Diagnostic Trouble Code (DTC) Readout

The engine control module is equipped with DTC memory. Malfunctions are recognized and stored as DTC's and are categorized as those that occur:

- Continuously,
- Longer than 3 seconds,
- Intermittent contact failures that occur 5 times during a trip).

The DTC's will remain stored in memory even if the vehicle battery is disconnected.

In the event of a component malfunction, e.g. the engine coolant temperature sensor, the control module selects a substitute value or enters a fixed operating mode. Operation of the fuel injection and ignition system thereby remains largely unaffected. Malfunctions which are no longer present in the system are automatically erased after 19 trips. A trip is defined as:

- Vehicle speed > 2.5 mph (4 km/h),
- Engine speed > 700 rpm,
- Engine is turned OFF for at least 30 seconds.

The stored DTC's can be read at the diagnostic connector using either an impulse counter scan tool or the Hand-Held Tester (HHT) (See Computers and Control Systems, System Diagnosis).

Note: Diagnosis via an on-off ratio readout has been eliminated.