Definitions
Warm up cycle:
The warm-up cycle is the time for the engine to warm up. To fulfill the condition "warm-up cycle", the engine temperature may not be higher than a specified value (for instance 30°C). The engine operating phase has to be long enough to reach a specified temperature (for instance 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 stopping the engine. Since stopping the engine cannot be predetermined, the diagnostic routines are started as soon as the 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 all diagnostic routines were not performed.
Readiness code:
The "readiness code" indicates that the required fault checks were performed by the OBD system. It is not important whether a fault was found. The readiness code is cancelled if the fault memory is erased or the power supply (terminal 30) is cut off with a code 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.
For the following systems the "readiness code is shown:
- Three Way Catalytic Converter (TWC) converting
- Fuel tank ventilation system
- Secondary air injection system
- Oxygen sensor
- Oxygen sensor heating
Freeze Frame:
"Freeze frames" are the momentary operating conditions that are recorded to memory when a fault occurs. Only "freeze frames of a fault are recorded to memory. If no fault has been recorded, the "freeze frames" of the first fault are recorded. If a special fault occurs (misfire or a fault in the fuel supply system), the faults already recorded are overridden. If an additional fault is recognized, the freeze frames of the first special fault remain in memory. These freeze frames are only displayed by the scan tool.
The following operating conditions are recorded:
- Trouble code of 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 speed
- Vehicle speed
Fault shedding:
When a fault is recognized during a diagnostic routine, it will be stored as a possible fault. At the same time a "not shedded" fault counter is started that contains a certain value. At additional diagnostic routines, the "not shedded" fault counter will be decreased by 1 if the fault is recognized in the same channel window. If the "not shedded" fault counter has reached the value 0, the fault is considered as shedded.
Fault healing:
When a fault is recognized during a diagnostic routine, it will be stored as a possible fault. At the same time a fault-healing counter is started that contains a certain value. At additional diagnostic routines, the fault healing counter will be decreased by 1 if the fault is not recognized in the same channel window. If the fault-healing counter has reached the value 0, the fault is considered to be healed. If the fault has triggered the Malfunction Indicator Lamp (MIL) then the MIL is switched off as long as no further fault triggers the MIL.
Fault erasing counter:
For each recognized fault, a respective fault erasing counter is kept. The counter determines the memory storage time of the respective fault. At the first recognition of the fault, the fault-erasing counter is set to 80.
If a fault is healed that was recognized as "not shedded", the fault erasing counter is set to 10. Each time a "not shedded" fault is recognized, the fault erasing counter is set to 10. At each recognition of a "not shedded" fault, the fault-erasing counter is set to 40. It retains this value up to the recognized fault healing.
The fault-erasing counter is decreased by 1 after each warm-up cycle, when it involves a "not shedded" fault or a fault that was recognized as healed.
When the fault erasing counter reaches the value 0, the fault will be erased from memory.