Intermittent faults in electronic systems may be very difficult
to detect and to diagnose accurately. The Body Control Module (BCM) tests
for different malfunctions under different vehicle conditions. For this reason,
a thorough test drive is often needed in order to repeat a fault condition.
If the system malfunction is not repeated during the drive test, a good description
of the complaint may be useful in locating an intermittent fault condition.
Also, perform tests while moving related wiring and connectors. This can often
cause the malfunction to reoccur.
Faulty wires or connections cause most intermittent problems. When an
intermittent condition is suspected, inspect the suspected circuits for these
conditions:
| • | Poor mating of connector halves, or backed out terminals. |
| • | Improperly formed or damaged terminals. |
| • | Poor wire to terminal connections. |
| • | Dirty or corroded terminals. |
History Diagnostic Trouble Codes (DTCs) are those indicating that the
BCM has previously detected a malfunction. The reason could be either that
the malfunction is intermittent or that the system for which the DTC is set
for is not currently being operated. If the BCM displays history DTCs and
the malfunction cannot be found easily, try clearing the DTCs and manually
operating the system that the DTC applies to using a Tech 2 scan tool. Read
the diagnostic aids and conditions for setting the DTC in each DTC table for
more specific information. Perform a thorough inspection of all related wiring
and connectors pertaining to the history DTC that is stored.
The following conditions may result in intermittent BCM operation with
no DTCs stored:
| • | Any condition which results in the interruption of power to the
BCM. |
| • | The battery voltage is out of range (below 9V or above 16V). |
| • | A loose or damaged ground. |
