Freelander: Siemens Engine Management System Overview
ENGINE MANAGEMENT SYSTEM - SIEMENS
DESCRIPTION AND OPERATION 18-4-39
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. TestBook/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 TestBook/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 TestBook/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
°
C (140
°
F).
3 Start the engine and allow to idle for 2 minutes.
4 With TestBook/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
°
C (140
°
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 TestBook/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
°
C (140
°
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 TestBook/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.