On-Board Diagnostics

A diagnostic test is a series of steps, the result of which is a pass or fail reported to the Diagnostic Executive. When a diagnostic test reports a pass result, the Diagnostic Executive records following data:

• Diagnostic test has been completed since last ignition cycle.
• Diagnostic test has passed during current ignition cycle.
• Fault identified by diagnostic test is not currently active.

When a diagnostic test reports a fail result, the diagnostic executive records the following data:

• Diagnostic test has been completed since last ignition cycle.
• Fault identified by diagnostic test is currently active.
• Fault has been active during this ignition cycle.
• Operating conditions at time of failure.

A fuel trim DTC may be triggered by a list of vehicle faults. Make use of all information available (other DTCs stored, rich or lean condition, etc.) when diagnosing a fuel trim fault.