2002 JEEP GRAND CHEROKEE Control

Both the manual A/C Heater control panel and the
AZC control panel are serviced only as complete
units and cannot be repaired. If faulty or damaged,
the entire control panel unit must be replaced.
DIAGNOSIS AND TESTING - AUTOMATIC ZONE
CONTROL SYSTEM
The Automatic Zone Control (AZC) control module
has a system self-diagnostic mode which continuously
monitors various parameters during normal system
operation. If a system fault is detected, a current and
historical fault is recorded. When the current fault is
cleared, the historical fault remains until reset (man-
ually or automatically). Both the current and histor-
ical fault codes can be accessed through either the
front panel, or over the Programmable Communica-
tions Interface (PCI) bus using a DRBIIItscan tool,
and the appropriate diagnostic information.
The AZC control module is capable of three differ-
ent types of self-diagnostic tests, as follows:
²Fault Code Tests
²Input Circuit Tests
²Output Circuit/Actuator Tests
The information that follows describes:
²How to read the self-diagnostic display
²How to enter the AZC control module self-diag-
nostic test mode
²How to select the self-diagnostic test types
²How to perform the different tests
ENTERING THE AZC SELF-DIAGNOSTIC MODE
To enter the AZC self-diagnostic mode, perform the
following:
(1) Depress the a/c and recirc buttons at the same
time and hold. Rotate the left temperature control
knob clockwise (CW) one detent.
(2) If you continue to keep the a/c and recirc but-
tons depressed, the AZC control module will perform
a Segment Test of the Vacuum Fluorescent (VF) dis-
play. In the Segment Test you should see all of the
display segments illuminate as long as both buttons
are held. If a display segment fails to illuminate, the
vacuum fluorescent display is faulty and the a/c
heater control must be replaced.
(3) After viewing the Segment Test, release the
A/C and Recirc buttons and the display will clear
momentarily.Ifa0isdisplayed, then no faults
are set in the system.Should there be any faults,
either9current9or9historical9, all fault codes will be
displayed in ascending numerical sequence (note no
effort is made to display fault codes in chronological
order). Each fault code is displayed for one second
before the next code is displayed. Once all fault codes
have been displayed, the system will then repeat the
fault code numbers. This will continue until the left
side set temperature control is moved at least onedetent position in the CW direction or the ignition is
turned9OFF9.
FAULT CODE TESTS
Fault codes are two-digit numbers that identify a
circuit that is malfunctioning. There are two differ-
ent kinds of fault codes.
1.Current Fault Codes- Current means the
fault is present right now. There are two types of cur-
rent faults: input faults, and system faults.
2.Historical Fault Codes- Historical or stored
means that the fault occurred previously, but is not
present right now. A majority of historical fault codes
are caused by intermittent wire harness or wire har-
ness connector problems.
CURRENT FAULT CODES
Input faults 01 = IR thermister circuit
open
02 = IR thermister circuit
shorted
03 = Fan pot shorted
04 = Fan pot open
05 = Mode pot shorted
06 = Mode pot open
07 = IR sensor delta too
large
08 = Reserved
09 = Reserved
10 = One of four motor
drivers has drive9A9
shorted to ground
11 = Engine air intake
temperature Buss
message missing
12 = Country code Buss
message missing
24 - 18 CONTROLSWJ
A/C HEATER CONTROL (Continued)

CURRENT FAULT CODES
System Faults 13 = Mode motor not
responding
14 = AI (Recirc) motor
not responding
15 = Left temperature
door not responding
16 = Right temperature
door not responding
17 = Mode door travel
range too small
18 = Mode door travel
range too large
19 = AI (Recirc) door
travel too small
20 = AI (Recirc) door
travel too large
21 = Left temperature
door travel too small
22 = Left temperature
door travel too large
23 = Right temperature
door travel too small
24 = Right temperature
door travel too large
25 = Calibration check
sum error
26 = Engine coolant temp
bus message missing
27 = Vehicle speed bus
message missing
28 = Engine RPM bus
message missing
29 = OAT bus message
missing
30 = Display intensity bus
message missing
31 = VIN number bus
message missing
32 = Raw OAT bus
message missing
WJCONTROLS 24 - 19
A/C HEATER CONTROL (Continued)

HISTORICAL FAULT CODES
Input faults 33 = IR thermister circuit was open
34 = IR thermister circuit was shorted
35 = Fan pot was shorted
36 = Fan pot was open
37 = Mode pot was shorted
38 = Mode pot was open
39 = IR sensor delta was too large
40 = Reserved
41 = Reserved
42 = One of four motor drivers had drive9A9shorted to
ground
43 = Engine air intake temperature Buss message
missing
44 = Country code Buss message missing
System Faults 45 = Mode motor was not responding
46 = AI (Recirc) motor was not responding
47 = Left temperature door was not responding
48 = Right temperature door was not responding
49 = Mode door travel range too small
50 = Mode door travel range too large
51 = AI (Recirc) door travel range too small
52 = AI (Recirc) door travel range too large
53 = Left temperature door travel too small
54 = Left temperature door travel too large
55 = Right temperature door travel too small
56 = Right temperature door travel too large
57 = Calibration check sum error
58 = Engine coolant temp bus message missing
59 = Vehicle speed bus message missing
60 = Engine RPM bus message missing
61 = OAT bus message missing
62 = Display intensity bus message missing
63 = VIN number bus message missing
64 = Raw OAT bus message was missing
65 = Reserved
66 = Reserved
67 = Reserved
NOTE: A battery disconnect will erase all faults
stored in Random Access Memory (RAM) of the
AZC control module. It is recommended that all
faults be recorded before they are erased.RETRIEVING FAULT CODES
(1) To begin the fault code tests, depress the A/C
and Recirc buttons at the same time and rotate the
left temperature control knob clockwise (CW) one
detent, then release the push-button.
24 - 20 CONTROLSWJ
A/C HEATER CONTROL (Continued)

(2)If there are no fault codes, the ª00º dis-
play value will remain in the VF window.Should
there be any codes, each will be displayed for one
second in ascending numerical sequence (note: no
effort is made to display faults in the order they
occurred). The left side set temperature display will
be blanked and the right side set temperature dis-
play will indicate current and historical codes (8 his-
torical max) presently active. Once all codes have
been displayed, the system will repeat the fault code
numbers. This will continue until the left side set
temperature control is moved at least one detent
position in either direction, by pressing both the A/C
and Recirc buttons at the same time, or the ignition
is turned off. Record all of the fault codes, then see
the Current and Historical Fault Code charts for the
descriptions.
CLEARING FAULT CODES
Current faults cannot be electronically cleared.
Repair must be made to the system to eliminate the
fault causing code. Historical fault codes can be
cleared manually, or automatically. To clear a histor-
ical fault manually, depress and hold either the A/C
or Recirc button for at least three seconds while the
display is in the fault code mode of operation. Histor-
ical fault codes are cleared automatically when the
corresponding current fault code has been cleared,
and has remained cleared for a number of ignition
cycles. The faults have been cleared when two hori-
zontal bars appear in the Test Selector display.
EXITING SELF-DIAGNOSTIC MODE
The self-diagnostic mode can be exited by pressing
both the A/C and Recirc buttons at the same time, or
turning off the ignition.
MONITOR CURRENT PARAMETERS
While in the display fault code mode of operation,
current system parameters can also be monitored
and/or forced. Rotating the left side set temperature
control clockwise will increase the pointer number
while rotating the control counter clockwise will
decrease the pointer number. Rotating the right set
temperature control will have no impact on pointer
value or the value of the parameter being monitored.
Once the desired pointer number has been selected,
pressing either the AC or Recirc buttons will display
the current value of the selected parameter.The
right side set temperature display is only capa-
ble of displaying only values ranging from 0 to
99, the left side set temperature display is used
for values greater than 99. If the value is less
than 99, the left side set temperature display
remains blanked.While a parameter is being over-
ridden, the system will continue to function normallyexcept for the parameter which is being manually
controlled.
For values < 0, the9G9segment in the left side set
temperature Most Significant Digit (MSD)(or left-
most number in the pair) will be used to indicate a
negative number. For values between -01 to -99 the
Least Significant Digit (LSD)(or right-most number
of the pair) in the left side set temperature will
remain blank. System control of parameter being dis-
played can be overridden by rotating the right set
temperature control in either direction. Rotating the
right temperature control in the CW direction, the
selected parameter value is overridden and incre-
mented beginning at the value which was being dis-
played. Rotating the right temperature control in the
CCW direction, the selected parameter value is over-
ridden and decremented beginning at the value
which was being displayed. The rate at which incre-
menting and decrement occurs is one unit value per
set temperature detent position.
HVAC SYSTEM POINTER
Pointer
NumberDESCRIPTION Value
Displayed
01 A/C Enable 0 or 1
0=
disabled
1=
enabled
02 Final fan PWM duty cycle 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
03 Left NPRG * 0 to 255
* NPRG equals a calculated number based on outside
and in-vehicle conditions. This value is used by the
AZC to position the Mode motor, Air Inlet motor, and
control blower motor speed.
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
04 Right NPRG 0 to 255
WJCONTROLS 24 - 21
A/C HEATER CONTROL (Continued)

HVAC SYSTEM POINTER
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
05 Avg NPRG 0 TO
255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
06 Primary control side 0 or 1
0 = left 1
= right
07 EE Check sum (calculated) 0 to 255
08 Target intensity (in % ON time) 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
09 Not Used 0 to 0
10 Not Used 0 to 0
11 Right NINC * 0 to 255
* NINC equals a calculated number based on the IR
sensor and IR thermistor values used to calculate the
NPRG.
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
12 Left NINC 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
13 Right NMIX * 0 to 255
* NMIX equals a calculated number based on outside
and in-vehicle conditions used by the AZC to position
the Temperature motors.HVAC SYSTEM POINTER
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
14 Left NMIX 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CW = decrease
15 Not Used 0 to 0
16 Not Used 0 to 0
17 Reserved
18 Reserved
19 Reserved
MODE VALUE POINTER
Pointer
NumberDESCRIPTION Value
Displayed
20 mode range in delta counts 0 to
9999
21 Current mode position (in
counts)0to
9999
22 mode target position in ratio 0 to 255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
23 mode target position in counts 0 to
9999
24 Not Used 0 to 0
25 number of valve moves since
last index0to
9999
26 Not Used 0 to 0
27 Not Used 0 to 0
28 Not Used 0 to 0
29 mode motor state 0 to 5
0 = in position, 1 = moving
toward panel, 2 = moving
toward defrost, 3 = searching
range, 4 = stalled moving
toward panel, 5 = stalled
moving toward defrost
24 - 22 CONTROLSWJ
A/C HEATER CONTROL (Continued)

LEFT SIDE TEMPERATURE POINTER
Pointer
NumberDESCRIPTION Value
Displayed
30 Left side temp range in delta
counts0to
9999
31 Current left side temp position
(in counts)0to
9999
32 Left side temp target position
(in ratio)0to255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
33 Left side temp target in counts 0 to
9999
34 Not used 0 to 0
35 number of valve moves since
last index0to
9999
36 Not used 0 to 0
37 Not used 0 to 0
38 Not used 0 to 0
39 Left side temp motor state 0 to 5
0 = in position, 1 = moving
toward panel, 2 = moving
toward defrost, 3 = searching
range, 4 = stalled moving
toward panel, 5 = stalled
moving toward defrost
RIGHT SIDE TEMPERATURE POINTER
Pointer
NumberDESCRIPTION Value
Displayed
40 Right side temp range in delta
counts0to
9999
41 Current right side temp
position (in counts)0to
9999
42 Right side temp target position
(in ratio)0to255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
43 Right side temp target in
counts0to
9999
44 Not used 0 to 0
RIGHT SIDE TEMPERATURE POINTER
45 number of valve moves since
last index0to
9999
46 Not used 0 to 0
47 Not used 0 to 0
48 Not used 0 to 0
49 Right side temp motor state 0 to 5
0 = in position, 1 = moving
toward panel, 2 = moving
toward defrost, 3 = searching
range, 4 = stalled moving
toward panel, 5 = stalled
moving toward defrost
AIR INLET POINTER
Pointer
NumberDESCRIPTION Value
Displayed
50 Air inlet range (in counts) 0 to
9999
51 Current air inlet position (in
counts)0to
9999
52 Air inlet target position (in
ratio)0to255
While the value of this pointer
is being displayed, turning the
right set temperature control
either direction will manually
control the value. CW =
increase; CCW = decrease
53 Air inlet target in counts 0 to
9999
54 Not used 0 to 0
55 number of motor moves since
last index0to
9999
56 Not used 0 to 0
57 Not used 0 to 0
58 Not used 0 to 0
59 Air inlet motor state 0 to 5
0 = in position, 1 = moving
toward panel, 2 = moving
toward defrost, 3 = searching
range, 4 = stalled moving
toward panel, 5 = stalled
moving toward defrost
60 Reserved
61 Actual Outside Air Temp (in
degrees F)-40 to
215
62 Not used 0 to 0
WJCONTROLS 24 - 23
A/C HEATER CONTROL (Continued)

AIR INLET POINTER
63 Engine Intake Air Temperature
(in degrees F)-40 to
215
64 Vehicle speed in MPH 0 to 255
65 Engine RPM/100 -0 to 82
66 Engine Coolant Temp - 40 (in
degrees F)-40 to
215
67 Country Code 0 to 255
68 Not used 0 to 0
69 Not used 0 to 0
IR SENSOR POINTER
Pointer
NumberDESCRIPTION Value
Displayed
70 Thermistor temp (in degrees) -40 to
215
71 Left side sensor A/D (filtered) 0 to 255
72 Right side sensor A/D (filtered) 0 to 255
73 Left side temp (in degrees F) -40 to
140
74 Right side temp (in degrees F) -40 to
140
75 Not used 0 to 0
76 Not used 0 to 0
77 Not used 0 to 0
78 Not used 0 to 0
79 Not used 0 to 0
IDENTIFICATION POINTER
Pointer
NumberDESCRIPTION Value
Displayed
80 ROM bit pattern number (digits
1,2,3 & 4)0to
9999
81 ROM bit pattern number (digits
5,6,7 & 8)0to
9999
82 CAL bit pattern number (digits
1,2,3 & 4)0to
9999
83 CAL bit pattern number (digits
5,6,7 & 8)0to
9999
84 Not used 0 to 0
85 Not used 0 to 0
86 Not used 0 to 0
87 Not used 0 to 0
88 Not used 0 to 0
89 Not used 0 to 0
OUTPUT CIRCUIT/ACTUATOR TESTS
In the Output Circuit/Actuator Test mode, the out-
put circuits can be viewed, monitored, overridden,
and tested. If a failure occurs in an output circuit,
test the circuit by overriding the system. Test the
actuator through its full range of operation.
(1) To begin the Output Circuit/Actuator Tests you
must be in the Select Test mode.
(2) With a ª00º value displayed in the Test Selector
and no stick man, turn the rotary temperature con-
trol knob until the test number you are looking for
appears in the Test Selector display. See the Circuit
Testing charts for a listing of the test numbers, test
items, test types, system tested, and displayed val-
ues.
(3) To see the output value, depress the a/c or
recirc button. The values displayed will represent the
output from the AZC control module.
(4) To enter the actuator test, depress the a/c or
recirc button. Then, rotate the right temperature set
knob to the desired position.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the center upper, and center lower
bezels from the instrument panel. Refer to Instru-
ment Panel System for the procedures.
(3) Remove the 4 screws that secure the a/c heater
control to the instrument panel (Fig. 13).
(4) Pull the a/c heater control assembly away from
the instrument panel far enough to access the con-
nections on the back of the control.
(5) Unplug the wire and/or vacuum harness con-
nectors from the back of the a/c heater control (Fig.
14).
(6) Remove the a/c heater control from the instru-
ment panel.
24 - 24 CONTROLSWJ
A/C HEATER CONTROL (Continued)

INSTALLATION
(1) Plug the wire harness and/or vacuum harness
connectors into the back of the a/c heater control.
(2) Position the a/c heater control in the instru-
ment panel and secure it with 4 screws. Tighten the
screws to 2.2 N´m (20 in. lbs.).
(3) Reinstall the center upper, and center lower
bezels onto the instrument panel. Refer to Instru-
ment Panel System for the procedures.
(4) Connect the battery negative cable.
A/C PRESSURE TRANSDUCER
DESCRIPTION
The A/C pressure transducer is installed on a fit-
ting located on the refrigerant discharge line near
the condenser. An internally threaded hex fitting on
the transducer connects it to the externally threaded
Schrader-type fitting on the discharge line. A rubber
O-ring seals the connection between the transducer
and the discharge line fitting. Three terminals within
a molded plastic connector receptacle on the top of
the transducer connect it to the vehicle electrical sys-
tem through a take out and connector of the head-
lamp and dash wire harness.
The A/C pressure transducer cannot be adjusted or
repaired and if faulty or damaged, it must be
replaced.
OPERATION
The A/C pressure transducer monitors the pres-
sures in the high side of the refrigerant system
through its connection to a fitting on the discharge
line. The transducer will change its internal resis-
tance in response to the pressures it monitors. The
Powertrain Control Module (PCM) provides a five
volt reference signal and a sensor ground to the
transducer, then monitors the output voltage of the
transducer on a sensor return circuit to determine
refrigerant pressure. The PCM is preporgrammed to
respond to this and other sensor inputs by controlling
the operation of the air conditioning compressor
clutch and the radiator cooling fan to help optimize
air conditioning system performance and to protect
the system components from damage. The A/C pres-
sure transducer input to the PCM will also prevent
the air conditioning compressor clutch from engaging
when the ambient temperatures are below about
0.556É C (33É F) due to the pressure/temperature
relationship of the refrigerant. The Schrader-type
valve in the liquid line fitting permits the A/C pres-
sure transducer to be removed or installed without
distrubing the refrigerant in the system. The A/C
pressure transducer is diagnosed using the DRBIIIt
scan tool. Refer to the appropriate diagnostic infor-
mation.
Fig. 13 A/C HEATER CONTROL REMOVE/INSTALL
1 - MOUNTING SCREW TABS
Fig. 14 A/C HEATER CONTROL CONNECTIONS
1 - MODE SWITCH
2 - ELECTRICAL CONNECTIONS
3 - VACUUM HARNESS
WJCONTROLS 24 - 25
A/C HEATER CONTROL (Continued)