2002 JEEP GRAND CHEROKEE Engine ground

The other two heater elements (downstream sen-
sors 1/2 and 2/2) are controlled by the downstream
heater relay through output signals from the PCM.
To avoid a large simultaneous current surge, power
is delayed to the 2 downstream heater elements by
the PCM for approximately 2 seconds.
REMOVAL
(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
(1) Install relay to PDC.
(2) Install cover to PDC.
O2S SENSOR
DESCRIPTION
The Oxygen Sensors (O2S) are attached to, and
protrude into the vehicle exhaust system. Depending
on the emission package, the vehicle may use a total
of either 2 or 4 sensors.
Federal Emissions Package:Two sensors are
used: upstream (referred to as 1/1) and downstream
(referred to as 1/2). With this emission package, the
upstream sensor (1/1) is located just before the main
catalytic convertor. The downstream sensor (1/2) is
located just after the main catalytic convertor.
4.7L V-8 With California Emissions Package:
On this emissions package, 4 sensors are used: 2
upstream (referred to as 1/1 and 2/1) and 2 down-
stream (referred to as 1/2 and 2/2). With this emis-
sion package, the right upstream sensor (2/1) is
located in the right exhaust downpipe just before the
mini-catalytic convertor. The left upstream sensor
(1/1) is located in the left exhaust downpipe just
before the mini-catalytic convertor. The right down-
stream sensor (2/2) is located in the right exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor. The left down-
stream sensor (1/2) is located in the left exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor.
4.0L 6±Cylinder With California Emissions
Package:On this emissions package, 4 sensors are
used: 2 upstream (referred to as 1/1 and 2/1) and 2
downstream (referred to as 1/2 and 2/2). With this
emission package, the rear/upper upstream sensor
(2/1) is located in the exhaust downpipe just beforethe rear mini-catalytic convertor. The front/upper
upstream sensor (1/1) is located in the exhaust down-
pipe just before the front mini-catalytic convertor.
The rear/lower downstream sensor (2/2) is located in
the exhaust downpipe just after the rear mini-cata-
lytic convertor, and before the main catalytic conver-
tor. The front/lower downstream sensor (1/2) is
located in the exhaust downpipe just after the front
mini-catalytic convertor, and before the main cata-
lytic convertor.
OPERATION
An O2 sensor is a galvanic battery that provides
the PCM with a voltage signal (0-1 volt) inversely
proportional to the amount of oxygen in the exhaust.
In other words, if the oxygen content is low, the volt-
age output is high; if the oxygen content is high the
output voltage is low. The PCM uses this information
to adjust injector pulse-width to achieve the
14.7±to±1 air/fuel ratio necessary for proper engine
operation and to control emissions.
The O2 sensor must have a source of oxygen from
outside of the exhaust stream for comparison. Cur-
rent O2 sensors receive their fresh oxygen (outside
air) supply through the O2 sensor case housing.
Four wires (circuits) are used on each O2 sensor: a
12±volt feed circuit for the sensor heating element; a
ground circuit for the heater element; a low-noise
sensor return circuit to the PCM, and an input cir-
cuit from the sensor back to the PCM to detect sen-
sor operation.
Oxygen Sensor Heaters/Heater Relays:
Depending on the emissions package, the heating ele-
ments within the sensors will be supplied voltage
from either the ASD relay, or 2 separate oxygen sen-
sor relays. Refer to Wiring Diagrams to determine
which relays are used.
The O2 sensor uses a Positive Thermal Co-efficient
(PTC) heater element. As temperature increases,
resistance increases. At ambient temperatures
around 70ÉF, the resistance of the heating element is
approximately 4.5 ohms on 4.0L engines. It is
approximately 13.5 ohms on the 4.7L engine. As the
sensor's temperature increases, resistance in the
heater element increases. This allows the heater to
maintain the optimum operating temperature of
approximately 930É-1100ÉF (500É-600É C). Although
the sensors operate the same, there are physical dif-
ferences, due to the environment that they operate
in, that keep them from being interchangeable.
Maintaining correct sensor temperature at all
times allows the system to enter into closed loop
operation sooner. Also, it allows the system to remain
in closed loop operation during periods of extended
idle.
14 - 50 FUEL INJECTIONWJ
O2S HEATER RELAY (Continued)

DIAGNOSIS AND TESTING - PUMP LEAKAGE
(1) Possible areas of pump leakage (Fig. 3).
STANDARD PROCEDURE
STANDARD PROCEDURE - INITIAL OPERATION
- 4.0L
WARNING: THE FLUID LEVEL SHOULD BE
CHECKED WITH ENGINE OFF TO PREVENT INJURY
FROM MOVING COMPONENTS.
CAUTION: Use MOPAR Power Steering Fluid or
equivalent. Do not use automatic transmission fluid
and do not overfill.
Wipe filler cap clean, then check the fluid level.
The dipstick should indicateCOLDwhen the fluid is
at normal ambient temperature.
(1) Fill the pump fluid reservoir to the proper level
and let the fluid settle for at least two minutes.
(2) Start the engine and let run for a few seconds
then turn engine off.
(3) Add fluid if necessary. Repeat the above proce-
dure until the fluid level remains constant after run-
ning the engine.
(4) Raise the front wheels off the ground.
(5) Slowly turn the steering wheel right and left,
lightly contacting the wheel stops at least 20 times.(6) Check the fluid level add if necessary.
(7) Lower the vehicle, start the engine and turn
the steering wheel slowly from lock to lock.
(8) Stop the engine and check the fluid level and
refill as required.
(9) If the fluid is extremely foamy or milky look-
ing, allow the vehicle to stand a few minutes and
repeat the procedure.
CAUTION: Do not run a vehicle with foamy fluid for
an extended period. This may cause pump damage.
STANDARD PROCEDURE - INITIAL OPERATION
- 4.7L
WARNING: THE FLUID LEVEL SHOULD BE
CHECKED WITH ENGINE OFF TO PREVENT INJURY
FROM MOVING COMPONENTS.
NOTE: Remove as much of the old fluid out of the
system as possible with a suction tool or by remov-
ing a hose, When a component has failed. Then
refill it with fresh fluid until it is clean. This may
have to be done more than once.
CAUTION: Use MOPAR Power Steering Fluid or
equivalent. Do not use automatic transmission fluid
and do not overfill.
Wipe filler cap clean, then check the fluid level.
The dipstick should indicateCOLDwhen the fluid is
at normal ambient temperature.
(1) Fill the pump fluid reservoir to the proper level
and let the fluid settle for at least two minutes.
(2) Start the engine and let run for a few seconds
then turn engine off.
(3) Add fluid if necessary. Repeat the above proce-
dure until the fluid level remains constant after run-
ning the engine.
(4) Raise the front wheels off the ground.
(5) Slowly turn the steering wheel right and left,
lightly contacting the wheel stops at least 20 times.
(6) Check the fluid level add if necessary.
(7) Lower the vehicle, start the engine, and use
the DRB III to activate the hydraulic fan on full fan
operation.
(8)
Turn the steering wheel slowly from lock to lock.
(9) Stop the engine, check the fluid level and refill
as required and repeat the process
CAUTION: Do not run a vehicle with foamy fluid for
an extended period. This may cause pump damage.
(10) If the fluid is extremely foamy or milky look-
ing, allow the vehicle to stand a few minutes and
repeat the procedure.
Fig. 3 4.0L Power Steering Pump
WJPUMP 19 - 33
PUMP (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
CLUNK NOISE FROM
DRIVELINE ON
CLOSED THROTTLE
4-3 DOWNSHIFT1. Transmission Fluid Low. 1. Add Fluid.
2. Throttle Cable Mis-adjusted. 2. Adjust cable.
3. Overdrive Clutch Select Spacer
Wrong Spacer.3. Replace overdrive piston thrust plate spacer.
3-4 UPSHIFT
OCCURS
IMMEDIATELY AFTER
2-3 SHIFT1. Overdrive Solenoid Connector or
Wiring Shorted.1.
Test connector and wiring for loose connections,
shorts or ground and repair as needed.
2. TPS Malfunction. 2. Test TPS and replace as necessary. Check with
DRBTscan tool.
3. PCM Malfunction. 3. Test PCM with DRBTscan tool and replace
controller if faulty.
4. Overdrive Solenoid Malfunction. 4. Replace solenoid.
5. Valve Body Malfunction. 5. Remove, disassemble, clean and inspect valve
body components. Make sure all valves and plugs
slide freely in bores. Polish valves with crocus
cloth if needed.
WHINE/NOISE
RELATED TO ENGINE
SPEED1. Fluid Level Low. 1. Add fluid and check for leaks.
2. Shift Cable Incorrect Routing. 2. Check shift cable for correct routing. Should not
touch engine or bell housing.
NO 3-4 UPSHIFT 1. O/D Switch In OFF Position. 1. Turn control switch to ON position.
2. Overdrive Circuit Fuse Blown. 2. Replace fuse. Determine why fuse failed and
repair as necessary (i.e., shorts or grounds in
circuit).
3. O/D Switch Wire Shorted/Open
Cut.3. Check wires/connections with 12V test lamp
and voltmeter. Repair damaged or loose
wire/connection as necessary.
4. Distance or Coolant Sensor
Malfunction.4. Check with DRBTscan tool and repair or
replace as necessary.
5. TPS Malfunction. 5. Check with DRBTscan tool and replace if
necessary.
6. Neutral Sense to PCM Wire
Shorted/Cut.6. Test switch/sensor as described in service
section and replace if necessary. Engine no start.
7. PCM Malfunction. 7. Check with DRBTscan tool and replace if
necessary.
8. Overdrive Solenoid Shorted/
Open.8. Replace solenoid if shorted or open and repair
loose or damaged wires (DRBTscan tool).
9. Solenoid Feed Orifice in Valve
Body Blocked.9. Remove, disassemble, and clean valve body
thoroughly. Check feed orifice.
10. Overdrive Clutch Failed. 10. Disassemble overdrive and repair as needed.
11. Hydraulic Pressure Low. 11. Pressure test transmission to determine
cause.
12. Valve Body Valve Stuck. 12. Repair stuck 3-4 shift valve, 3-4 timing valve.
13. O/D Piston Incorrect Spacer. 13. Remove unit, check end play and install
correct spacer.
14. Overdrive Piston Seal Failure. 14. Replace both seals.
15. O/D Check Valve/Orifice Failed. 15. Check for free movement and secure
assembly (in piston retainer). Check ball bleed
orifice.
WJAUTOMATIC TRANSMISSION - 42RE 21 - 23
AUTOMATIC TRANSMISSION - 42RE (Continued)

Normal calibration will be performed when sump
temperature is above 50 degrees F, or in the absence
of sump temperature data, after the first 10 minutes
of vehicle operation. Calibration of the pressure
transducer offset occurs each time the output shaft
speed falls below 200 RPM. Calibration shall be
repeated each 3 seconds the output shaft speed is
below 200 RPM. A 0.5 second pulse of 95% duty cycle
is applied to the governor pressure solenoid valve
and the transducer output is read during this pulse.
Averaging of the transducer signal is necessary to
reject electrical noise.
Under cold conditions (below 50 degrees F sump),
the governor pressure solenoid valve response may
be too slow to guarantee 0 psi during the 0.5 second
calibration pulse. Calibration pulses are continued
during this period, however the transducer output
valves are discarded. Transducer offset must be read
at key-on, under conditions which promote a stable
reading. This value is retained and becomes the off-
set during the9cold9period of operation.
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to
normal transmission line pressure. The outlet side of
the valve leads to the valve body governor circuit.
The solenoid valve regulates line pressure to pro-
duce governor pressure. The average current sup-
plied to the solenoid controls governor pressure. One
amp current produces zero kPa/psi governor pres-
sure. Zero amps sets the maximum governor pres-
sure.
The powertrain control module (PCM) turns on the
trans control relay which supplies electrical power to
the solenoid valve. Operating voltage is 12 volts
(DC). The PCM controls the ground side of the sole-
noid using the governor pressure solenoid control cir-
cuit.
GOVERNOR PRESSURE SENSOR
The sensor output signal provides the necessary
feedback to the PCM. This feedback is needed to ade-
quately control governor pressure.
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate channels line pressure to the
solenoid valve through the governor body. It also
channels governor pressure from the solenoid valve
to the governor circuit. It is the solenoid valve that
develops the necessary governor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conven-
tional governor can delay shifts, resulting in higherthan normal shift speeds and harsh shifts. The elec-
tronically controlled low temperature governor pres-
sure curve is higher than normal to make the
transmission shift at normal speeds and sooner. The
PCM uses a temperature sensor in the transmission
oil sump to determine when low temperature gover-
nor pressure is needed.
NORMAL OPERATION
Normal operation is refined through the increased
computing power of the PCM and through access to
data on engine operating conditions provided by the
PCM that were not available with the previous
stand-alone electronic module. This facilitated the
development of a load adaptive shift strategy - the
ability to alter the shift schedule in response to vehi-
cle load condition. One manifestation of this capabil-
ity is grade9hunting9prevention - the ability of the
transmission logic to delay an upshift on a grade if
the engine does not have sufficient power to main-
tain speed in the higher gear. The 3-2 downshift and
the potential for hunting between gears occurs with a
heavily loaded vehicle or on steep grades. When
hunting occurs, it is very objectionable because shifts
are frequent and accompanied by large changes in
noise and acceleration.
WIDE OPEN THROTTLE OPERATION
In wide-open throttle (WOT) mode, adaptive mem-
ory in the PCM assures that up-shifts occur at the
preprogrammed optimum speed. WOT operation is
determined from the throttle position sensor, which
is also a part of the emission control system. The ini-
tial setting for the WOT upshift is below the opti-
mum engine speed. As WOT shifts are repeated, the
PCM learns the time required to complete the shifts
by comparing the engine speed when the shifts occur
to the optimum speed. After each shift, the PCM
adjusts the shift point until the optimum speed is
reached. The PCM also considers vehicle loading,
grade and engine performance changes due to high
altitude in determining when to make WOT shifts. It
does this by measuring vehicle and engine accelera-
tion and then factoring in the shift time.
TRANSFER CASE LOW RANGE OPERATION
On four-wheel drive vehicles operating in low
range, the engine can accelerate to its peak more
rapidly than in Normal range, resulting in delayed
shifts and undesirable engine9flare.9The low range
governor pressure curve is also higher than normal
to initiate upshifts sooner. The PCM compares elec-
tronic vehicle speed signal used by the speedometer
to the transmission output shaft speed signal to
determine when the transfer case is in low range.
21 - 66 AUTOMATIC TRANSMISSION - 42REWJ
ELECTRONIC GOVERNOR (Continued)

(1) A result of restricted fluid flow through the
main and/or auxiliary cooler. This condition is usu-
ally the result of a faulty or improperly installed
drainback valve, a damaged main cooler, or severe
restrictions in the coolers and lines caused by debris
or kinked lines.
(2) Heavy duty operation with a vehicle not prop-
erly equipped for this type of operation. Trailer tow-
ing or similar high load operation will overheat the
transmission fluid if the vehicle is improperly
equipped. Such vehicles should have an auxiliary
transmission fluid cooler, a heavy duty cooling sys-
tem, and the engine/axle ratio combination needed to
handle heavy loads.
DIAGNOSIS AND TESTING - FLUID
CONTAMINATION
Transmission fluid contamination is generally a
result of:
²adding incorrect fluid
²failure to clean dipstick and fill tube when
checking level
²engine coolant entering the fluid
²internal failure that generates debris
²overheat that generates sludge (fluid break-
down)
²failure to reverse flush cooler and lines after
repair
²failure to replace contaminated converter after
repair
The use of non-recommended fluids can result in
transmission failure. The usual results are erratic
shifts, slippage, abnormal wear and eventual failure
due to fluid breakdown and sludge formation. Avoid
this condition by using recommended fluids only.
The dipstick cap and fill tube should be wiped
clean before checking fluid level. Dirt, grease and
other foreign material on the cap and tube could fall
into the tube if not removed beforehand. Take the
time to wipe the cap and tube clean before withdraw-
ing the dipstick.
Engine coolant in the transmission fluid is gener-
ally caused by a cooler malfunction. The only remedy
is to replace the radiator as the cooler in the radiator
is not a serviceable part. If coolant has circulated
through the transmission, an overhaul is necessary.
The transmission cooler and lines should be
reverse flushed whenever a malfunction generates
sludge and/or debris. The torque converter should
also be replaced at the same time.
Failure to flush the cooler and lines will result in
recontamination. Flushing applies to auxiliary coolers
as well. The torque converter should also be replaced
whenever a failure generates sludge and debris. This
is necessary because normal converter flushing proce-
dures will not remove all contaminants.
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUID LEVEL
CHECK
Low fluid level can cause a variety of conditions
because it allows the pump to take in air along with
the fluid. As in any hydraulic system, air bubbles
make the fluid spongy, therefore, pressures will be
low and build up slowly.
Improper filling can also raise the fluid level too
high. When the transmssion has too much fluid, the
geartrain churns up foam and cause the same condi-
tions which occur with a low fluid level.
In either case, air bubbles can cause overheating
and/or fluid oxidation, and varnishing. This can
interfere with normal valve, clutch, and accumulator
operation. Foaming can also result in fluid escaping
from the transmission vent where it may be mis-
taken for a leak.
After the fluid has been checked, seat the dipstick
fully to seal out water and dirt.
The transmission has a dipstick to check oil level.
It is located on the right side of the engine. Be sure
to wipe all dirt from dipstick handle before removing.
Fluid level is checked with the engine running at
curb idle speed, the transmission in NEUTRAL and
the transmission fluid at normal operating tempera-
ture.The engine should be running at idle
speed for at least one minute, with the vehicle
on level ground.
The transmission fluid level can be checked two
ways.
PROCEDURE ONE
(1) Transmission fluid must be at normal operat-
ing temperature for accurate fluid level check. Drive
vehicle if necessary to bring fluid temperature up to
normal hot operating temperature of 82ÉC (180ÉF).
(2) Position vehicle on level surface.
(3) Start and run engine at curb idle speed.
(4) Apply parking brakes.
(5) Shift transmission momentarily into all gear
ranges. Then shift transmission back to NEUTRAL.
(6) Clean top of filler tube and dipstick to keep
dirt from entering tube.
(7) Remove dipstick (Fig. 87) and check fluid level
as follows:
(a) Correct acceptable level is in crosshatch area.
(b) Correct maximum level is to MAX arrow
mark.
(c) Incorrect level is at or below MIN line.
(d) If fluid is low, add only enough MopartAT F
+4, type 9602, to restore correct level. Do not over-
fill.
21 - 70 AUTOMATIC TRANSMISSION - 42REWJ
FLUID AND FILTER (Continued)

STANDARD PROCEDURE
STANDARD PROCEDURE - FLUID LEVEL
CHECK
Low fluid level can cause a variety of conditions
because it allows the pump to take in air along with
the fluid. As in any hydraulic system, air bubbles
make the fluid spongy, therefore, pressures will be
low and build up slowly.
Improper filling can also raise the fluid level too
high. When the transmssion has too much fluid, the
geartrain churns up foam and cause the same condi-
tions which occur with a low fluid level.
In either case, air bubbles can cause overheating
and/or fluid oxidation, and varnishing. This can inter-
fere with normal valve, clutch, and accumulator opera-
tion. Foaming can also result in fluid escaping from the
transmission vent where it may be mistaken for a leak.
After the fluid has been checked, seat the dipstick
fully to seal out water and dirt.
The transmission has a dipstick to check oil level.
It is located on the right side of the engine. Be sure
to wipe all dirt from dipstick handle before removing.
The torque converter fills in both the P (PARK)
and N (NEUTRAL) positions. Place the selector lever
in P (PARK) to be sure that the fluid level check is
accurate.The engine should be running at idle
speed for at least one minute, with the vehicle
on level ground.At normal operating temperature(approximately 82 C. or 180 F.), the fluid level is cor-
rect if it is in the HOT region (cross-hatched area) on
the oil level indicator. The fluid level will be approx-
imately at the upper COLD hole of the dipstick at
70É F fluid temperature.
NOTE: Engine and Transmission should be at nor-
mal operating temperature before performing this
procedure.
(1) Start engine and apply parking brake.
(2) Shift the transmission into DRIVE for approxi-
mately 2 seconds.
(3) Shift the transmission into REVERSE for
approximately 2 seconds.
(4) Shift the transmission into PARK.
(5)
Hook up DRBtscan tool and select transmission.
(6) Select sensors.
(7) Read the transmission temperature value.
(8) Compare the fluid temperature value with the
chart. (Fig. 59)
(9) Adjust transmission fluid level shown on the
dipstick according to the chart.
NOTE: After adding any fluid to the transmission,
wait a minimum of 2 minutes for the oil to fully
drain from the fill tube into the transmission before
rechecking the fluid level.
(10) Check transmission for leaks.
Fig. 59 Transmission Fluid Temperature Chart
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 229
FLUID AND FILTER (Continued)

gap should be between 0.35 to 0.65 millimeter (0.014
to 0.026 inch). If the proper air gap is not obtained,
add or subtract shims as needed until the desired air
gap is obtained.
(9) Install the compressor shaft bolt. Tighten the
bolt to 13 N´m (115 in. lbs.).
NOTE: The shims may compress after tightening
the shaft bolt. Check the air gap in four or more
places to verify the air gap is still correct. Spin the
pulley before performing a final check of the air
gap.
(10) To complete the installation, (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/A/C
COMPRESSOR - INSTALLATION)
A/C COMPRESSOR CLUTCH
RELAY
DESCRIPTION
The compressor clutch relay is a International
Standards Organization (ISO) micro-relay. The termi-
nal designations and functions are the same as a con-
ventional ISO relay. However, the micro-relay
terminal orientation (footprint) is different, the cur-
rent capacity is lower, and the relay case dimensions
are smaller than those of the conventional ISO relay.
OPERATION
The compressor clutch relay is a electromechanical
device that switches battery current to the compres-
sor clutch coil when the Powertrain Control Module
(PCM) grounds the coil side of the relay. The PCM
responds to inputs from the a/c compressor switch on
the a/c heater control panel, the Automatic Zone Con-
trol (AZC) control module (if the vehicle is so
equipped), the a/c fin probe, and the a/c high pres-
sure transducer. (Refer to 24 - HEATING & AIR
CONDITIONING/CONTROLS/A/C COMPRESSOR
CLUTCH RELAY - DIAGNOSIS AND TESTING)
The compressor clutch relay is located in the Power
Distribution Center (PDC) in the engine compart-
ment. Refer to the PDC label for relay identification
and location.
The compressor clutch relay cannot be repaired
and, if faulty or damaged, it must be replaced.
DIAGNOSIS AND TESTING - A/C COMPRESSOR
CLUTCH RELAY
For circuit descriptions and diagrams, refer to the
appropriate wiring information.
The compressor clutch relay (Fig. 10) is located in
the Power Distribution Center (PDC). Refer to the
PDC label for relay identification and location.Remove the relay from the PDC to perform the fol-
lowing tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   5 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, see the Relay Circuit Test procedure
in this group. If not OK, replace the faulty relay.
RELAY CIRCUIT TEST
For circuit descriptions and diagrams, refer to the
appropriate wiring information..
(1) The relay common feed terminal cavity (30) is
connected to fused battery feed. There should be bat-
tery voltage at the cavity for relay terminal 30 at all
times. If OK, go to Step 2. If not OK, repair the open
circuit to the fuse in the PDC as required.
(2) The relay normally closed terminal (87A) is not
used in this application. Go to Step 3.
(3) The relay normally open terminal cavity (87) is
connected to the compressor clutch coil. There should
be continuity between this cavity and the A/C com-
pressor clutch relay output circuit cavity of the com-
pressor clutch coil wire harness connector. If OK, go
to Step 4. If not OK, repair the open circuit as
required.
(4) The relay coil battery terminal (86) is con-
nected to the fused ignition switch output (run/start)
circuit. There should be battery voltage at the cavity
for relay terminal 86 with the ignition switch in the
On position. If OK, go to Step 5. If not OK, repair the
Fig. 10 A/C COMPRESSOR CLUTCH RELAY
30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED
24 - 16 CONTROLSWJ
A/C COMPRESSOR CLUTCH (Continued)

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)