XC90 2.5T AWD L5-2.5L Turbo VIN 59 B5254T2 (2003)
module is of use is if the customer or workshop replaced a control module with a control module from another vehicle without downloading software
For more information about the function and structure of the CAN network, further documents are available in addition to Service Manual Wiring
Design and function CAN network
See function group 37 under INFORMATION/PRODUCTSPECIFICATIONS/DESIGN AND FUNCTION.
Information about the controller area network (CAN), construction and function (TNN 37-22)
Information about the CAN network, structure and function See: Information About the CAN Network, Structure and Function
Supplementary information about faults in the CAN network (TNN 37-25)
Supplementary information about faults in the CAN network See: Supplementary Information About Faults in the CAN Network
Information about incorrect replacement (TNN 37-24)
Information about incorrect replacement See: Body and Frame/Body Control Systems/Description and Operation/Information About Incorrect
Diagnostic functions in the central electronic module (CEM)
The central electronic module (CEM) acts as a hub between the two networks. This operates as an exchange and can distribute traffic between the high
speed network (HS-CAN) and the low speed network (LS-CAN) and vice versa. The central electronic module (CEM) also contains diagnostic functions
for monitoring the traffic on the CAN network and the voltage levels in the CAN cables.
Note! The central electronic module (CEM) contains more functions for monitoring the CAN network than other control modules. For
example, the central electronic module (CEM) is the only control module that can store diagnostic trouble codes (DTCs) for short-circuits
between the CAN cables, between a CAN cable and ground and between a CAN cable and supply voltage. The fact that the central electronic
module (CEM) can do this does not mean that the central electronic module (CEM) is the cause of all faults in the CAN network. On the other
hand, other control modules can store diagnostic trouble codes (DTCs) as a result of the short-circuit. This is a small, but very important
Diagnostic trouble codes (DTCs) in pairs between the central electronic module (CEM) and a particular control module (CEM-1AXX and
Fault-tracing of the relevant control module begins if the central electronic module (CEM) has stored diagnostic trouble code (DTC) CEM-1A5X or
CEM-1A6X for an open-circuit in communication with a control module and communication cannot be established with the corresponding control
module or if the control module stored XXX-E003.
Note! If diagnostic trouble codes (DTC) can be read off from the relevant control module, the fault is probably intermittent. In the event of a
fault in the low speed network, it is particular important to investigate the junctions behind the central electronic module (CEM) and the audio
module (AUM) as well as the cable harness behind the audio module (AUM). Intermittent faults in the power supply to a control module are
indicated by a diagnostic trouble code (DTC) for a break in communication being stored in the central electronic module (CEM) (CEM-1A5X
or CEM-1A6X). There is probably no diagnostic trouble code (DTC) in the relevant control module as the control module cannot store a
diagnostic trouble code (DTC) when it is not supplied with power.
Check the supply voltage to the relevant control module
Check the ground terminal for the control module
Check the CAN cables for the control module.
Checking the power supply
A simple way to check the supply voltage and ground is to check if there is any functionality remaining in the control module. Examples of corrective
Audio module (AUM): Check whether the radio plays
Upper electronic module (UEM): Check if the seat belt reminder lights or if the sun roof works when the ignition is on
Power seat module (PSM): Check whether the seat can be moved manually
Road traffic information module (RTI): Check whether the display for the road traffic information module (RTI) can be folded up or whether a
disc can be inserted and fed out
Climate control module (CCM): Check the function. The blower fan must blow. However, the air conditioning (A/C) will not work in the event of
interrupted CAN communication.
In the event of difficulty, check as follows: Measure the supply voltage and ground terminal in the connector directly adjacent to the control module that
has stored the diagnostic trouble code (DTC).
Note! The terminals could be damaged when if readings are taken using measurement cables directly in the connector. If possible, take readings