XC70 L5-2.5L Turbo VIN 59 B5254T2 (2003)
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
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.
Abbreviations and terms
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LS-CAN. Low speed network in the car. In practice this is restricted to the passenger compartment and the cargo compartment
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HS-CAN. High speed network in the car. In practice this is restricted to the engine compartment
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CAN-H. CAN cable with the higher voltage. The voltage oscillates between 2.5 V and approximately 3.5 V when there is traffic on the CAN
network
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CAN-L. CAN cable with the lower voltage. The voltage oscillates between 2.5 V and approximately 1.5 V when there is traffic on the CAN
network.
