DESCRIPTION : Code F30 is set if the BCM is unable to receive data from the Electronic Climate Control panel (ECC). Code F31 indicates that the same condition exists between the BCM and Fuel Data Center (FDC). If a malfunction should occur in a circuit common to both display panels, both codes will be stored in BCM memory. Due to the failure modes of codes F30 and F31, they will only be displayed if the problem is intermittent. When these codes are currently failing, the displays do not function properly which prohibits the use of diagnostics. Listed below are the symptoms and malfunctions which would result in one or both codes being displayed after the problem corrects itself.
One or more of the following symptoms is associated with each circuit malfunction and is referenced in parentheses: Panel displays "D"
Panel displays "C"
Panel frozen, dim or blank
Displays flash "ON" and "OFF"
Code F30 Only: ECC - BCM Data Problem: CKT 718 open or short to ground (1)
ECC branch of CKT 713 open (2)
ECC branch of CKT 751 open (3)
ECC branch of CKT 705 open (3)
Faulty ECC (1, 2, 3 or 4)
Faulty BCM (1)
Code F31 only: FDC - BCM Data Problem: CKT 719 open or short to ground (1)
FDC branch of CKT 713 open (2)
FDC branch of CKT 751 open (3)
FDC branch of CKT 705 open (3)
Faulty FDC (1, 2, 3 or 4)
Faulty BCM (1)
Both codes F30 and F31: Symptoms Affect Both Displays: Common branch of CKT 713 is open (2)
CKT 713 short to ground (2)
Common branch of CKT 751 open (3)
Common branch of CKT 705 open (3)
CKT 705 short to ground (3, 4)
Faulty BCM (1, 2, 3, 4)
NOTE ON INTERMITTENTS : If an intermittent code F30 and or F31 is being set, manipulate the related wiring while observing the display panels. If the failure is induced, the associated symptom will appear. This will help to isolate the location of the malfunction. If the failure is indicated but cannot be isolated to a given circuit, follow the SELF-DIAGNOSTIC CIRCUIT CHECK, which is designed to locate display malfunctions which are currently failing.
Thats the flow chart. Not an easy diag and requires someone with expierence to determine the failure.