Volvo TSI, Manual

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Group 28 Design and Function
Terminating Resistor
W3002905
Terminating resistors are wired into each end of the
J1939 data link. One is located near the ABS ECU and
the other near the engine ECU. On Volvo engines, the
terminating resistor at the engine ECU end is located in-
side the EECU.
If you measure 120 ohm (+/- 10 ohm) between circuits
406 and 407, then there is only one terminatig resistor.
Check to determine which is missing and reconnect it.
Note: With Volvo engines, one terminating resistor is
within the engine ECU. The other is poitioned at the end
of the J1939 network, typically at the ABS ECU. The one
within the ECU is not accessible and should not be at
fault.
If you measure less than 60 ohm, only two terminating
resistors are used in a vehicle. Never install three in one
truck. If more than two terminating resistors exist in the
J1939 circuit, damage to the ECU electronics can occur
over time. You can easily check to see if you have two
resistors by measuring the resistance between circuits
406 and 407 with the ignition OFF. The correct resis-
tance is 60
.
The purpose of these resistors is to prevent data link
signal reflections. They must remain connected for the
system to function properly.
Communication
Equipment
(Expansion
capability)
Instrument Cluster
MIDs 234 & 140
SRS ECU
MID 232
Engine ECU
MID 128
Terminating
Resistor
Diagnostic
connector
Vehicle ECU
MID 144
SAE J1587
/1708
SAE J1939
Transmission ECU
MID 130
Control unit
(Expansion
capability)
Terminating
Resistor
ABS ECU
MID 136
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