Page 427 of 4284
TEST ACTION APPLICABILITY
5 If there are no possible causes remaining, view repair. All
Repair
Replace the Cabin Heater Assist in accordance with the service
information.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
398
COMMUNICATION
*NO RESPONSE FROM CABIN HEATER ASSIST - DIESEL ONLY Ð
Continued
Page 431 of 4284

Symptom:
*NO RESPONSE FROM ECM (SCI ONLY) - DIESEL ONLY
POSSIBLE CAUSES
CHECK ECM POWERS AND GROUNDS
CABIN HEATER ASSIST
SCI TRANSMIT CIRCUIT SHORTED TO VOLTAGE
SCI TRANSMIT CIRCUIT SHORTED TO GROUND
SCI TRANSMIT CIRCUIT OPEN
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1 Perform the symptom Checking ECM Power and Ground Circuits in the Driveability
category.
Did the vehicle pass this test?All
Ye s®Go To 2
No®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
2 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the DRB from the DLC.
Measure the resistance between ground and the SCI Transmit circuit.
Is the resistance below 5.0 ohms?All
Ye s®Go To 3
No®Go To 4
3 Turn the ignition off.
Disconnect the Cabin Heater Assist C1 harness connector.
Measure the resistance between ground and the SCI Transmit circuit.
Is the resistance below 5.0 ohms?All
Ye s®Repair the SCI Transmit circuit for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
No®Replace the Cabin Heater Assist in accordance with the service
information.
Perform ROAD TEST VERIFICATION - VER-2.
4 Turn the ignition off.
Disconnect the DRB from the DLC.
Disconnect the ECM harness connectors.
Disconnect the Cabin Heater Assist C1 harness connector.
Turn the ignition on.
Measure the voltage of the SCI Transmit circuit at the DLC connector (cav 7).
Is the voltage above 1.0 volt?All
Ye s®Repair the SCI Transmit circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 5
402
COMMUNICATION
Page 541 of 4284

Symptom List:
A/C FAULT (ACTIVE) - MANUAL A/C
CHECKSUM FAILURE (ACTIVE) - MANUAL A/C
POWER FAULT (ACTIVE) - MANUAL A/C
REAR DEFOG FAILURE (ACTIVE) - MAN A/C
RECIRCULATION FAULT (ACTIVE) - MANUAL A/C
UNKNOWN FAULT DETECTED (ACTIVE) - MANUAL A/C
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be A/C FAULT (ACTIVE) - MANUAL
A/C.
When Monitored and Set Condition:
A/C FAULT (ACTIVE) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the A/C switch stays closed for 10 minutes.
CHECKSUM FAILURE (ACTIVE) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the calibrated check sum does not match the stored
value.
POWER FAULT (ACTIVE) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Power switch stays closed for 10 minutes.
REAR DEFOG FAILURE (ACTIVE) - MAN A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Rear Window Defogger switch stays closed for 10
minutes.
RECIRCULATION FAULT (ACTIVE) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Recirc switch stays closed for 10 minutes.
UNKNOWN FAULT DETECTED (ACTIVE) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the A/C - Heater Cotrol Module detects an internal
fault.
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HEATING & A/C
Page 542 of 4284
POSSIBLE CAUSES
A/C - HEATER CONTROL MODULE
TEST ACTION APPLICABILITY
1 View repairAll
Repair
Replace the A/C - Heater Control Module in accordance with the
Service Information.
Perform BODY VERIFICATION TEST - VER 1.
513
HEATING & A/C
A/C FAULT (ACTIVE) - MANUAL A/C ÐContinued
Page 543 of 4284

Symptom List:
A/C FAULT (STORED) - MANUAL A/C
BACKLIGHT DIMMING RX FAILURE (STORED) - MANUAL A/C
BLEND OVERCURRENT (STORED) - MANUAL A/C
CHECKSUM FAILURE (STORED) - MANUAL A/C
EVAPORATOR TEMPERATURE SENSOR CIRCUIT OPEN
(STORED) - MANUAL A/C
EVAPORATOR TEMPERATURE SENSOR CIRCUIT SHORT
(STORED) - MANUAL A/C
LOOPBACK FAILURE (STORED) - MANUAL A/C
LOOPBACK TEST FAILURE (STORED) - MANUAL A/C
MODE OVERCURRENT (STORED) - MANUAL A/C
NO BCM MESSAGE RECEIVED (STORED) - MANUAL A/C
NO PCM MESSAGE RECEIVED (STORED) - MANUAL A/C
PCM COMMUNICATION FAILURE (STORED) - MANUAL A/C
POWER FAULT (STORED) - MANUAL A/C
REAR BLEND OVERCURRENT (STORED) - MANUAL A/C
REAR BLEND POT CIRCUIT OPEN (STORED) - MANUAL A/C
REAR BLEND POT CIRCUIT SHORT (STORED) - MANUAL A/C
REAR DEFOG FAILURE (STORED) - MANUAL A/C
REAR MODE OVERCURRENT (STORED) - MANUAL A/C
RECIRC OVERCURRENT (STORED) - MANUAL A/C
RECIRCULATION FAULT (STORED) - MANUAL A/C
TX FAILURE (STORED) - MANUAL A/C
UNKNOWN FAULT DETECTED (STORED) - MANUAL A/C
VEHICLE ODOMETER FAILURE (STORED) - MANUAL A/C
ZONE OVERCURRENT (STORED) - MANUAL A/C
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be A/C FAULT (STORED) - MANUAL
A/C.
When Monitored and Set Condition:
A/C FAULT (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the A/C switch stays closed for 10 minutes.
BACKLIGHT DIMMING RX FAILURE (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: If the A/C - Heater Control Module does not receive the dimming function
message from the BCM for more than 5 seconds, then the A/C - Heater Control Module
LEDs will default to full brightness and the DTC will set.
514
HEATING & A/C
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BLEND OVERCURRENT (STORED) - MANUAL A/C
When Monitored: When actuator movement is requested.
Set Condition: All (Blend, Mode, Recirc, and Zone) Overcurrent DTCs will set if the A/C
- Heater Control Module detects an excessive current draw on the Common Door Drive
circuit(s).
CHECKSUM FAILURE (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the calibrated check sum does not match the stored
value.
EVAPORATOR TEMPERATURE SENSOR CIRCUIT OPEN (STORED) - MANUAL
A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Evaporator Temperature Sensor/sensor circuit is
open.
EVAPORATOR TEMPERATURE SENSOR CIRCUIT SHORT (STORED) - MAN-
UAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Evaporator Temperature Sensor/sensor circuit is
shorted low.
LOOPBACK FAILURE (STORED) - MANUAL A/C
When Monitored: When the A/C - Heater Control Module executes an internal loopback
test.
Set Condition: If the A/C - Heater Control Module fails to send a message, or none of the
expected messages arrive for 5 seconds, an internal loopback test is executed. If the
internal loopback test fails, the DTC will set.
LOOPBACK TEST FAILURE (STORED) - MANUAL A/C
When Monitored: When the A/C - Heater Control Module executes an internal loopback
test.
Set Condition: If the A/C - Heater Control Module fails to send a message, or none of the
expected messages arrive for 5 seconds, an internal loopback test is executed. If the
internal loopback test fails, the DTC will set.
MODE OVERCURRENT (STORED) - MANUAL A/C
When Monitored: When actuator movement is requested.
Set Condition: All (Blend, Mode, Recirc, and Zone) Overcurrent DTCs will set if the A/C
- Heater Control Module detects an excessive current draw on the Common Door Drive
circuit(s).
515
HEATING & A/C
A/C FAULT (STORED) - MANUAL A/C ÐContinued
Page 545 of 4284

NO BCM MESSAGE RECEIVED (STORED) - MANUAL A/C
When Monitored: With the igntion on.
Set Condition: If the A/C - Heater Control Module does not receive the dimming function
message from the BCM for more than 5 seconds, then the A/C - Heater Control Module
LEDs will default to full brightness and the DTC will set.
NO PCM MESSAGE RECEIVED (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the A/C - Heater Control Module does not see any
messages from the PCM for more than 5 seconds.
PCM COMMUNICATION FAILURE (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the A/C - Heater Control Module does not receive the
Fuel message from the PCM for more than 5 seconds.
POWER FAULT (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Power switch stays closed for 10 minutes.
REAR BLEND OVERCURRENT (STORED) - MANUAL A/C
When Monitored: When actuator movement is requested.
Set Condition: All (Blend, Mode, Recirc, and Zone) Overcurrent DTCs will set if the A/C
- Heater Control Module detects an excessive current draw on the Common Door Drive
circuit(s).
REAR BLEND POT CIRCUIT OPEN (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Rear Blower Rear Control Switch, Rear Blend
Potentiometer/circuit is open.
REAR BLEND POT CIRCUIT SHORT (STORED) - MANUAL A/C
When Monitored: When the ignition is on.
Set Condition: This DTC will set if the Rear Blower Rear Control Switch, Rear Blend
Potentiometer/5 Volt Supply/Rear Temperature Feedback Signal circuit is shorted low or
high.
REAR DEFOG FAILURE (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Rear Window Defogger switch stays closed for 10
minutes.
516
HEATING & A/C
A/C FAULT (STORED) - MANUAL A/C ÐContinued
Page 546 of 4284

REAR MODE OVERCURRENT (STORED) - MANUAL A/C
When Monitored: When actuator movement is requested.
Set Condition: All (Blend, Mode, Recirc, and Zone) Overcurrent DTCs will set if the A/C
- Heater Control Module detects an excessive current draw on the Common Door Drive
circuit(s).
RECIRC OVERCURRENT (STORED) - MANUAL A/C
When Monitored: When actuator movement is requested.
Set Condition: All (Blend, Mode, Recirc, and Zone) Overcurrent DTCs will set if the A/C
- Heater Control Module detects an excessive current draw on the Common Door Drive
circuit(s).
RECIRCULATION FAULT (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the Recirc switch stays closed for 10 minutes.
TX FAILURE (STORED) - MANUAL A/C
When Monitored: When the ignition is on.
Set Condition: This DTC will set if the A/C - Heater Control Module is unable to send a
message.
UNKNOWN FAULT DETECTED (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the A/C - Heater Cotrol Module detects an internal
fault.
VEHICLE ODOMETER FAILURE (STORED) - MANUAL A/C
When Monitored: With the ignition on.
Set Condition: This DTC will set if the A/C - Heater Control Module does not receive the
Vehicle Odometer message from the PCM for more than 5 seconds.
ZONE OVERCURRENT (STORED) - MANUAL A/C
When Monitored: When actuator movement is requested.
Set Condition: All (Blend, Mode, Recirc, and Zone) Overcurrent DTCs will set if the A/C
- Heater Control Module detects an excessive current draw on the Common Door Drive
circuit(s).
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HEATING & A/C
A/C FAULT (STORED) - MANUAL A/C ÐContinued