Chrysler PT Cruiser 2001 Service Manual Supplement page 2054

8E - 2 ELECTRONIC CONTROL MODULES
HEATED SEAT MODULE (Continued)
When a driver or passenger heated seat switch
request signal is received by the heated seat module,
the module energizes the proper switch LED indica-
tor lamp (Lo or Hi) by pulling the LED driver circuit
to ground. This provides an indication to the vehicle
operator that the heated seat system is operating
and whether the Hi or Lo heat mode is selected. At
the same time, the heated seat module energizes the
heated seat sensor feed circuit and the sensor pro-
vides the module with a heat sense input indicating
the surface temperature of the selected seat cushion.
If the seat cushion surface temperature input is
below the temperature set point for the selected heat
mode, the heated seat module energizes an N-chan-
nel Field Effect Transistor (N-FET) within the mod-
ule. The N-FET switches battery current to the
heated seat elements in the selected seat cushion and
back. When the heated seat sensor input indicates
the correct temperature set point has been achieved,
the heated seat module de-energizes the N-FET
which switches off the battery current to the heated
seat elements. The heated seat module will continue
to cycle the N-FET as needed to maintain the
selected temperature set point.
If the heated seat module detects a heated seat
sensor value input that is out of range or a shorted
or open heated seat element circuit, it will automat-
ically de-energize the N-FET and switch off the bat-
tery current to the affected heated seat elements.
The heated seat module will also notify the vehicle
operator or the repair technician of this condition by
flashing the Hi and/or Lo LED indicator lamps in the
affected heated seat switch in a prescribed sequence
as a self-diagnostic feedback. Refer to Diagnosis and
Testing for the proper heated seat system diagnosis
and testing procedures.
DIAGNOSIS AND TESTING - HEATED SEAT
MODULE
Two heated seat modules are used on each vehicle,
one for each front seat. Refer to the appropriate wir-
ing information in Wiring Diagrams. The wiring
information includes wiring diagrams, proper wire
and connector repair procedures, further details on
wire harness routing and retention, as well as pin-
out and location views for the various wire harness
connectors, splices and grounds.
(1) If a heated seat fails to heat and one or both of
the LED indicator lamps on a heated seat switch
flash, refer to the heated seat system diagnosis and
testing procedures. If a heated seat heats, but one or
both LED indicator lamps on the heated seat switch
fail to operate, refer to the appropriate heated seat
switch diagnosis and testing procedure. If the heated
seat switch checks OK, go to Step 4. If both seats
(driver and passenger) fail to heat and the LED indi-
2001 PT CRUISER
cator lamps on the heated seat switches for both
seats fail to operate, refer to the heated seat relay
diagnosis and testing procedure. If the heated seat
relay checks OK, go to Step 2. If only one seat (driver
or passenger) fails to heat and the LED indicator
lamps on the heated seat switch for that seat fail to
operate, refer to the heated seat switch diagnosis and
testing procedure. If the heated seat switch checks
OK, go to Step 3. If a heated seat switch LED indi-
cator lamp remains illuminated after the heated seat
has been turned Off, go to Step 5.
(2) Disconnect and isolate the battery negative
cable. Disconnect the power seat wire harness con-
nector from the heated seat module connector recep-
tacle. Check for continuity between the ground
circuit cavity of the wire harness connector for the
heated seat module and a good ground. If OK, go to
Step 3. If not OK, repair the open ground circuit to
ground as required.
(3) Disconnect and isolate the battery negative
cable. Disconnect the power seat wire harness con-
nector from the heated seat module connector recep-
tacle. Disconnect the power seat wire harness
connector(s) from the connector receptacle(s) of the
inoperative heated seat switch(es). Check for continu-
ity between the inoperative driver and/or passenger
seat heater switch MUX circuit cavities of the
power seat wire harness connector(s) for the inopera-
tive heated seat switch and the power seat wire har-
ness connector for the heated seat module. There
should be continuity. If OK, replace the faulty heated
seat module. If not OK, repair the open driver and/or
passenger seat heater switch MUX circuit as
required.
(4) Disconnect and isolate the battery negative
cable. Disconnect the power seat wire harness con-
nector from the heated seat module connector recep-
tacle. Disconnect the power seat wire harness
connector(s) from the connector receptacle(s) of the
heated seat switch(es) with the inoperative LED indi-
cator lamp(s). Check for continuity between the inop-
erative driver and/or passenger seat high and/or low
heat LED driver circuit cavities of the power seat
wire harness connector(s) for the heated seat switch-
(es) and the power seat wire harness connector for
the heated seat module. There should be continuity.
If OK, replace the faulty heated seat module. If not
OK, repair the open driver or passenger seat high or
low heat LED driver circuit as required.
(5) Disconnect and isolate the battery negative
cable. Disconnect the power seat wire harness con-
nector from the heated seat module connector recep-
tacle. Disconnect the power seat wire harness
connector(s) from the connector receptacle(s) of the
heated seat switch(es) with the inaccurate LED indi-
cator lamp(s). Check for continuity between the inop-
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