Definition of Terms

Definition of Terms

Warm-up cycle
The warm-up cycle is the time which the engine requires to reach operating temperature. To fulfill the warm-up cycle condition, the engine temperature on start-up must not be higher than a specified value (e.g. 30 °C). The engine operating phase has to be long enough to reach a specified temperature (e.g. 70 °C). The warm-up cycle condition is needed to count down or reduce the erase counter in the case of faults which have been recognized as corrected.

Driving cycle
A driving cycle consists of starting the engine, running the engine or driving until oxygen sensing becomes active, and then stopping the engine. Since the system cannot know when the engine will be stopped, the diagnostic routines are started as soon as oxygen sensing is activated.

Trip
A trip is a driving cycle after a rest period that enabled the diagnostic system to monitor all components and systems at least once. In the event of a fault, it may not be possible to perform all diagnostic routines under certain circumstances. For this reason, a replacement trip is recognized after an operating period of 1150 seconds. In other words, a driving cycle is recognized as a trip after this time, even if not all diagnostic routines were performed.

Readiness code
The readiness code indicates that the required fault checks were performed by the OBD system. It is not important whether or not a fault was found. The readiness code is reset if the fault memory is erased or the power supply (terminal 30) is cut off when a code is stored. The readiness code is not reset when the battery is disconnected if no fault is stored. To initiate the readiness code, at least two trips have to be completed.

The readiness code is shown for the following systems:
- Catalytic converter conversion
- Fuel tank ventilation system
- Secondary air system
- Oxygen sensor
- Oxygen sensor heating

Freeze frame
Freeze frame data are the momentary operating conditions that are recorded in the memory when a fault occurs. Only freeze frame data of one fault are stored in this way. If no fault has been recorded, the freeze frame data of the first fault are recorded. If a special fault occurs (misfire or a fault in the fuel supply system), the freeze frame data already recorded are overwritten. If an additional special fault occurs, the freeze frame data of the first special fault remain in the memory. These freeze frames are only displayed with a generic scan tool.

The following operating conditions can be recorded:
- DTC of the fault which initiated storage of freeze frame data
- Oxygen sensing status, bank 1
- Oxygen sensing status, bank 2
- Load value
- Engine temperature
- Oxygen sensing value FR, bank 1
- Adaptation value FRA, bank 1
- Oxygen sensing value FR2, bank 2
- Adaptation value FRA 2, bank 2
- Engine rpm
- Vehicle speed

Fault shedding
When a fault is recognized during a diagnostic routine, it is stored as a suspected fault. At the same time, a fault shedding counter is started that contains a certain value. During additional diagnostic routines, the shedding counter will be decreased by 1 if the fault is recognized in the same area window. If the shedding counter has reached the value 0, the fault is considered as shedded.

Fault healing
When a fault is recognized during a diagnostic routine, it is stored as a suspected fault. At the same time a fault healing counter is started that contains a certain value. During additional diagnostic routines, the fault healing counter will be decreased by 1 if the fault is not recognized in the same area window. If the fault healing counter has reached the value 0, the fault is considered to be healed. If the fault has triggered the Fault Indicator Lamp (MIL) then the latter is switched off as long as it is not triggered by any further faults.

Fault erasing counter
For each recognized fault, an individual fault erasing counter is kept. The counter determines the memory storage time of the respective fault.
The first time the fault is recognized, the fault erasing counter is set to 80.
If an unshedded fault is recognized as healed, the fault erasing counter is set to 40. Each time a shedded fault is recognized, the fault erasing counter is set to 10. It retains this value until fault healing is recognized.
After each warm-up operating cycle the fault erasing counter is decreased by 1, when the fault in question is recognized as unshedded or healed. When the fault erasing counter reaches the value 0, the fault is erased from the memory.