Symptom:
LOOPBACK TEST FAILURE (ACTIVE)
When Monitored and Set Condition:
LOOPBACK TEST FAILURE (ACTIVE)
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
CHECK FOR ADDITIONAL HVAC DTCS
A/C - HEATER CONTROL MODULE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read HVAC DTCs.
Does the DRBIIIt display 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.
221
HEATING & A/C
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