Intermittent failures in electronic systems may be very
difficult to detect and accurately diagnose. The instrument cluster tests
for different malfunctions under different vehicle conditions. For this reason
a through test drive is often needed in order to repeat a fault condition.
If the system malfunction is not repeated during the test drive, a good description
of the complaint may be useful in locating an intermittent fault condition.
Faulty wires or connections cause most intermittent problems. When an intermittent
condition is suspected, inspect the suspected circuits for the following condition:
| • | Poor mating of connector halves of backed out terminals. |
| • | Improperly formed or damaged terminals. |
| • | Poor wire-to-terminal connections. |
| • | Dirty or corroded terminals. |
| • | Damage to connector bodies. |
History Diagnostic Trouble Codes (DTCs) are those indicating that the
instrument cluster 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 instrument cluster
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
scan tool. Read the Diagnostic Aids and Conditions for Setting the DTC in
each DTC table for more specific information.
History DTCs help in diagnosing intermittent fault conditions but do
not necessarily indicate a faculty instrument cluster. Most system complaints
are linked to faulty wiring and connectors, and occasionally to component.
Perform a through inspection of all related wiring and connectors pertaining
to the history DTC that is stored:
| • | Any condition which results in the interruption of power to the
instrument cluster. |
| • | Battery or ignition voltage that is out of range (below 9V or
above 16V). |
| • | A loose or damaged ground. |
| • | An open or short in the Class II serial data link. |
