLENOID

POWERTRAIN CONTROL MODULE

TEST

ACTION

APPLICABILITY

Turn the ignition on.
With the DRBIII

t, read DTC’s.

Is the DTC Specific Good Trip Counter displayed and equal to zero for P0443?

All

Yes

→

Go To

→

Go To

Turn the ignition off.
Disconnect the Evap Purge Solenoid connector.
Measure the resistance between the terminals of the Evap Purge Solenoid.
Is the resistance between 30.0 and 40.0 ohms?

All

Yes

→

Go To

→

Replace the Evap Purge Solenoid.
Perform POWERTRAIN VERIFICATION TEST VER - 5.

Turn the ignition off.
Disconnect the Evap Purge Solenoid harness connector.
Note: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Measure the Fused Ignition Switch Output Circuit at the Evap Purge Solenoid
harness connector.
Is the voltage above 10.0 volts?

All

Yes

→

Go To

→

Repair the open Fused Ignition Switch Output Circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 5.

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