Chrysler Town, Dodge Caravan. Manual — part 828
Symptom:
LOOPBACK TEST FAILURE (ACTIVE) - MTC
When Monitored and Set Condition:
LOOPBACK TEST FAILURE (ACTIVE) - MTC
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.
POSSIBLE CAUSES
ADDITIONAL CODE(S) PRESENT
A/C - HEATER CONTROL MODULE
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRBIII
t, read HVAC DTCs.
Does the DRBIII
t display any additional HVAC DTCs?
All
Yes
→ Return to the symptom list and choose the symptom(s).
Perform BODY VERIFICATION TEST - VER 1.
No
→ Replace the A/C - Heater Control Module in accordance with the
Service Information.
Perform BODY VERIFICATION TEST - VER 1.
548
HEATING & A/C
Symptom List:
NO FUEL LEVEL MESSAGE RECEIVED (ACTIVE) - MTC
PCM COMMUNICATION FAILURE (ACTIVE) - MTC
VEHICLE ODOMETER FAILURE (ACTIVE) - MTC
Test Note:
All symptoms listed above are diagnosed using the same tests.
The title for the tests will be NO FUEL LEVEL MESSAGE
RECEIVED (ACTIVE) - MTC.
When Monitored and Set Condition:
NO FUEL LEVEL MESSAGE RECEIVED (ACTIVE) - MTC
When Monitored:
With the ignition on.
Set Condition:
This DTC will set if the A/C - Heater Control Module does not receive the
Fuel Level message from the PCM for more than 5 seconds.
PCM COMMUNICATION FAILURE (ACTIVE) - MTC
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.
VEHICLE ODOMETER FAILURE (ACTIVE) - MTC
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.
POSSIBLE CAUSES
MESSAGE NOT RECEIVED
ATTEMPT TO COMMUNICATE WITH THE PCM/ECM
PCI BUS CIRCUIT OPEN
POWERTRAIN/ENGINE CONTROL MODULE
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRBIII
t, enter HVAC, System Tests then PCM Monitor.
Does the DRBIII
t display: PCM is active on BUS?
All
Yes
→ Replace the A/C - Heater Control Module in accordance with the
Service Information.
Perform BODY VERIFICATION TEST - VER 1.
No
→ Go To 2
549
HEATING & A/C
TEST
ACTION
APPLICABILITY
2
Turn the ignition on.
With the DRBIII
t, attempt to communicate with the PCM/ECM.
Was the DRBIII
t able to communicate with the PCM/ECM?
All
Yes
→ Go To 3
No
→ Refer to Communication for the related symptom(s)
Perform BODY VERIFICATION TEST - VER 1.
3
Turn the ignition off.
Disconnect the PCM C2/ECM C1 harness connector. Read the following caution if
vehicle is equipped with NGC.
CAUTION: DO NOT PROBE THE PCM HARNESS CONNECTORS. PROBING
THE PCM HARNESS CONNECTORS WILL DAMAGE THE PCM TERMI-
NALS RESULTING IN POOR TERMINAL TO PIN CONNECTION. INSTALL
MILLER SPECIAL TOOL #8815 TO PERFORM DIAGNOSIS.
Disconnect the DRBIII
t from the Data Link Connector (DLC).
Disconnect the negative battery cable.
Measure the resistance of the PCI Bus circuit between the Data Link Connector
(DLC) and the PCM C2/ECM C1 connector.
Is the resistance below 5.0 ohms?
All
Yes
→ Replace and program the Powertrain/Engine Control Module in
accordance with the Service Information.
Perform BODY VERIFICATION TEST - VER 1.
No
→ Repair the PCI Bus circuit for an open.
Perform BODY VERIFICATION TEST - VER 1.
550
HEATING & A/C
NO FUEL LEVEL MESSAGE RECEIVED (ACTIVE) - MTC —
Continued
Symptom:
REAR BLEND POT CIRCUIT OPEN (ACTIVE) - MTC
When Monitored and Set Condition:
REAR BLEND POT CIRCUIT OPEN (ACTIVE) - MTC
When Monitored:
With the ignition on.
Set Condition:
This DTC will set if the A/C - Heater Control Module sees voltage above
4.88 volts on the Rear Temperature Feedback Signal circuit.
POSSIBLE CAUSES
5 VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
CHECK REAR TEMPERATURE FEEDBACK SIGNAL CIRCUIT VOLTAGE
REAR TEMPERATURE FEEDBACK SIGNAL CIRCUIT OPEN
A/C - HEATER CONTROL MODULE
5 VOLT SUPPLY CIRCUIT SHORTED TO REAR TEMPERATURE FEEDBACK SIGNAL CIRCUIT
REAR TEMPERATURE RETURN CIRCUIT OPEN
REAR BLEND POTENTIOMETER
A/C - HEATER CONTROL MODULE
TEST
ACTION
APPLICABILITY
1
Turn the ignition off.
Disconnect the Rear Blower Rear Control Switch C2 harness connector.
Turn the ignition on.
Measure the voltage of the 5 Volt Supply circuit.
Is the voltage above 5.3 volts?
All
Yes
→ Repair the 5 Volt Supply circuit for a short to voltage.
Perform BODY VERIFICATION TEST - VER 1.
No
→ Go To 2
2
Turn the ignition off.
Disconnect the Rear Blower Rear Control Switch C2 harness connector.
Turn the ignition on.
Measure the voltage of the Rear Temperature Feedback Signal circuit.
What voltage is present?
All
Above 5.1 Volts
Repair the Rear Temperature Feedback Signal circuit for a short
to voltage.
Perform BODY VERIFICATION TEST - VER 1.
Below 0.25 Volts
Between 0.25 & 5.1 Volts
551
HEATING & A/C
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