XC70 L5-2.5L Turbo VIN 59 B5254T2 (2003)
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.
General procedure
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Check the supply voltage to the relevant control module
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Check the ground terminal for the control module
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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
action:
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Audio module (AUM): Check whether the radio plays
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Upper electronic module (UEM): Check if the seat belt reminder lights or if the sun roof works when the ignition is on
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Power seat module (PSM): Check whether the seat can be moved manually
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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
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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
on the rear of the connector. If this is not possible, use a loose terminal strip to insert in the connector.
Diagnostic testing of main arteries in the low speed network (LS-CAN)
Measure the resistance between the controller area network (CAN) cables in the connector for the power seat module (PSM) if applicable (these are easy
to access). Otherwise connect the breakout box at the central electronic module (CEM) or at the driver information module (DIM). The advantage of
using the breakout box is that it is possible to check the functionality of the entire network with all control modules connected.
The resistance reading only checks the main path in the LS-CAN. The resistance reading does not check the divergence paths such as the road traffic
information module (RTI), accessory electronic module (AEM), power seat module (PSM), phone module (PHM), audio module (AUM), driver door
module (DDM) and passenger door module (PDM). See the relevant wiring diagram, Data communication for clarification. However, resistance readings
between the two CAN cables can show if there is a short-circuit between the two cables (or their junctions). A normal value, measured somewhere in the
middle of the network, is between 55 and 65 ohms when all control modules are connected (120 ohms parallel connected). Twist and bend the cable
harness at suitable points to detect any intermittent fault causes.
Note! Resistance 60 ohms can only be measured if the main artery is intact and connected in the part of the CAN network in which the reading
is taken. If there is an open circuit anywhere along the main artery or if any control module through which the main artery passes (a control
module with four CAN connections) is not connected, resistance will be 120 ohms when the reading is taken. For more information, see the
wiring diagram.
Also take resistance readings between each CAN cable and the supply voltage and ground. Twist and bend the cable harness at suitable points to detect
any intermittent fault causes. The resistance must be infinite or very high (higher than 1 Mohms).
Hint: Both readings can be taken in the same connector if the CAN cables, power supply and ground are exposed. If possible, take readings on the rear
of the connector to prevent damage to the terminals in the connector. If this is not possible, use the adapter wiring or loose terminal pins to obtain a good
contact. The resistance must be infinite or very high (higher than 1 Mohms).
If the main artery is OK (i.e. approximately 60 ohms measured in the power seat module (PSM), for example), measure the resistance in the CAN cables
from the relevant control module.
Diagnostic testing of main arteries in the high speed network (HS-CAN)
In principle it is only possible to measure the resistance in the high speed network (HS-CAN) using adapter wiring. It is easiest to connect the adapter
wiring at the engine control module (ECM). Connect the engine control module (ECM) again to the adapter wiring to obtain the correct values when
taking readings. The resistance must be approximately 60 ohms.
Note! Resistance 60 ohms can only be measured if the main artery is intact and connected in the part of the CAN network in which the reading
is taken. If there is an open circuit anywhere along the main artery or if any control module through which the main artery passes (a control
