Dodge ZB 2005, Service Manual

Page: 1130 / 1873

MIL will illuminate and a DTC will be stored based
on the size of leak detected. If no leak is detected
during the next test, the temporary fault will be
cleared.
DIAGNOSTIC TIPS
During diagnosis, you can compare the LDP so-
lenoid activity with the monitor sequence in Figure
6. If the PCM detects a problem that could set a
DTC, the testing is halted and LDP solenoid activ-
ity will stop. As each section of the test begins, it
indicates that the previous section passed success-
fully. By watching to see which tests complete, you
can see if any conditions are present that the PCM
considers abnormal.
For example, if the LDP solenoid is energized for
the test cycles to test for blockage (P1486), it means
that the LDP has already passed its test for P1494.
Then, if the PCM detects a possible blockage, it will
set a temporary fault without turning on the MIL
and continue the leak portion of the test. However,
the PCM will assume that the system is already
pressurized and skip the rapid pump cycles.
Always diagnose leaks, if possible, before discon-
necting connections. Disconnecting connections
may mask a leak condition.
Keep in mind that if the purge solenoid seat is
leaking, it could go undetected since the leak would
end up in the intake manifold. Disconnect the purge
solenoid at the manifold when leak checking. In
addition, a pinched hose fault (P1486) could set if
the purge solenoid does not purge the fuel system
properly (blocked seat). The purge solenoid must
vent the fuel system prior to the LDP system test. If
the purge solenoid cannot properly vent the system
the LDP cannot properly complete the test for
P1486 and this fault can set due to pressure being
in the EVAP system during the test sequence.
Multiple actuation’s of the DRBIII
t
Leak Detec-
tion Pump (LDP) Monitor Test can hide a 0.020 leak
because of excess vapor generation. Additionally,
any source for additional vapor generation can hide
a small leak in the EVAP system. Excess vapor
generation can delay the fall of the LDP diaphragm
thus hiding the small leak. An example of this
condition could be bringing a cold vehicle into a
warm shop for testing or high ambient tempera-
tures.
Fully plugged and partially plugged underhood
vacuum lines have been known to set MIL condi-
tions. P1494 and P0456 can be set for this reason.
Always, thoroughly, check plumbing for pinches or
blockage before condemning components.
TEST EQUIPMENT
The Evaporative Emission Leak Detector (EELD)
Miller Special Tool 8404 is capable of visually de-
tecting leaks in the evaporative system and will
take the place of the ultrasonic leak detector 6917A.
The EELD utilizes shop air and a smoke generator
to visually detect leaks down to 0.020 or smaller.
The food grade oil used to make the smoke includes
an UV trace dye that will leave telltale signs of the
leak under a black light. This is helpful when
components have to be removed to determine the
exact leak location. For detailed test instructions,
follow the operators manual packaged with the
EELD.
IMPORTANT
Be sure that the PCM has the latest software
update. Reprogram as indicated by any applicable
Technical Service Bulletin. After LDP repairs are
completed, verify the repair by running the
DRBIII
t
Leak Detection Pump (LDP) Monitor Test
as described in Technical Service Bulletin 18-12-99.
3.2.5 NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems, and conditions even though they could
have malfunctions that result in driveability prob-
lems. A diagnostic code may not be displayed for the
following conditions. However, problems with these
systems may cause a diagnostic code to be displayed
for other systems. For example, a fuel pressure
problem will not register a diagnostic code directly,
but could cause a rich or lean condition. This could
cause an oxygen sensor, fuel system, or misfire
monitor trouble code to be stored in the PCM.
Engine Timing − The PCM cannot detect an
incorrectly indexed timing chain, camshaft
sprocket, or crankshaft sprocket. The PCM also
cannot detect an incorrectly indexed distributor or
Cam Sensor.(*)
Fuel Pressure − Fuel pressure is controlled by
the fuel pressure regulator. The PCM cannot detect
a clogged fuel pump inlet filter, clogged in-line filter,
or a pinched fuel supply.(*)
Fuel Injectors − The PCM cannot detect a
clogged fuel injector, a sticking pintle, or that an
incorrect injector is installed.(*)
Fuel Requirements − Poor quality gasoline can
cause problems such as hard starting, stalling, and
stumble. Use of methanol-gasoline blends may re-
sult in starting and driveability problems. (See
individual symptoms and their definitions in Sec-
tion 6.0 (Glossary of Terms)).
PCM Grounds − The PCM cannot detect a poor
system ground. However, a diagnostic trouble code
may be stored in the PCM as a result of this
condition.
Throttle Body Air Flow − The PCM cannot
detect a clogged or restricted air cleaner inlet or
filter element.(*)
Exhaust System − The PCM cannot detect a
plugged, restricted, or leaking exhaust system.(*)
9
GENERAL INFORMATION