
Symptom List:
B1800 NO START
B1801 FLAME OUT: DURING HEATING CYCLE
B1801 FLAME OUT: UNSTABLE OPERATION
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be B1800 NO START.
When Monitored and Set Condition:
B1800 NO START
When Monitored: After DCHA activation.
Set Condition: This DTC will set if the Flame Sensor resistance is not within the expected
parameters 160 sections after activation.
B1801 FLAME OUT: DURING HEATING CYCLE
When Monitored: After DCHA activation, and during subsequent start attempts.
Set Condition: This DTC will set if the Flame Sensor resistance is not within the expected
parameters.
B1801 FLAME OUT: UNSTABLE OPERATION
When Monitored: After DCHA activation.
Set Condition: This DTC will set if the Flame Sensor resistance is not within the expected
parameters.
POSSIBLE CAUSES
LOW FUEL LEVEL IN VEHICLE'S FUEL TANK
DOSING PUMP INOPERABLE, NO DOSING PUMP DTCS SET
DCHA FUEL LINE RESTRICTED/LEAKING/DAMAGED
DOSING PUMP
DCHA AIR INTAKE/EXHAUST RESTRICTED
DCHA HEATER MODULE FAULT
300
CABIN HEATER

Symptom:
B1820 DOSING PUMP CIRCUIT: OPEN OR SHORT TO BATTERY
When Monitored and Set Condition:
B1820 DOSING PUMP CIRCUIT: OPEN OR SHORT TO BATTERY
When Monitored: With the ignition on.
Set Condition: This DTC will set if the DCHA Control detects no-load voltage on the
Dosing Pump circuit output pin.
POSSIBLE CAUSES
DOSING PUMP CONTROL CIRCUIT SHORTED HIGH
DOSING PUMP CONTROL CIRCUIT OPEN
GROUND CIRCUIT OPEN
DOSING PUMP
DCHA CONTROL UNIT FAULT
TEST ACTION APPLICABILITY
1WARNING: DO NOT OPERATE THE DCHA IN AN ENCLOSED AREA SUCH
AS A GARAGE THAT DOES NOT HAVE EXHAUST VENTILATION FACILI-
TIES. ALWAYS VENT THE DCHA's EXHAUST WHEN OPERATING THE
DCHA. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN
PERSONAL INJURY OR DEATH.
WARNING: ALLOW THE DCHA ASSEMBLY TO COOL BEFORE PERFORM-
ING A COMPONENT INSPECTION/REPAIR/REPLACEMENT. FAILURE TO
FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.
CAUTION: DO NOT PERFORM THIS TEST UNLESS DIRECTED HERE BY
THE CABIN HEATER PRE-TEST. ALWAYS PERFORM THE CABIN HEATER
PRE-TEST PRIOR TO PERFORMING ANY OTHER CABIN HEATER TEST
FOR THE RESULT TO BE VALID.
NOTE: If present, diagnose and repair DTC B1811 Heater Overheated and
any other conditions relating to overheating before diagnosing this DTC.
Turn the ignition off.
NOTE: Check connectors - Clean/repair as necessary.
Disconnect the Cabin Heater Assist C1 harness connector.
Turn the ignition on.
Measure the voltage between the Dosing Pump Control circuit and ground.
Is there any voltage present?All
Ye s®Repair the Dosing Pump Control circuit for a short to voltage.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
No®Go To 2
315
CABIN HEATER

TEST ACTION APPLICABILITY
1WARNING: DO NOT OPERATE THE DCHA IN AN ENCLOSED AREA SUCH
AS A GARAGE THAT DOES NOT HAVE EXHAUST VENTILATION FACILI-
TIES. ALWAYS VENT THE DCHA's EXHAUST WHEN OPERATING THE
DCHA. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN
PERSONAL INJURY OR DEATH.
WARNING: ALLOW THE DCHA ASSEMBLY TO COOL BEFORE PERFORM-
ING A COMPONENT INSPECTION/REPAIR/REPLACEMENT. FAILURE TO
FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.
CAUTION: DO NOT PERFORM THIS TEST UNLESS DIRECTED HERE BY
THE CABIN HEATER PRE-TEST. ALWAYS PERFORM THE CABIN HEATER
PRE-TEST PRIOR TO PERFORMING ANY OTHER CABIN HEATER TEST
FOR THE RESULT TO BE VALID.
NOTE: If present, diagnose and repair DTC B1811 Heater Overheated and
any other conditions relating to overheating before diagnosing this DTC.
Turn the ignition off.
NOTE: Check connectors - Clean/repair as necessary.
Disconnect the Dosing Pump harness connector.
Turn the ignition on.
Set the Blend Control to the max cool position.
Turn the A/C - Heater Control Module's Power switch off.
With the DRBIIIt, erase Cabin Heater DTCs.
Start the engine.
Allow the engine to idle.
Turn the A/C - Heater Control Module's Power switch on.
Turn the Blower switch to the high speed position.
CAUTION: Do not activate the DCHA Field Mode Test with the engine off.
Failure to follow these instructions may result in internal damage to the
DCHA Heater Module.
NOTE: Do not disconnect the vehicle's battery or the DCHA's main power
supply while the DCHA is in operation or in run-down mode. Failure to
follow these instructions may result in excess emissions from the DCHA
during heater operation.
With the DRBIIItin Cabin Heater, Systems Tests, select Field Mode and press Enter.
Set the Blend Control to the max heat position. Upon completion of the Field Mode
Test, proceed as follows:
With the DRBIIIt, read Cabin Heater DTCs.
Turn the Blower switch off and turn the A/C - Heater Control Module's Power switch
off.
Turn the engine off.
Is DTC B1820 Dosing Pump Circuit: Short to Ground present?All
Ye s®Go To 2
No®Replace the Dosing Pump in accordance with the Service Infor-
mation.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
319
CABIN HEATER
B1820 DOSING PUMP CIRCUIT: SHORT TO GROUND ÐContinued

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.
512
HEATING & A/C

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

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

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

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