Manufacturer Drive Cycle
Drive Cycle
The following diagram shows how a drive cycle is set (test drive) in order for all the systems to be monitored once. The test conditions can be created in any desired order after start-up.
Example of a Drive Cycle for Completing all OBD II Relevant Checks
1. Engine cold start, idling, approximately 3 minutes. Evaluated:
^ Secondary Air System
^ Evaporative Leak Detection (LDP Equipped Vehicles)
2. Constant driving at 20 to 30 MPH, approximately 4 minutes. Evaluated:
^ Oxygen Sensors - Achieved "Closed Loop" Operation
^ Oxygen Sensors - Response Time and Switching Time (Control Frequency)
3. Constant driving at 40 to 60 MPH, approximately 15 minutes (sufficient vehicle coasting phases included). Evaluated:
^ Catalytic Converter Efficiency
^ Oxygen Sensors - Response Time and Switching Time (Control Frequency)
4. Engine idling, approximately 5 minutes. Evaluated:
^ Tank-Leak Diagnosis (DM TL Equipped Vehicles after KL 15 is switched OFF)
NOTE: The diagnostic sequence illustrated above will be interrupted if:
^ The engine speed exceeds 3000 RPM
^ Large fluctuations in the accelerator pedal position. The driving speed exceeds 60 MPH
The "Malfunction Indicator Light" (MIL) will be illuminated under the following conditions:
^ Upon the completion of the next consecutive driving cycle where the previously faulted system is monitored again and the emissions relevant fault is again present.
^ Immediately if a "Catalyst Damaging" fault occurs (Misfire Detection).
The illumination of the light is performed in accordance with the Federal Test Procedure (FTP) which requires the lamp to be illuminated when:
^ A malfunction of a component that can affect the emission performance of the vehicle occurs and causes emissions to exceed 1.5 times the standards required by the (FTP).
^ Manufacturer-defined specifications are exceeded.
^ An implausible input signal is generated.
^ Catalyst deterioration causes HG-emissions to exceed a limit equivalent to 1.5 times the standard (FTP).
^ Misfire faults occur.
^ A leak is detected in the evaporative system, or "purging" is defective.
^ ECM fails to enter closed-loop oxygen sensor control operation within a specified time interval.
^ Engine control or automatic transmission control enters a "limp home" operating mode.
^ Ignition is on (KL1 5) position before cranking = Bulb Check Function.
Within the BMW system the illumination of the Malfunction Indicator Light is performed in accordance with the regulations set forth in GARB mail-out 1968.1 and as demonstrated via the Federal Test Procedure (FTP). The following page provides several examples of when and how the Malfunction Indicator Light is illuminated based on the "customer drive cycle".
1. A fault code is stored within the ECM upon the first occurrence of a fault in the system being checked.
2. The "Malfunction Indicator Light" will not be illuminated until the completion of the second consecutive "customer driving cycle" where the previously faulted system is again monitored and a fault is still present or a catalyst damaging fault has occurred.
3. If the second drive cycle was not complete and the specific function was not checked as shown in the example, the ECM counts the third drive cycle as the "next consecutive" drive cycle. The "Malfunction Indicator Light" is illuminated if the function is checked and the fault is still present.
4. If there is an intermittent fault present and does not cause a fault to be set through multiple drive cycles, two complete consecutive drive cycles with the fault present are required for the "Malfunction Indicator Light" to be illuminated.
5. Once the "Malfunction Indicator Light" is illuminated it will remain illuminated unless the specific function has been checked without fault through three complete consecutive drive cycles.
6. The fault code will also be cleared from memory automatically if the specific function is checked through 40 consecutive drive cycles without the fault being detected or with the use of either the DIS, GT-1 or Scan tool.
Note: In order to clear a catalyst damaging fault (see Misfire Detection) from memory, the condition must be evaluated for 80 consecutive cycles without the fault reoccurring.
With the use of a universal scan tool, connected to the "OBD" DLC an SAE standardized DTC can be obtained, along with the condition associated with the illumination of the "Malfunction Indicator Light". Using the DISplus or GT-1, a fault code and the conditions associated with its setting can be obtained prior to the illumination of the "Malfunction Indicator Light".
System Monitoring
Within the framework of OBD II, certain components/systems must be monitored once per driving cycle while other control systems (e.g. misfire detection) must be monitored permanently. A "driving cycle" consists of engine start-up, vehicle operation (exceeding of starting speed), coasting and engine stopping.
Permanent Monitoring
Permanently monitored Systems are monitored according to temperature immediately after start-up. In the event of malfunctions (e.g. oxygen sensor), the Malfunction Indicator Light will illuminate immediately.
The following are monitored permanently:
^ Misfire Detection
^ Fuel System (duration of injection)
^ All emission related electrical circuits, components and systems of the ECM, 1CM and EML (if equipped).
Cyclic Monitoring
Systems monitored once per driving cycle will only result in a fault being registered after the corresponding operating conditions have been completed. Therefore, there is no possibility for checking when the engine is started up briefly and then shut down.
The following are monitored once per driving cycle:
^ Oxygen Sensor Function
^ Secondary Air Injection System
^ Catalytic Converter Function (efficiency)
^ Evaporative Vapor Recovery System
Due to the complexity involved in meeting the test criteria within the defined driving cycle, all tests may not be completed within one "customer driving cycle". The test can be successfully completed within the defined criteria, however customer driving styles may differ and therefore may not always monitor all involved components/systems in one "trip".