2003 JEEP GRAND CHEROKEE Codes

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)

EMISSIONS CONTROL
TABLE OF CONTENTS
page page
EMISSIONS CONTROL
DESCRIPTION
DESCRIPTION - EMISSION CONTROL
SYSTEM.............................1
DESCRIPTION - STATE DISPLAY TEST
MODE...............................2
DESCRIPTION - CIRCUIT ACTUATION TEST
MODE...............................2
DESCRIPTION - DIAGNOSTIC TROUBLE
CODES..............................2DESCRIPTION - TASK MANAGER.........17
DESCRIPTION - MONITORED SYSTEMS . . . 17
DESCRIPTION - TRIP DEFINITION........19
DESCRIPTION - COMPONENT MONITORS . . 19
DESCRIPTION - NON-MONITORED
CIRCUITS...........................20
DESCRIPTION - HIGH AND LOW LIMITS . . . 20
DESCRIPTION - LOAD VALUE...........20
OPERATION - TASK MANAGER............21
EVAPORATIVE EMISSIONS................24
EMISSIONS CONTROL
DESCRIPTION
DESCRIPTION - EMISSION CONTROL SYSTEM
The Powertrain Control Module (PCM) monitors
many different circuits in the fuel injection, ignition,
emission and engine systems. If the PCM senses a prob-
lem with a monitored circuit often enough to indicate an
actual problem, it stores a Diagnostic Trouble Code
(DTC) in the PCM's memory. If the code applies to a
non-emissions related component or system, and the
problem is repaired or ceases to exist, the PCM cancels
the code after 40 warm-up cycles. Diagnostic trouble
codes that affect vehicle emissions illuminate the Mal-
function Indicator (check engine) Lamp. Refer to Mal-
function Indicator Lamp in this section.
Certain criteria must be met before the PCM
stores a DTC in memory. The criteria may be a spe-
cific range of engine RPM, engine temperature,
and/or input voltage to the PCM.
The PCM might not store a DTC for a monitored cir-
cuit even though a malfunction has occurred. This may
happen because one of the DTC criteria for the circuit
has not been met.For example
,assume the diagnostic
trouble code criteria requires the PCM to monitor the
circuit only when the engine operates between 750 and
2000 RPM. Suppose the sensor's output circuit shorts to
ground when engine operates above 2400 RPM (result-
ing in 0 volt input to the PCM). Because the condition
happens at an engine speed above the maximum thresh-
old (2000 rpm), the PCM will not store a DTC.
There are several operating conditions for which
the PCM monitors and sets DTC's. Refer to Moni-
tored Systems, Components, and Non-Monitored Cir-
cuits in this section.Technicians must retrieve stored DTC's by connect-
ing the DRB scan tool (or an equivalent scan tool) to
the 16±way data link connector (Fig. 1).
NOTE: Various diagnostic procedures may actually
cause a diagnostic monitor to set a DTC. For
instance, pulling a spark plug wire to perform a
spark test may set the misfire code. When a repair
is completed and verified, connect the DRB scan
tool to the 16±way data link connector to erase all
DTC's and extinguish the MIL (check engine lamp).Fig. 1 Data Link (Diagnostic) Connector Location
1 - INSTRUMENT PANEL LOWER/LEFT EDGE
2 - DATA LINK CONNECTOR
WJEMISSIONS CONTROL 25 - 1

DESCRIPTION - STATE DISPLAY TEST MODE
The switch inputs to the Powertrain Control Mod-
ule (PCM) have two recognized states; HIGH and
LOW. For this reason, the PCM cannot recognize the
difference between a selected switch position versus
an open circuit, a short circuit, or a defective switch.
If the State Display screen shows the change from
HIGH to LOW or LOW to HIGH, assume the entire
switch circuit to the PCM functions properly. Connect
the DRB scan tool to the data link connector and
access the state display screen. Then access either
State Display Inputs and Outputs or State Display
Sensors.
DESCRIPTION - CIRCUIT ACTUATION TEST
MODE
The Circuit Actuation Test Mode checks for proper
operation of output circuits or devices the Powertrain
Control Module (PCM) may not internally recognize.
The PCM attempts to activate these outputs and
allow an observer to verify proper operation. Most of
the tests provide an audible or visual indication of
device operation (click of relay contacts, fuel spray,
etc.). Except for intermittent conditions, if a device
functions properly during testing, assume the device,
its associated wiring, and driver circuit work cor-
rectly. Connect the DRB scan tool to the data link
connector and access the Actuators screen.
DESCRIPTION - DIAGNOSTIC TROUBLE CODES
A Diagnostic Trouble Code (DTC) indicates the
PCM has recognized an abnormal condition in the
system.Remember that DTC's are the results of a sys-
tem or circuit failure, but do not directly iden-
tify the failed component or components.
NOTE: For a list of DTC's, refer to the charts in this
section.
BULB CHECK
Each time the ignition key is turned to the ON
position, the malfunction indicator (check engine)
lamp on the instrument panel should illuminate for
approximately 2 seconds then go out. This is done for
a bulb check.
OBTAINING DTC'S USING DRB SCAN TOOL
(1) Connect the DRB scan tool to the data link
(diagnostic) connector. This connector is located in
the passenger compartment; at the lower edge of
instrument panel; near the steering column.
(2) Turn the ignition switch on and access the
ªRead Faultº screen.
(3) Record all the DTC's and ªfreeze frameº infor-
mation shown on the DRB scan tool.
(4) To erase DTC's, use the ªErase Trouble Codeº
data screen on the DRB scan tool.Do not erase any
DTC's until problems have been investigated
and repairs have been performed.
(M)Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was recorded
(depending if required by CARB and/or EPA). MIL is displayed as an engine icon on instrument panel.
(G)Generator lamp illuminated
Generic Scan
Tool P-CodeDRB Scan Tool Display Brief Description of DTC
P0030 (M) 1/1 O2 Sensor Heater Circuit
MalfunctionProblem detected in oxygen sensor heater relay circuit.
P0031 (M) 1/1 O2 Sensor Heater Circuit Low Problem detected in oxygen sensor heater relay circuit.
P0032 (M) 1/1 O2 Sensor Heater Circuit High Problem detected in oxygen sensor heater relay circuit.
P0036 (M) 1/2 O2 Sensor Heater Circuit
MalfunctionProblem detected in oxygen sensor heater relay circuit.
P0037 (M) 1/2 O2 Sensor Heater Circuit Low Problem detected in oxygen sensor heater relay circuit.
P0038 (M) 1/2 O2 Sensor Heater Circuit High Problem detected in oxygen sensor heater relay circuit.
P0043 (M) 1/3 O2 Sensor Heater Circuit Low Problem detected in oxygen sensor heater relay circuit.
P0044 (M) 1/3 O2 Sensor Heater Circuit High Problem detected in oxygen sensor heater relay circuit.
P0051 (M) 2/1 O2 Sensor Heater Circuit Low Problem detected in oxygen sensor heater relay circuit.
P0052 (M) 2/1 O2 Sensor Heater Circuit High Problem detected in oxygen sensor heater relay circuit.
25 - 2 EMISSIONS CONTROLWJ
EMISSIONS CONTROL (Continued)

DESCRIPTION - TASK MANAGER
The PCM is responsible for efficiently coordinating
the operation of all the emissions-related compo-
nents. The PCM is also responsible for determining if
the diagnostic systems are operating properly. The
software designed to carry out these responsibilities
is referred to as the 'Task Manager'.
DESCRIPTION - MONITORED SYSTEMS
There are new electronic circuit monitors that
check fuel, emission, engine and ignition perfor-
mance. These monitors use information from various
sensor circuits to indicate the overall operation of the
fuel, engine, ignition and emission systems and thus
the emissions performance of the vehicle.
The fuel, engine, ignition and emission systems
monitors do not indicate a specific component prob-
lem. They do indicate that there is an implied prob-
lem within one of the systems and that a specific
problem must be diagnosed.
If any of these monitors detect a problem affecting
vehicle emissions, the Malfunction Indicator Lamp
(MIL) will be illuminated. These monitors generate
Diagnostic Trouble Codes that can be displayed with
the MIL or a scan tool.
The following is a list of the system monitors:
²Misfire Monitor
²Fuel System Monitor
²Oxygen Sensor Monitor
²Oxygen Sensor Heater Monitor
²Catalyst Monitor
²Leak Detection Pump Monitor (if equipped)
All these system monitors require two consecutive
trips with the malfunction present to set a fault.
Refer to the appropriate Powertrain Diagnos-
tics Procedures manual for diagnostic proce-
dures.
The following is an operation and description of
each system monitor:
OXYGEN SENSOR (O2S) MONITOR
Effective control of exhaust emissions is achieved
by an oxygen feedback system. The most important
element of the feedback system is the O2S. The O2S
is located in the exhaust path. Once it reaches oper-
ating temperature 300É to 350ÉC (572É to 662ÉF), the
sensor generates a voltage that is inversely propor-
tional to the amount of oxygen in the exhaust. The
information obtained by the sensor is used to calcu-
late the fuel injector pulse width. This maintains a
14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio,
the catalyst works best to remove hydrocarbons (HC),
carbon monoxide (CO) and nitrogen oxide (NOx) from
the exhaust.
The O2S is also the main sensing element for the
Catalyst and Fuel Monitors.The O2S can fail in any or all of the following
manners:
²slow response rate
²reduced output voltage
²dynamic shift
²shorted or open circuits
Response rate is the time required for the sensor to
switch from lean to rich once it is exposed to a richer
than optimum A/F mixture or vice versa. As the sen-
sor starts malfunctioning, it could take longer to
detect the changes in the oxygen content of the
exhaust gas.
The output voltage of the O2S ranges from 0 to 1
volt. A good sensor can easily generate any output
voltage in this range as it is exposed to different con-
centrations of oxygen. To detect a shift in the A/F
mixture (lean or rich), the output voltage has to
change beyond a threshold value. A malfunctioning
sensor could have difficulty changing beyond the
threshold value.
OXYGEN SENSOR HEATER MONITOR
If there is an oxygen sensor (O2S) shorted to volt-
age DTC, as well as a O2S heater DTC, the O2S
fault MUST be repaired first. Before checking the
O2S fault, verify that the heater circuit is operating
correctly.
Effective control of exhaust emissions is achieved
by an oxygen feedback system. The most important
element of the feedback system is the O2S. The O2S
is located in the exhaust path. Once it reaches oper-
ating temperature 300É to 350ÉC (572 É to 662ÉF), the
sensor generates a voltage that is inversely propor-
tional to the amount of oxygen in the exhaust. The
information obtained by the sensor is used to calcu-
late the fuel injector pulse width. This maintains a
14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio,
the catalyst works best to remove hydrocarbons (HC),
carbon monoxide (CO) and nitrogen oxide (NOx) from
the exhaust.
The voltage readings taken from the O2S sensor
are very temperature sensitive. The readings are not
accurate below 300ÉC. Heating of the O2S sensor is
done to allow the engine controller to shift to closed
loop control as soon as possible. The heating element
used to heat the O2S sensor must be tested to ensure
that it is heating the sensor properly.
The O2S sensor circuit is monitored for a drop in
voltage. The sensor output is used to test the heater
by isolating the effect of the heater element on the
O2S sensor output voltage from the other effects.
LEAK DETECTION PUMP MONITOR (IF EQUIPPED)
The leak detection assembly incorporates two pri-
mary functions: it must detect a leak in the evapora-
WJEMISSIONS CONTROL 25 - 17
EMISSIONS CONTROL (Continued)

an associated limp in will take two trips to illumi-
nate the MIL.
Refer to the Diagnostic Trouble Codes Description
Charts in this section and the appropriate Power-
train Diagnostic Procedure Manual for diagnostic
procedures.
DESCRIPTION - NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems and conditions that could have malfunctions
causing driveability problems. The PCM might not
store diagnostic trouble codes for these conditions.
However, problems with these systems may cause the
PCM to store diagnostic trouble codes for other sys-
tems or components. For example, a fuel pressure
problem will not register a fault directly, but could
cause a rich/lean condition or misfire. This could
cause the PCM to store an oxygen sensor or misfire
diagnostic trouble code
FUEL PRESSURE
The fuel pressure regulator controls fuel system
pressure. The PCM cannot detect a clogged fuel
pump inlet filter, clogged in-line fuel filter, or a
pinched fuel supply or return line. However, these
could result in a rich or lean condition causing the
PCM to store an oxygen sensor or fuel system diag-
nostic trouble code.
SECONDARY IGNITION CIRCUIT
The PCM cannot detect an inoperative ignition coil,
fouled or worn spark plugs, ignition cross firing, or
open spark plug cables.
CYLINDER COMPRESSION
The PCM cannot detect uneven, low, or high engine
cylinder compression.
EXHAUST SYSTEM
The PCM cannot detect a plugged, restricted or
leaking exhaust system, although it may set a fuel
system fault.
FUEL INJECTOR MECHANICAL MALFUNCTIONS
The PCM cannot determine if a fuel injector is
clogged, the needle is sticking or if the wrong injectoris installed. However, these could result in a rich or
lean condition causing the PCM to store a diagnostic
trouble code for either misfire, an oxygen sensor, or
the fuel system.
EXCESSIVE OIL CONSUMPTION
Although the PCM monitors engine exhaust oxygen
content when the system is in closed loop, it cannot
determine excessive oil consumption.
THROTTLE BODY AIRFLOW
The PCM cannot detect a clogged or restricted air
cleaner inlet or filter element.
VACUUM ASSIST
The PCM cannot detect leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices. However, these could cause the PCM
to store a MAP sensor diagnostic trouble code and
cause a high idle condition.
PCM SYSTEM GROUND
The PCM cannot determine a poor system ground.
However, one or more diagnostic trouble codes may
be generated as a result of this condition. The mod-
ule should be mounted to the body at all times, also
during diagnostic.
PCM CONNECTOR ENGAGEMENT
The PCM may not be able to determine spread or
damaged connector pins. However, it might store
diagnostic trouble codes as a result of spread connec-
tor pins.
DESCRIPTION - HIGH AND LOW LIMITS
The PCM compares input signal voltages from each
input device with established high and low limits for
the device. If the input voltage is not within limits
and other criteria are met, the PCM stores a diagnos-
tic trouble code in memory. Other diagnostic trouble
code criteria might include engine RPM limits or
input voltages from other sensors or switches that
must be present before verifying a diagnostic trouble
code condition.
DESCRIPTION - LOAD VALUE
ENGINE IDLE/NEUTRAL 2500 RPM/NEUTRAL
All Engines 2% to 8% of Maximum Load 9% to 17% of Maximum Load
25 - 20 EMISSIONS CONTROLWJ
EMISSIONS CONTROL (Continued)