
3.2.2 CAN BUS
The CAN bus (controller area network) is a data
bus system specifically design for inter module
communication on this vehicle. The CAN bus con-
sists of a special twisted two-core cable. Control
modules are connected to this9twisted pair9. The
CAN bus incorporates two terminating resistors.
One terminator is built into the Engine Control
Module (ECM) and the other is built into the Sentry
Key Remote Entry Module (SKREEM). Each resis-
tor has a value of 120 ohms. The resistor condition
can be confirmed by disconnecting the control mod-
ule and measuring the resistance value at the
appropriate control module pins. This measure-
ment should read 120 ohms. The two CAN circuits,
CAN C Bus (+) and CAN C Bus (-), are bridged by
these two terminating resistors when all control
modules are connected to the bus. These two resis-
tors are connected to the CAN bus network in
parallel. The measurement between the two
twisted CAN circuits, with both the ECM and
SKREEM connected, should measure a value of 60
ohms.
The CAN bus is bi-directional. This means that
each connected control module can send and receive
information. Transmission of data takes place re-
dundantly via both circuits. The data bus levels are
mirrored, meaning that if the binary level on one
circuit is 0, the other circuit transmits binary level
1 and vice versa. The two line concept is used for
two reasons: for fault identification and as a safety
concept.
If a voltage peak occurs on just one circuit, the
receivers can identify this as a fault and ignore the
voltage peak. If a short circuit or interruption
occurs on one of the two CAN circuits, a software-
hardware linked safety concept allows switching to
a single-line operation. The defective CAN circuit is
shut down. A specific data protocol controls how and
when the participants can send and receive.
NOTE: It is important to note the CAN Bus
circuits are used for inter-module
communication only, and is no way
connected to the K-Lines.
The following modules that use the CAN Bus on
this vehicle are:
²Automatic Temperature Control (ATC)
²Controller Antilock Brake (CAB)
²Engine Control Module (ECM)
²Instrument Cluster (IC)
²Sentry Key Remote Entry Module (SKREEM)
²Shifter Assembly (SA)
²Transmission Control Module (TCM)
3.3 HEATING & A/C SYSTEM
3.3.1 AUTOMATIC TEMPERATURE
CONTROL (ATC)
3.3.1.1 SYSTEM CONTROLS
The ATC Module:
²is fully addressable with the DRBIIIt.
IThe DRBIIItcommunicates with the ATC
Module through the Diagnostic Link Connector
(DLC) via a K-Line.
²communicates with other modules over the Con-
troller Area Network (CAN) C Bus.
²controls A/C clutch operation.
²controls EBL operation.
²controls water cycle valve operation.
IThe water cycle valve is a normally open valve,
meaning that it allows full engine coolant flow
through the heater core when no power is
delivered to the valve. The ATC controls the
valve with a pulse width signal. The lower the
percentage of the pulse width signal the more
the valve is open.
²controls Residual Heat Utilization (REST) func-
tion.
²controls blower motor operation, providing four
blower speeds (Low, M1, M2, & High).
²controls recirculation air solenoid valve.
²controls the mode door via cables.
²controls the main power supply to the Heater
Booster (if equipped).
²uses air inlet temperature sensor, air outlet tem-
perature sensor, and evaporator temperature
sensor input, as well as data from other modules
to maintain occupant comfort levels.
3.3.1.2 SYSTEM DIAGNOSTICS
Fault detection is through active and stored Diag-
nostic Trouble Codes (DTCs)
²DTCs are displayed by the DRBIIIt.
²Active DTCs are those which currently exist in
the system. The condition causing the fault must
be repaired in order to clear this type of DTC.
²Stored DTCs are those which occurred in the
system since the ATC Module received the last
9clear diagnostic info9message.
Testing Preparation & Diagnostics
Set the necessary system functions accordingly so
that all of the following prerequisites are met prior
to performing diagnostic tests on the ATC system:
5
GENERAL INFORMATION

1. Connect the DRBIIItto the DLC.
2. Place the shift lever in park.
3. Start the engine.
4. Set the blower to high speed.
5. Set the temperature selector to full cold.
6. Press air conditioning switch on.
7. With the DRBIIItin Sensors, verify that the:
A. ambient temperature is above 59F (15C).
B. refrigerant pressure is between 29 and 348
PSI (2 and 24 bar).
C. evaporator temperature is above 36.5F
(2.5C).
D. coolant temperature is above 158F (70C).
When all of the prerequisites have been met, use
the DRBIIItto record and erase all stored ATC
DTCs, and then select System Tests, and run the
ATC Function Test. When complete, check to see if
any active DTCs are present. If so, refer to the
symptom list in the Heating & A/C category for the
diagnostic procedure(s). If there are no DTCs
present, yet the performance seems less than ideal,
use the DRBIIItto look at all sensor values and the
status of the various inputs and outputs to see if
there is a deficiency detected that has not fully shut
down the system. For additional information, refer
to Sensor Values and Input/Output Status under
Diagnostic Tips in this section and to Section 11.0
for evaporator temperature sensor and air outlet
temperature sensor resistance to temperature spec-
ifications charts. Also, confirm that the water cycle
valve is functioning. Remember that the valve is
normally open. The pulse width signal will offer
insight into the valve's operation. The lower the
percentage number, the more open the valve be-
comes. Confirm that the valve is responding to the
signal from the ATC. If functioning correctly, verify
mode and blend door operation. If okay, the diagno-
sis then becomes purely refrigerant system related.
Attach the appropriate gauges and diagnose the
refrigeration system. Refer to the Service Informa-
tion for refrigerant system diagnostic procedures.
DIAGNOSTIC TIPS
SENSOR VALUES
Ambient Air Temperature
The Instrument Cluster transmits Ambient Air
Temperature Sensor data. In the event of a CAN
Bus communication failure, the last stored value is
displayed as a substitute value.
Interior Temperature
The normal range for the Interior Temperature
Sensor is from 32ÉF to 104ÉF. An implausible tem-
perature value indicates that the Interior Temper-
ature Sensor is bad. The repair in this case would be
to replace the ATC Module since the sensor is
integral to the module.Evaporator Temperature
The normal range for the Evaporator Temperature
Sensor is from 14ÉF to 104ÉF. A substitute value of
14ÉF with no updates indicates an Evaporator Tem-
perature Sensor circuit failure.
Air Outlet Temperature
The normal range for the Air Outlet Temperature
Sensor is from 32ÉF to 203ÉF. A substitute value of
111.1ÉF indicates an Air Outlet Temperature Sensor
circuit failure.
Coolant Temperature
The Engine Control Module transmits Coolant
Temperature Sensor date. In the event of a CAN
Bus communication failure, 257ÉF is displayed as a
substitute value.
Interior Temperature Controller
The normal range for the Blend control is from 62ÉF
to 144ÉF. This value represents the temperature set
by the operator. An implausible temperature value
or a temperature value that fails to change when
rotating the Blend control indicates that the Blend
control is bad. The repair in this case would be to
replace the ATC Module since the Blend control
integral to the module.
Refrigerant Pressure
The normal range for the Refrigerant Pressure
Sensor is from 29 PSI to 406 PSI. A substitute value
of 413 PSI indicates a Refrigerant Pressure Sensor
circuit failure. In addition, the normal range for
Pressure Sensor voltage is 0 volts to 5 volts. A value
of 0.9 volts indicates an open voltage supply circuit,
while a value of -999 indicates an open in all three
sensor circuits.
Water Cycle Valve
The normal range of the Water Cycle Valve is from
0% to 100%. The value indicates the extent to which
the valve is closed. A value of 100% indicates that
the valve is fully closed.
Intense Inst Light
The Instrument Cluster transmits this data. The
normal range for lighting intensity is from 0% to
100%. The value indicates the extent to which the
illumination has dimmed. A value of 0% indicates
bright while a value >0% indicates dimming. In the
event of a CAN Bus communication failure, 0% is
displayed as a substitute value.
INPUT/OUTPUT STATUS
Compressor Clutch
The ATC Module transmits this data. A status of
9ON9indicates that the compressor is operational. A
status of9OFF9indicates the compressor is not
operational.
6
GENERAL INFORMATION

Symptom:
A/C COMPRESSOR CONTROL HIGH OR OPEN (ACTIVE)
POSSIBLE CAUSES
A/C COMPRESSOR CLUTCH CONTROL CIRCUIT SHORTED TO VOLTAGE
A/C COMPRESSOR CLUTCH
A/C COMPRESSOR CLUTCH CONTROL CIRCUIT OPEN
AUTOMATIC TEMPERATURE CONTROL (ATC)
TEST ACTION APPLICABILITY
1 Turn the ignition off.
NOTE: Check connectors - Clean/repair as necessary.
Disconnect the A/C Compressor Clutch harness connector.
Turn the ignition on.
Press the Air Conditioning switch off.
Measure the voltage of the A/C Compressor Clutch Control circuit.
Is the voltage above 10.0 volts?All
Ye s!Go To 2
No!Go To 4
2 Turn the ignition off.
NOTE: Check connectors - Clean/repair as necessary.
Disconnect the Automatic Temperature Control (ATC) C1 harness connector.
Disconnect the A/C Compressor Clutch harness connector.
Turn the ignition on.
Measure the voltage of the A/C Compressor Clutch Control circuit.
Is the voltage above 0.2 volts?All
Ye s!Repair the A/C Compressor Clutch Control circuit for a short to
voltage.
Perform BODY VERIFICATION TEST - VER 1.
No!Go To 3
3 Turn the ignition off.
NOTE: Check connectors - Clean/repair as necessary.
Reconnect the Automatic Temperature Control (ATC) C1 harness connector.
Reconnect the A/C Compressor Clutch harness connector.
Verify that the A/C Compressor Clutch Ground is clean and tight.
Turn the ignition on.
With the DRBIIIt, erase DTCs.
Turn the ignition off, wait 5 seconds, then turn the ignition on.
With the DRBIIIt, read Automatic Temperature Control DTCs.
Does the DRBIIItdisplay: A/C COMPRESSOR CONTROL HIGH OR OPEN?All
Ye s!Replace the A/C Compressor Clutch in accordance with the
Service Information.
Perform BODY VERIFICATION TEST - VER 1.
No!Test Complete.
128
HEATING & A/C

TEST ACTION APPLICABILITY
4 Turn the ignition off.
NOTE: Check connectors - Clean/repair as necessary.
Disconnect the Automatic Temperature Control (ATC) C1 harness connector.
Disconnect the A/C Compressor Clutch harness connector.
Measure the resistance of the A/C Compressor Clutch Control circuit between the
Automatic Temperature Control (ATC) C1 harness connector and the A/C Compres-
sor Clutch harness connector.
Is the resistance below 5.0 ohms?All
Ye s!Replace the Automatic Temperature Control (ATC) in accordance
with the Service Information.
Perform BODY VERIFICATION TEST - VER 1.
No!Repair the A/C Compressor Clutch Control circuit for an open.
Perform BODY VERIFICATION TEST - VER 1.
129
HEATING & A/C
A/C COMPRESSOR CONTROL HIGH OR OPEN (ACTIVE) ÐContinued

Symptom:
A/C COMPRESSOR CONTROL SHORTED LOW (ACTIVE)
POSSIBLE CAUSES
A/C COMPRESSOR CLUTCH
A/C COMPRESSOR CLUTCH CONTROL CIRCUIT SHORTED TO GROUND
A/C COMPRESSOR CLUTCH CONTROL CIRCUIT SHORTED TO GROUND CIRCUIT
A/C COMPRESSOR CLUTCH CONTROL CIRCUIT SHORTED TO SENSOR GROUND CIRCUIT
AUTOMATIC TEMPERATURE CONTROL (ATC)
TEST ACTION APPLICABILITY
1 Turn the ignition on.
Press the Air Conditioning switch off.
Turn the ignition off.
Disconnect the A/C Compressor Clutch harness connector.
Turn the ignition on.
With the DRBIIIt, record and erase Automatic Temperature Control DTCs.
Turn the ignition off, wait 5 seconds, then turn the ignition on.
With the DRBIIIt, read the Automatic Temperature Control DTCs.
Does the DRBIIItdisplay: A/C COMPRESSOR CONTROL HIGH OR OPEN?All
Ye s!Replace the A/C Compressor Clutch in accordance with the
Service Information.
Perform BODY VERIFICATION TEST - VER 1.
No!Go To 2
2 Turn the ignition off.
Disconnect the A/C Compressor Clutch harness connector.
Disconnect the Automatic Temperature Control (ATC) C1 harness connector.
Measure the resistance between ground and the A/C Compressor Clutch Control
circuit.
Is the resistance below 10k ohms?All
Ye s!Repair the A/C Compressor Clutch Control circuit for a short to
ground.
Perform BODY VERIFICATION TEST - VER 1.
No!Go To 3
3 Turn the ignition off.
Disconnect the A/C Compressor Clutch harness connector.
Disconnect the Automatic Temperature Control (ATC) C1 harness connector.
Measure the resistance between the A/C Compressor Clutch Control circuit and the
Ground circuit in the Automatic Temperature Control C1 harness connector.
Is the resistance below 10k ohms?All
Ye s!Repair the A/C Compressor Clutch Control circuit for a short to
the Ground circuit.
Perform BODY VERIFICATION TEST - VER 1.
No!Go To 4
132
HEATING & A/C

TEST ACTION APPLICABILITY
4 Turn the ignition off.
Disconnect the A/C Compressor Clutch harness connector.
Disconnect the Automatic Temperature Control (ATC) C1 harness connector.
Measure the resistance between the A/C Compressor Clutch Control circuit and the
Sensor Ground circuit in the Automatic Temperature Control C1 harness connector.
Is the resistance below 10k ohms?All
Ye s!Repair the A/C Compressor Clutch Control circuit for a short to
the Sensor Ground circuit.
Perform BODY VERIFICATION TEST - VER 1.
No!Replace the Automatic Temperature Control (ATC) in accordance
with the Service Information.
Perform BODY VERIFICATION TEST - VER 1.
133
HEATING & A/C
A/C COMPRESSOR CONTROL SHORTED LOW (ACTIVE) ÐContinued

AUTOMATIC TEMPERATURE CONTROL MODULE C1 - BROWNCAV CIRCUIT FUNCTION
1 16RD/BL FUSED B(+)
2 18DG/RD (REST SYSTEM) CIRCULATION PUMP CONTROL
3 18BK/RD A/C AUXILIARY FAN RELAY HIGH SIDE CONTROL
4 16BL/YL HEATER BOOSTER MODE
5 18BR/VT WATER CYCLE VALVE CONTROL
6 20RD/BL 5 VOLT SUPPLY
7 18BK/YL K-IC/ATC/HBM/CHM
8 16RD/YL/WT FUSED D(+) RELAY OUTPUT
8 20BL/VT D(+) RELAY CONTROL
9 16GY/DG/RD LAMP DRIVER
10 16BL CABIN HEATER CONTROL
11 16BK/BL/WT RECIRCULATED AIR SOLENOID VALVE CONTROL
12 16BL/DG A/C COMPRESSOR CLUTCH CONTROL
13 18BR/DG EVAPORATOR TEMPERATURE SENSOR SIGNAL
14 - -
15 16BR GROUND
16 18BR/GY AIR OUTLET TEMPERATURE SENSOR SIGNAL
17 20DG/WT CAN C BUS (+)
18 18BR/BL SENSOR GROUND
19 20BR/RD REFRIGERANT PRESSURE SENSOR FEEDBACK
20 20DG CAN C BUS (-)
21 16BK/BL/DG FUSED IGNITION SWITCH OUTPUT
AUTOMATIC TEMPERATURE CONTROL MODULE C2CAV CIRCUIT FUNCTION
1 14BK/VT FAN STAGE 1 RELAY OUTPUT
1 12YL BLOWER MOTOR LOW DRIVER
2 12WT BLOWER MOTOR HIGH DRIVER
3 12WT/BK BLOWER MOTOR M1 DRIVER
4 12YL/BK BLOWER MOTOR M2 DRIVER
5 12RD/BL FUSED B(+)
AUXILIARY HEATER CONTROLCAV CIRCUIT FUNCTION
1 16GY/DG/RD LAMP DRIVER
2- -
3 16RD/YL FUSED B(+)
4- -
5- -
6- -
7 16YL CABIN HEATER CONTROL
8- -
9- -
10 16BR GROUND
BLOWER MOTOR RESISTOR BLOCKCAV CIRCUIT FUNCTION
1 12YL/BK BLOWER MOTOR M2 DRIVER
2 12YL BLOWER MOTOR LOW DRIVER
3 12WT/BK BLOWER MOTOR M1 DRIVER
4 12DG BLOWER MOTOR HIGH DRIVER
C
O
N
N
E
C
T
O
R
P
I
N
O
U
T
S
259
CONNECTOR PINOUTS

TABLE OF CONTENTS - Continued
P2500-FUEL PRESSURE SOLENOID CIRCUIT OPEN CIRCUIT................173
P2501-FUEL PRESSURE SOLENOID CIRCUIT SHORTED TO GROUND OR B+ . .173
P2197-FUEL QUANTITY SOLENOID OPEN CIRCUIT.........................177
P2198-FUEL QUANTITY SOLENOID SHORT TO VOLTAGE...................177
P2199-FUEL QUANTITY SOLENOID SHORT TO GROUND....................177
P2502-FUEL QUANTITY SOLENOID SHORT TO GROUND....................177
P2203-TORQUE REDUCTION MESSAGE FROM ABS - CAN PLAUSIBILITY.....180
P2203-TORQUE REDUCTION MESSAGE FROM ABS - MESSAGE ERROR......180
P2203-TORQUE REDUCTION MESSAGE FROM ABS - MESSAGES MISSING . . .180
P2203-TORQUE REDUCTION MESSAGE FROM ABS - NO COMMUNIOCATION .180
P2203-TORQUE REDUCTION MESSAGE FROM ABS - PLAUSIBILITY #1.......180
P2203-TORQUE REDUCTION MESSAGE FROM ABS PLAUSIBILITY #2.........180
P2208-ABS BRAKE SIGNAL CAN MESSAGE IMPLAUSIBLE..................180
P2208-ABS CAN BRAKE SIGNAL PLAUSIBILITY............................180
P2209-ABS CAN MESSAGE MISSING OR INCORRECT......................180
P2253-STEERING ANGLE SENSOR PLAUSIBILITY..........................180
P2204-TORQUE REDUCTION MESSAGE FROM TCM - CAN PLAUSIBILITY.....182
P2204-TORQUE REDUCTION MESSAGE FROM TCM - ENGINE STOP.........182
P2204-TORQUE REDUCTION MESSAGE FROM TCM - MESSAGE ERROR.....182
P2204-TORQUE REDUCTION MESSAGE FROM TCM - MESSAGES MISSING . . .182
P2204-TORQUE REDUCTION MESSAGE FROM TCM - PLAUSIBILITY..........182
P2204-TORQUE REDUCTION MESSAGE FROM TCM - TCM DTC #1...........182
P2204-TORQUE REDUCTION MESSAGE FROM TCM - TCM DTC #2...........182
P2210-ESM CAN MESSAGE MISSING OR INCORRECT......................184
P2234-ABS DTC EXTERNAL QUANTITY CONTROL FAULT PRESENT..........184
P2252-LATERAL ACCELERATOR SENSOR PLAUSIBILTY.....................184
P2211-ETC CAN MESSAGE MISSING OR INCORRECT......................186
P2258-TCM MESSAGE ERROR..........................................186
P2258-TCM NO CAN MESSAGE..........................................186
P2217-TCM DTC INTERNAL FAULT PRESENT..............................188
P2218-TCM DTC 1-2 AND 4-5 SHIFT SOLENOID FAULT PRESENT............188
P2219-TCM DTC 2-3 SHIFT SOLENOID FAULT PRESENT....................188
P2220-TCM DTC 3-4 SHIFT SOLENOID FAULT PRESENT....................188
P2221-TCM DTC TORQUE CONVERTER CLUTCH SOLENOID FAULT PRESENT .188
P2222-TCM DTC MODULATING PRESSURE SOLENOID FAULT PRESENT......188
P2223-TCM DTC SHIFT PRESSURE SOLENOID FAULT PRESENT.............188
P2224-TCM DTC VALVE VOLTAGE SUPPLY FAULT PRESENT................188
P2225-TCM DTC SPEED SENSOR VOLTAGE FAULT PRESENT...............188
P2226-TCM DTC EWM CAN MESSAGE FAULT PRESENT....................188
P2227-TCM DTC RIGHT REAR WHEEL SPEED IMPLAUSIBLE FAULT PRESENT .188
P2228-TCM DTC TRANSMISSION RATIO ERROR FAULT PRESENT...........188
P2229-TCM DTC CAN MSG IMPLAUSIBLE FAULT PRESENT.................188
P2230-TCM DTC TCC EXCESSIVE POWER CONSUMPTION FAULT PRESENT . .188
P2231-TCM DTC NOT UNEQUIVOCAL FAULT PRESENT.....................188
P2232-TCM DTC NEGATIVE GEAR COMPARISON FAULT PRESENT...........188
P2240-ABS STEERING ANGLE SENSOR CAN MESSAGE IMPLAUSIBLE 1......190
P2240-ABS STEERING ANGLE SENSOR CAN MESSAGE IMPLAUSIBLE 2......190
P2242-ABS BRAKE MESSAGE PLAUSIBILITY 1.............................192
P2242-ABS BRAKE MESSAGE PLAUSIBILITY 2.............................192
P2244-INSTRUMENT CLUSTER MESSAGE PLAUSIBILITY...................194
P2259-TORQUE REDUCTION MESSAGE FROM HVAC- PARITY ERROR........196
P2259-TORQUE REDUCTION MESSAGE FROM HVAC- SWITCH SIGNAL
ERROR..............................................................196
viii