Drive Cycles

Drive Cycles

A number of different drive cycles are defined by OBD legislation for fault diagnosis. Each drive cycle is a precise routine which the engine or vehicle must undergo to produce the conditions that enable the ECM to perform diagnostic routines. T4 can be used to view the status and results of the diagnostic routines performed by the ECM. When a fault code is stored, it will indicate, via T4 and the Diagnostic P code list, the drive cycle required to verify a repair.

When a fault has been rectified and the fault P codes cleared from the applicable ECU using T4, the following drive cycles must be performed to ensure that the fault has been corrected and to ensure that no other fault codes are subsequently stored. The above P Code table shows the applicable drive cycle required when a particular P code has been recorded.

WARNING: Ensure that the drive cycles are performed in a safe area and do not endanger other road users. Observe all local highway laws when performing the drive cycles.

The following drive cycle procedures relate to the drive cycle letters shown in the Diagnostic P Code table

Drive Cycle A
1. Move the ignition switch to position II for 30 seconds.
2. Make sure that the engine coolant temperature is less than 60 degree C (140 degree F).
3. Start the engine and allow to idle for 2 minutes.
4. With T4 connected to the vehicle diagnostic socket, check for fault codes.
5. Investigate and rectify any fault codes found and perform the relevant drive cycle procedure for the fault codes.

Drive Cycle B
1. Move the ignition switch to position II for 30 seconds.
2. Make sure that the engine coolant temperature is less than 60 degree C (140 degree F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform two light accelerations (0 to 35 mph with light throttle pedal pressure).
5. Perform two medium accelerations (0 to 45 mph with moderate throttle pedal pressure)
6. Perform two hard accelerations (0 to 55 mph with heavy throttle pedal pressure).
7. With the vehicle stationary, allow the engine to idle for 2 minutes.
8. With the engine still running and T4 connected to the vehicle diagnostic socket, check for fault codes.
9. Investigate and rectify any fault codes found and perform the relevant drive cycle procedure for the fault codes.

Drive Cycle C
1. Move the ignition switch to position II for 30 seconds.
2. Make sure that the engine coolant temperature is less than 60 degree C (140degree F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform two light accelerations (0 to 35 mph with light throttle pedal pressure).
5. Perform two medium accelerations (0 to 45 mph with moderate throttle pedal pressure)
6. Perform two hard accelerations (0 to 55 mph with heavy throttle pedal pressure).
7. Cruise at a constant 60 mph for 8 minutes.
8. Cruise at a constant 50 mph for 3 minutes.
9. With the vehicle stationary, allow the engine to idle for 3 minutes.
10. With the engine still running and T4 connected to the vehicle diagnostic socket, check for fault codes.
11. Investigate and rectify any fault codes found and perform the relevant drive cycle procedure for the fault codes.

Drive Cycle C+
1. This is an extended Drive Cycle C to enable the internal diagnostic process to be completed which is not achieved by Drive Cycle C. Perform this additional drive cycle after the 3 minute idle is completed and when prompted by T4.
2. Perform medium acceleration to 60 mph and hold for 10 seconds.
3. Release the throttle pedal and allow the vehicle to decelerate to 50 mph.
4. Perform a second medium acceleration to 60 mph and hold for 10 seconds.
5. Release the throttle pedal and allow the vehicle to decelerate to 50 mph.
6. Repeat steps 4 and 5 a further 13 times until 15 acceleration/decelerations cycles have been performed.
7. With the engine still running and T4 connected to the vehicle diagnostic socket, check for fault codes.
8. Investigate and rectify any fault codes found and perform the relevant drive cycle procedure for the fault codes.

NOTE: DRIVE CYCLE C and C+ - Faults in the following areas also have an associated 'Readiness Test' that must be flagged as 'completed' before the technician can verify that the problem in that are is rectified:

- Catalytic Converter fault
- Evaporative Loss System (EVAP) fault
- HO2S fault
- HO2S heater fault.

Although these tests are normally completed within Drive Cycle C, select the 'Readiness Test' icon on the T4 screen to verify that the test has been flagged as completed.

Drive Cycle D
1. Move the ignition switch to position II for 30 seconds.
2. Make sure that the engine coolant temperature is less than 60 degree C (140 degree F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform two light accelerations (0 to 35 mph with light throttle pedal pressure).
5. Perform two medium accelerations (0 to 45 mph with moderate throttle pedal pressure)
6. Perform two hard accelerations (0 to 55 mph with heavy throttle pedal pressure).
7. Cruise at a constant 60 mph for 5minutes.
8. Cruise at a constant 50 mph for 5minutes.
9. Cruise at a constant 35 mph for 5minutes.
10. With the vehicle stationary, allow the engine to idle for 2 minutes.
11. With the engine still running and T4 connected to the vehicle diagnostic socket, check for fault codes.
12. Investigate and rectify any fault codes found and perform the relevant drive cycle procedure for the fault codes.

Drive Cycle E
1. Make sure that the fuel tank is at least 1/4 (25%) full.
2. Perform Drive Cycle A.
3. Switch off the engine and allow the vehicle rest undisturbed for 20 minutes.
4. Move the ignition switch to position II.
5. With T4 connected to the vehicle diagnostic socket, check for fault codes.
6. Investigate and rectify any fault codes found and perform the relevant drive cycle procedure for the fault codes.

Drive Cycle F
1. For P codes requiring this drive cycle, T4 will provide guidance to force the actuator or function through a diagnostic routine to confirm correct operation.