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OBD II diagnostics

OBD II diagnostics

Terms

Trip

Starting the engine and then driving in such a way that all components and functions included in the OBD II diagnostics have been monitored.

Driving cycle

Starting the engine.

Warming-up cycle

Starting the engine and then an increase in engine temperature of at least 22 °C (40 °F) to at least 71 °C (160 °Ø).


Similar operating conditions

• engine speed ±375 rpm

• engine load ±10 %

• same heat status (under or over 71 °C (160 °F))


Enable criteria

Conditions that must be fulfilled before the diagnosis is performed.

Fault criteria

Once enable criteria have been fulfilled, the diagnosis will check whether the fault criteria have been fulfilled.

Dependents

Once fault criteria have been fulfilled, it may sometimes be necessary for other diagnoses to report OK before the diagnostic trouble code is generated.

System reaction to a fault

Once the fault criteria have been fulfilled, certain measures will sometimes be taken.

OK report

The diagnosis can be included as a dependent for another diagnosis and must therefore report OK even if it is continuous. The OK report is also used in fault handling to decrease the fault counter.

Fault handling, throttle control

If a safety-related fault should occur in the throttle control, the throttle body will go into mechanical limp-home mode and CHECK ENGINE will immediately go on. The limp-home solenoid is subsequently activated each time the ignition is turned on. The fault will not repair itself and the car must be rectified in a workshop.

After repairing, the diagnostic trouble code must be cleared first and then the limp-home mechanism reset.