Trips and Drive Cycles

Trips and Drive Cycles
�
Trip
A Trip is a drive cycle with specific instructions for vehicle operation within a period of time. During a Trip, all OBD II components and monitors (except the catalyst efficiency monitor) are tested at least once by the on board diagnostics system. This testing detects irregularities preventing a vehicle from meeting emission requirements.

The system monitors included in a Trip are comprehensive component monitor, misfire detection monitor, EGR system monitor, heated oxygen sensor monitor and adaptive fuel monitor. The catalyst efficiency monitor, is a steady-state monitoring system and is not part of a Trip.

Trip Display on Scan Tool
The on-board system readiness function is available on all scan tools. This function indicates the status of each OBD II monitor. One parameter identification display (PID) on a Rotunda New Generation STAR (NGS) Tester 007-00500 summarizes the status of all monitors for a TRIP SET as "Yes" or "No." A Trip must be completed to establish entry conditions necessary for the monitoring of the Catalyst Efficiency Monitor test .

Trips and Malfunction Indicator Lamp Function
Trips are used by the software strategy to control the malfunction indicator lamp (MIL) off function. The MIL is turned on after an emission related diagnostic trouble code (DTC) is stored in memory. The MIL is turned off if there are three consecutive drive cycles (refer to Description of Drive Cycles) without the identical fault under similar conditions or three Trips without the identical fault present. The actual number of drive cycles or Trips necessary to control the MIL varies with each monitor. (Refer to specific monitor description and operation.)

Trips and Diagnostic Trouble Codes
A diagnostic trouble code (DTC) will be stored in memory after the identical malfunction has been detected consecutively on at least two separate drive cycles (not necessarily completing a Trip). A misfire detection monitor DTC can be stored immediately depending on the misfire type. A catalyst efficiency monitor DTC can be stored after three identical malfunctions are detected on three separate drive cycles. A DTC will be erased from memory after 40 engine warm-up cycles, except for misfire or fuel injection system DTCs which will be cleared after 80 warm-up cycles, if the malfunction has not been detected after the malfunction indicator lamp (MIL) is turned off. DTC memory storage requirements vary with each monitor. (Refer to the specific monitor.)

Drive Cycle
A drive cycle is a method of driving a vehicle to verify a driveability symptom or its repair. It can also be a method of driving a vehicle to initiate and complete a specific OBD II monitor or Trip. A drive cycle may be done in the service bay or may require specific drive modes such as a number of idle periods, steady vehicle speed per time, accelerations at certain throttle angles, etc.

OBD II Drive Cycle
The OBD II Drive Cycle is a specific method used to perform all Trip monitor tests, as well as the catalyst efficiency monitor test. (Refer to Description of Drive Cycles.)

Trip Monitors and Catalyst Efficiency Monitor (the OBD II Drive Cycle) Requirements
The following conditions must occur to complete a Trip and test all OBD II monitors and components including the Catalyst Efficiency Monitor:
- The misfire, comprehensive component, and adaptive fuel monitors are checked continuously from engine warm-up and can complete any time.
- The exhaust gas recirculation (EGR) monitor test requires a series of idles and accelerations.
- The heated oxygen sensor (HO2S) monitor requires a steady speed drive for approximately 1 minute at 30 to 40 mph.
- The catalyst efficiency monitor requires a steady speed drive for 1 minute and 20 seconds beyond the HO2S monitor test at 40 to 65 mph.