L322 Range Rover System Description and Operation
BODY CONTROL UNIT
86-3-8
DESCRIPTION AND OPERATION
Diagnostics
Diagnostic monitoring is included in the operating software of the BCU and is performed on a continual basis. All of
the input and output signals which are relevant for diagnostics can be read out and injected using TestBook/T4.
Detected faults are stored in the non volatile memory (EEPROM) of the BCU.
All faults stored by the BCU are stored chronologically, with a fault counter, in a fault or information area of the
memory. Faults which positively point to one or more defective components are stored in the fault area. Faults which
do not positively point to a defective component are stored in the information area to provide information during
troubleshooting. The BCU ignores faults detected within 32 seconds of power up or when battery voltage is less than
9 V.
A distinction is made between sporadic and static faults. Sporadic faults are those which have occurred at least once,
and the cause of the fault message was no longer present at least one time. Static faults are faults which are still active
at the time diagnostics are performed.
The BCU can store up to 30 faults at any one time. If further faults are detected following the 30th fault they are
ignored. Faults can only be erased using TestBook/T4.
Up to 16 faults stored by the BCU are also stored in those modules connected to the BCU via the P bus, i.e. the driver
and passenger door modules and the sunroof module. Faults stored in the peripheral modules cannot be accessed
via the diagnostic socket. The faults in the peripheral modules are used for diagnosing modules after they are
removed from the vehicle.