L322 Range Rover System Description and Operation
ENGINE MANAGEMENT SYSTEM – V8
18-2-38 DESCRIPTION AND OPERATION
Several 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, the drive cycle required to verify a repair.
The ECM only records a fault after it has occurred on more than one drive cycle. This fault strategy is referred to as
debouncing. When it is first detected, a fault is stored as a temporary fault. If the fault recurs within the next 40 warm-
up cycles, the fault is stored as a permanent fault and freeze frame data for the second occurrence is recorded. If the
fault does not recur within the next 40 warm-up cycles, the ECM deletes the temporary fault from memory.
The ECM illuminates the MIL when requested to do so by the EAT ECU, to perform a bulb check when the ignition is
switched on and for any emissions related fault. There is no MIL illumination for non emission related engine
management faults.
Resetting the adaptions will clear all adaptions from the ECM memory.
Drive Cycles
TestBook/T4 drive cycles are as follows:
Drive cycle A
1 Switch on the ignition for 30 seconds.
2 Ensure engine coolant temperature is less than 60
°
C.
3 Start the engine and allow to idle for 2 minutes.
4 Connect TestBook/T4 and check for fault codes.
Drive cycle B
1 Switch ignition on for 30 seconds.
2 Ensure engine coolant temperature is less than 60
°
C.
3 Start the engine and allow to idle for 2 minutes.
4 Perform 2 light accelerations, i.e. 0 to 35 mph with light pedal pressure.
5 Perform 2 medium accelerations, i.e. 0 to 45 mph with moderate pedal pressure.
6 Perform 2 hard accelerations, i.e. 0 to 55 mph with heavy pedal pressure.
7 Allow engine to idle for 2 minutes.
8 Connect TestBook/T4 and, with the engine still running, check for fault codes.
Drive cycle C
1 Switch ignition on for 30 seconds.
2 Ensure engine coolant temperature is less than 60
°
C.
3 Start the engine and allow to idle for 2 minutes.
4 Perform 2 light accelerations, i.e. 0 to 35 mph with light pedal pressure.
5 Perform 2 medium accelerations, i.e. 0 to 45 mph with moderate pedal pressure.
6 Perform 2 hard accelerations, i.e. 0 to 55 mph with heavy pedal pressure.
7 Cruise at 60 mph for 8 minutes.
8 Cruise at 50 mph for 3 minutes.
9 Allow engine to idle for 3 minutes.
10 Connect TestBook/T4 and, with the engine still running, check for fault codes.
The following areas have an associated readiness test which must be flagged as complete, before a problem
resolution can be verified:
l
Catalytic converter fault.
l
Evaporative loss system fault.
l
HO2S fault.
l
HO2S heater fault.
When carrying out drive cycle C to determine a fault in any of the above areas, select the readiness test icon to verify
that the test has been flagged as complete.