The power liftgate control module communicates
on the J1850 Programmable Communication Inter-
face (PCI) Bus Circuit. Therefore, the power liftgate
control module can generate and store its own Diag-
nostic Trouble Codes (DTC). The vehicles Body Con-
trol Module (BCM) receives and supplies messages tothe power liftgate control module via the PCI bus cir-
cuit. A diagnostic scan tool, such as the DRB IIItis
used to read and troubleshoot these Diagnostic Trou-
ble Codes (DTC). Refer to the Body Diagnostic Man-
ual for a complete list of diagnostic routines.
For additional information refer to Power Liftgate
Operation. For a complete system wiring schematic
refer to Wiring Diagrams. For system operation
instructions refer to the vehicles owner manual.
Refer to the Body section of the service manual
for additional information on liftgate components
such as the prop rods, hinges, door alignment and
striker alignment.
WARNING: BE CERTAIN TO READ ALL WARNINGS
AND CAUTIONS (NOTED BELOW) IN POWER LIFT-
GATE SYSTEM OPERATION BEFORE ATTEMPTING
ANY SERVICE OF THE POWER LIFTGATE SYSTEM
OR COMPONENTS.
OPERATION
With the push of a power liftgate open/close com-
mand switch (key fob or overhead console mounted) a
signal is sent out on the J1850 PCI Data Bus circuit.
This signal is detected at the body control module
(BCM). The BCM then sends a signal out on the
J1850 PCI Data Bus circuit to the power liftgate
module. The power liftgate module then signals the
power liftgate motor to start an open or close cycle,
depending on what position the liftgate is in open or
closed.
During a liftgate open or close cycle, if the power
liftgate module detects sufficient resistance to liftgate
travel, such as an obstruction in the liftgates path,
the power liftgate control module will immediately
stop the liftgate movement and reverse travel to the
full open or closed position. The ability for the power
liftgate module to detect resistance to liftgate travel
is accomplished by hall effect sensors, drive motor
speed and pinch sensors (tape switches).
The power liftgate control module has the ability to
learn. Anytime the liftgate is opened or closed using
the power liftgate system the module learns from its
cycle. If a replacement power liftgate component is
installed or a liftgate adjustment is made, the mod-
ule will relearn the effort and/or time required to
open or close the door. This learn cycle can be per-
formed with a Diagnostic Scan Tool, such as the DRB
IIItor with a complete cycle of the liftgate, using
any one of the command switches. Refer to Standard
Procedures in this section for detailed instructions.Fig. 2 KEY FOB
1 - Left Sliding Door Switch
2 - Right Sliding Door Switch
3 - Liftgate Switch
Fig. 3 LIFTGATE FUSE LOCATION
RSPOWER LIFTGATE SYSTEM8N-3
POWER LIFTGATE SYSTEM (Continued)
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The mirror switch allows the driver a manual con-
trol of whether the automatic dimming feature is
operational. When AUTO is selected a small Light-
Emitting Diode (LED), to the right of the mirror
switch, is illuminated. The automatic dimming fea-
ture will only operate when the ignition switch is in
the On position. The mirror also senses the backup
lamp circuit, and will automatically disable its self-
dimming feature whenever the transmission gear
selector is in the Reverse position.
NOTE: The mirror always defaults to an ON state
upon ignition.
The driver side automatic dimming mirror is stan-
dard with the automatic dimming inside mirror. The
signal to control the dimming of that mirror is gen-
erated by the automatic day/night inside rear view
mirror circuitry. That signal is then delivered to the
driver side outside rear view mirror on a hard wired
circuit.
The automatic day/night mirror cannot be
repaired. If faulty or damaged, the entire inside rear
view mirror assembly must be replaced.
DIAGNOSIS AND TESTING - AUTOMATIC DAY /
NIGHT MIRROR
For circuit descriptions and diagrams, refer to the
appropriate wiring information. The wiring informa-
tion includes wiring diagrams, proper wire and con-
nector repair procedures, details of wire harness
routing and retention, connector pin-out information
and location views for the various wire harness con-
nectors, splices and grounds.
(1) Check the fuse in the intelligent power module.
If OK, go to Step 2. If not OK, repair the shorted cir-
cuit or component as required and replace the faulty
fuse.
(2) Turn the ignition switch to the On position.
Check for battery voltage at the fuse in the intelli-
gent power module. If OK, go to Step 3. If not OK,
repair the open circuit to the ignition switch as
required.
(3) Unplug the wire harness connector from the
automatic day/night mirror. Check for battery voltage
at the fused ignition switch output circuit cavity of
the automatic day/night mirror wire harness connec-
tor. If OK, go to Step 4. If not OK, repair the open
circuit to the junction block as required.
(4) Turn the ignition switch to the Off position.
Check for continuity between the ground circuit cav-
ity of the automatic day/night mirror wire harness
connector and a good ground. There should be conti-
nuity. If OK, go to Step 5. If not OK, repair the cir-
cuit to ground as required.(5) Turn the ignition switch to the On position. Set
the parking brake. Place the transmission gear selec-
tor lever in the Reverse position. Check for battery
voltage at the backup lamp switch output circuit cav-
ity of the automatic day/night mirror wire harness
connector. If voltage is present, reinstall the auto-
matic day/night mirror wire harness connector and
go to Step 6. If not OK, repair the open circuit as
required.
(6) Place the transmission gear selector lever in
the Neutral position. Place the automatic day/night
mirror switch in the On (LED in the switch is
lighted) position. Cover the forward facing ambient
photocell sensor to keep out any ambient light.
NOTE: The ambient photocell sensor must be cov-
ered completely, so that no light reaches the sen-
sor. Use a finger pressed tightly against the sensor,
or cover the sensor completely with electrical tape.
(7) Shine a light into the rearward facing head-
lamp photocell sensor. The automatic day/night mir-
ror should darken. The automatic day/night mirror
should darken within 2 minutes if testing for the
first time. For immediate response, turn the vehicle
OFF and back ON with the forward-facing light sen-
sor still covered. This defeats the day-detect logic. If
OK, go to Step 8. If not OK, replace the faulty mirror
unit.
(8) With the mirror darkened, place the transmis-
sion gear selector lever in the Reverse position. The
automatic day/night mirror should return to its nor-
mal reflectance. If not OK, replace the faulty mirror
unit.
Bench testing both mirrors can be done, of care is
exercised. For an inside mirror, the pin closest to he
mount is 12V (+), the next is 12V (-). The third is
reverse override. The fourth is outside mirror (+),
and the fifth is outside mirror (-).Do not apply 12
volts to the fourth and fifth pins.With 12 volts
on pins 1 and 2, the mirror can be tested by blocking
the rear sensor and shining a light into the forward
sensor. For an outside mirror, there is a 2±pin con-
nector. Applying 1.2 volts will cause the mirror to
dim. If the mirror does not dim, the entire glass
assembly can be replaced just as it is when the glass
is broken.
WARNING: Do not apply 12 volts to the outside mir-
ror. Damage to the mirror will result.
8N - 48 POWER MIRRORSRS
AUTOMATIC DAY / NIGHT MIRROR (Continued)
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