spond to the desireddoor position. To maintain
accuracy, the system recalibrates itself period-
ically at known zero and full travel conditions.
The Single-Zone HVAC system uses:
• one, two-wire electric blend door actuator.
• two, two-wire electric mode door actuators.
• one, two-wire electric recirculation door actuator.
The Dual-Zone HVAC system uses:
• two, two-wire electric blend door actuators.
• two, two-wire electric mode door actuators.
• one, two-wire electric recirculation door actuator.
3.9.3 SYSTEM REVISIONS
The 2004 DR, HVAC system remains carryover
from 2003.
3.9.4 SYSTEM DIAGNOSTICS
Fault detection is through active and stored Diag-
nostic Trouble Codes (DTCs)
• DTCs are displayed by the DRBIIIt.
• Active 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.
• Stored DTCs are those which occurred in the
system since the A/C-Heater Control Module re-
ceived the last 9clear diagnostic info9 message.
The A/C Cooldown Test:
• is actuated with the DRBIIIt.
• checks A/C system performance based on evapo-
rator temperature sensor input.
• will not run if ambient temperature is below
12.7°C (55°F).
• will pass if the evaporator temperature drops
6.7°C (20°F) within two minutes of starting the
test.
• faults display on the DRBIIIt as test messages
only after running the test.
• faults will not display on the DRBIIIt as Diag-
nostic Trouble Codes.
• will cause theA/C mode switch status indicator to
flash while the test is running.
• If the test fails, the status indicator will con-
tinue to flash until either the test returns
passed or the ignition key is cycled. It will also
prevent the EBL mode switch status indicator
from indicating EBL operating status. How-
ever, the EBL mode switch will continue to
function in this state.
The HVAC Door Recalibration function:
• is actuated with the DRBIIIt.
• monitors for door span faults.
• faults display on the DRBIIIt as test messages
only after running the test.
• faults will not display on the DRBIIIt as Diag-
nostic Trouble Codes.
• will cause the EBL mode switch status indicator
to flash while the test is running.
• If the test fails, the status indicator will con-
tinue to flash until either the test returns
passed or the ignition key is cycled. It will also
prevent the A/C mode switch status indicator
from indicating A/C operating status. How-
ever, the A/C mode switch will continue to
function in this state.
The Actuator Circuit Test:
• is actuated with the DRBIIIt.
• monitors for shorted actuator circuits.
• allows service to easily diagnose and troubleshoot
up to three simultaneous shorts.
• supplements the continuous diagnostics on the
actuator drive system.
• faults display on the DRBIIIt as test messages
only after running the test.
• faults will not display on the DRBIIIt as Diag-
nostic Trouble Codes.
When Performing The Actuator Circuit Test
CAUTION: To ensure a proper diagnosis,
repair all Short Too Complex messages first,
all common door driver circuit related
messages second, and all other door driver
circuit related messages last.
CAUTION: The DRBIIIT can display up to
three Actuator Circuit Test messages at a
time. After repairing each Actuator Circuit
Test message, cycle the ignition switch, then
rerun the Actuator Circuit Test to ensure no
new messages exist.
• The Short Too Complex message:
• indicates that a specific determination of
which lines are shorted could not be made.
• is caused by more than three drivers being
shorted in the same direction. For example,
four drivers all shorted to ground, or two or
more drivers shorted with at least one driver
shorted to ignition/battery and one driver
shorted to ground.
• Messages displaying:
• XXX Driver/Circuit Shorted to Ignition/
Battery will set on a per-driver basis.
• XXX Driver/Circuit Shorted to Ground will set
on a per-driver basis.
• the same two drivers/circuits shorted to
14
GENERAL INFORMATION
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