Dodge ZB 2005 Service Manual page 1128

The pumping cycle is repeated as the solenoid is
turned on and off. When the evaporative system
begins to pressurize, the pressure on the bottom of
the diaphragm will begin to oppose the spring
pressure, slowing the pumping action. The PCM
watches the time from when the solenoid is de-
energized, until the diaphragm drops down far
enough for the reed switch to change from opened to
closed. If the reed switch changes too quickly, a leak
may be indicated. The longer it takes the reed
switch to change state, the tighter the evaporative
system is sealed. If the system pressurizes too
quickly, a restriction somwhere in the EVAP system
may be indicated.
PUMPING ACTION
During portions of this test, the PCM uses the
reed switch to monitor diaphragm movement. The
solenoid is only turned on by the PCM after the reed
switch changes from open to closed, indicating that
the diaphragm has moved down. At other times
during the test, the PCM will rapidly cycle the LDP
solenoid on and off to quickly pressurize the system.
During rapid cycling, the diaphragm will not move
enough to change the reed switch state. In the state
of rapid cycling, the PCM will use a fixed time
interval to cycle the solenoid.
If the system does not pass the EVAP Leak
Detection Test, the following DTCs may be set:
• P0442 – EVAP LEAK MONITOR 0.040 LEAK
DETECTED
• P0455 – EVAP LEAK MONITOR LARGE LEAK
DETECTED
• P0456 – EVAP LEAK MONITOR 0.020 LEAK
DETECTED
•
P1486 – EVAP LEAK MON PINCHED HOSE
FOUND
• P1494 – LEAK DETECTION PUMP SW OR
MECH FAULT
•
P1495 – LEAK DETECTION PUMP SOLENOID
CIRCUIT
ENABLING CONDITIONS TO RUN EVAP LEAK
DETECTION TEST
1. Cold start: with ambient temperature (obtained
from modeling the inlet air temperature sensor
on passenger vehicles and the battery tempera-
ture sensor on Jeep & truck vehicles) between
4°C (40°F) and 32°C (90°F) for 0.040 leak. Be-
tween 4°C (40°F) and 29°C (85°F) for 0.020 leak.
2. Engine coolant temperature within: -12° to -8°C
(10° to 18°F) of battery/ambient.
3. Battery voltage between 10 and 15 volts.
GENERAL INFORMATION
NOTE: If battery voltage drops below 10 volts
for more than 5 seconds during engine
cranking, the evap leak detection test will not
run.
4. Low fuel warning light off (fuel level must be
between 15% and 85%).
5. MAP sensor reading 22 in Hg or above (This is
the manifold absolute pressure, not vacuum).
6. No engine stall during test.
NOTE: The following values are approximate
and vehicle specific. Use the values seen in
pre test/monitor test screen on the DRBIII .
See TSB 25-02-98 for more detail.
A DTC will not set if a one-trip fault is set or if the
MIL is illuminated for any of the following:
• Purge Solenoid
•
All engine Controller Self Test Faults
•
All Cam and/or Crank Sensor Faults
• MAP Sensor Faults
• Ambient/Battery Temperature Sensor Electrical
Faults
•
All Coolant Sensor Faults
• All TPS Faults
• LDP Pressure Switch Faults
• EGR Solenoid Electrical Faults
•
All Injector Faults
• Baro Out Of Range
• Vehicle Speed Faults
• LDP Solenoid Circuit
FIGURE 6 SECTION 1
When the ignition key is turned to "ON", the LDP
diaphragm should be in the down position and the
LDP reed switch should be closed. If the EVAP
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